Shorter Contributions 

to Geochemistry, 

1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER
Shorter Contributions 

to Geochemistry, 

1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-A-I

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

Shorter contributions to geochemistry.

(Geological Survey professional paper ; 1129-A-1129-I)

Includes bibliographies.

CONTENTS: Sherrill, N. D., and Dalrymple, G. B. A computerized multichannel data acquisition and control 

system for high-precision mass spectrometry. Cannon, H. L., and Swanson, V. E. Contributions of 

major and minor elements to soils and vegetation by the coal-fired Four Corners Power Plant, San Juan 

County, New Mexico. Bunker, C. M., Hedge, C. E., and Sainsbury, C. L. Radio-element concentrations 

and preliminary radiometric ages of rocks of the Kigluaik Mountains, Seward Peninsula, Alaska, [etc.]

Supt. of Docs, no.: I 19.16:1129

1. Geochemistry Addresses, essays, lectures. I. Series United States. Geological Survey. Professional 

paper ; 1129-A-1129-I.

QE515.S486 551.9 79-607041

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402

Stock Number 024-001-03299-6
CONTENTS

[Letters designate the chapters]

(A) A computerized multichannel data acquisition and control system for high-precision 

mass spectrometry, by Nathaniel D. Sherrill and G. Brent Dalrymple.

(B) Contributions of major and minor elements to soils and vegetation by the coal-fired 

Four Corners Power Plant, San Juan County, New Mexico, by Helen L. 

Cannon and Vernon E. Swanson

(C) Radioelement concentrations and preliminary radiometric ages of rocks of the 

Kigluaik Mountains, Seward Peninsula, Alaska, by Carl M. Bunker, Carl E. 

Hedge, and C. L. Sainsbury

(D) Chemical variability of a metavolcanic rock unit in the Tracy Arm-Fords Terror 

Wilderness Study Area, Alaska, and the definition of background values for 

geochemical purposes, by J. D. Hoffman, D. A. Brew, C. L. Forn, and B. R. 

Johnson

(E) Efficient stream-sediment sampling design: an experiment at Tracy Arm, Alaska, 

by Bruce R. Johnson, Carl L. Forn, James D. Hoffman, David A. Brew, and 

Constance J. Nutt

(F) Indirect determination of chloride in plants by atomic-absorption spectrophotometry, 

by John B. McHugh and James H. Turner

(G) Determination of iridium and ruthenium in geological samples by fire assay and 

emission spectrography, by Joseph Haffty, A. W. Haubert, and N. J. Page

(H) Complexity of titaniferous magnetites from Essex County, New York, as a hindrance to beneficiation by a method based on Curie temperature differences, by 

Harry Klemic and Patrick J. Loferski

(I) A technique for the decomposition and dissolution of rocks and the determination of 

lithium, calcium, and magnesium using atomic-absorption spectroscopy, by 

Alien L. Meier
CONVERSION FACTORS

Metric unit Inch-Pound equivalent

Length

millimeter (mm) 

meter (m) 

kilometer (km)

= 0.03037 inch (in) 

= 3.28 feet (ft) 

= .62 mile (mi)

Area

square meter (m2 ) 

square kilometer (km2 ) 

hectare (ha)

= 10.76 square feet (ft2 ) 

= .386 square mile (mi2 ) 

= 2.47 acres

Volume

cubic centimeter (cm3 ) 

liter (L) 

cubic meter (m^) 

cubic meter 

cubic hectometer (hms) 

liter 

liter 

liter 

cubic meter

cubic meter

= 0.061 cubic inch (in3 ) 

= 611.03 cubic inches 

= as.ai cubic feet (ft3 ) 

= .00081 acre-foot (acre-ft) 

= 810.7 acre-feet 

= 2.113 pints (pt) 

= 1.06 quarts (qt) 

= .26 gallon (gal) 

= .00026 million gallons (Mgal or 

10« gal) 

= 6.290 barrels (bbl) (1 bbl = 42 gal)

Weight

gram (g) 

gram 

metric tons (t) 

metric tons

= 0.035 ounce, avoirdupois (oz avdp) 

= .0022 pound, avoirdupois (Ib avdp) 

= 1.102 tons, short (2,000 Ib) 

= 0.9842 ton, long (2,240 Ib)

Specific combinations

kilogram per square 

centimeter (kg/cm2 ) 

kilogram per square 

centimeter 

cubic meter per second 

(m«/s)

 0.96 atmosphere (atm)

 .98 bar (0.9869 atm) 

= 35.3 cubic feet per second (fts/s)

Metric unit

Specific

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[(m3/s)/km2 ] 

meter per day (m/d)

meter per kilometer 

(m/km) 

kilometer per hour 

(km/h) 

meter per second (m/s) 

meter squared per day 

(m2/d) 

cubic meter per second 

(m?/s)

cubic meter per minute 

(ma/min)

liter per second (L/s) 

liter per second per 

meter [(L/s)/m] 

kilometer per hour 

(km/h) 

meter per second (m/s) 

gram per cubic 

centimeter (g/cm3 ) 

gram per square 

centimeter (g/cm2 ) 

gram per square 

centimeter

Inch-Pound equivalent

combinations Continued

= .0353 cubic foot per second 

= 91.47 cubic feet per second per 

square mile [(fts/s)/mi2 ]

rr 3.28 feet per day (hydraulic 

conductivity) (ft/d) 

= 5.28 feet per mile (ft/mi)

 .9113 foot per second (ft/s)

 3.28 feet per second

= 10.764 feet squared per day (ft2/d) 

(transmissivity) 

= 22.826 million gallons per day 

(Mgal/d) 

= 264.2 gallons per minute (gal/min)

= 15.85 gallons per minute 

= 4.83 gallons per minute per foot 

[(gal/min) /ft]

 .62 mile per hour (mi/h)

= 612.43 pounds per cubic foot (lb/ft3 ) 

= 2.048 pounds per square foot (lb/ft2 ) 

= .0142 pound per square inch (lb/in2 )

Temperature

degree Celsius (°C) 

degrees Celsius 

(temperature)

= 1.8 degrees Fahrenheit (°F) 

= [(1.8x°C)+32] degrees Fahrenheit
A Computerized Multichannel

Data Acquisition and Control System

for High-Precision Mass Spectrometry

By NATHANIEL D. SHERRILL and G. BRENT DALRYMPLE

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-A

CONTENTS

	Page 

Abstract ____________________________________________ Al

Introduction -___________________________________ 1

Hardware configuration ___________________________________ 1

Software ___________________________________ 3

Clock wait function CKW(N) ___________________________ 3

Control function CTL(M,N) ____________________________ 3

Read data function RDA(N) ______________________________ 4

Sample program ___________________________________ 4

ILLUSTRATIONS

Page

FIGURE 1. Block diagram of multichannel data system with elapsed-time counter ______________________ _________ A2

2. Diagram showing the bit assignment and word format for the argument M in the control function

CTL(M,N) ___________.______________________________________ ________________ 4

III

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

A COMPUTERIZED MULTICHANNEL 

DATA ACQUISITION AND CONTROL SYSTEM 

FOR HIGH-PRECISION MASS SPECTROMETRY

By NATHANIEL D. SHERRILL and G. BRENT DALRYMPLE

ABSTRACT

The hardware and assembly language software for a simple multichannel digital data system has been built around 

a 12-bit minicomputer. The system is capable of controlling 

an external device and taking data simultaneously from as 

many as five data channels and an elapsed-time counter. 

Input of 0 to 10 volts to the data channels provides six significant decimal digits for computation. Although the system 

was designed for use with mass spectrometers, it could easily 

be adapted, with little or no change in either the hardware 

or software, to a variety of analytical instruments; it could 

also be easily expanded to include additional channels.

INTRODUCTION

Mass spectrometry.for geochronological and isotopic tracer studies requires data of high precision 

over a dynamic signal range of more than 105 . As 

examples, 10Ar/3GAr isotope ratios for potassiumargon dating are frequently more than 104 , and the 

precision required for S7Sr/8G Sr ratios are typically 

better than 1 part in 7000. Input signals to the data 

system may range from less than 0.1 millivolt to 10 

volts dc. We have designed and constructed a relatively simple and versatile computerized control and 

data acquisition system that not only meets these 

requirements of precision and dynamic range, but 

also is capable of acquiring data simultaneously 

from as many as five data channels and keeping 

track of elapsed time during an analysis.

The system is designed around a dedicated Digital Equipment Corporation l (DEC) PDP8/E 12-bit 

minicomputer and uses DEC logic hardware and 

programing languages. Both control and data acquisition are by programed input/output via three 

PALS assembly language functions that are called

1 Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the 

U.S. Geological Survey.

directly from OS/8 BASIC, which makes programing the system very easy for the user. The software 

does not expect the external devices to set deviceready flags, which simplifies the necessary hardware 

and the interfacing of the external devices to the 

computer system. Data from the system are input 

with a 23-bit mantissa giving six significant decimal 

digits for computation. The elapsed-time counter 

can be reset and will record intervals of from 0.02 s 

to more than 46 h; integration times are precise to 

better than 0.0002 s. The dynamic range of the system permits integration times as long as 8 s at 10 V 

signal input without overflowing the digital data 

counters.

Although the system was designed for use with 

mass spectrometers, it could easily be adapted, with 

little or no change in either the hardware or software, to a variety of analytical instruments; it could 

also be easily expanded to include additional channels. The assembly language routines could also be 

rewritten in the assembly languages RALF or 

SABR for use with FORTRAN IV or II, respectively, with no changes in hardware configuration, 

and most if not all of the system concept could be 

adapted to other minicomputer or microcomputer 

systems.

HARDWARE CONFIGURATION

For single-channel operation, the system can be 

configured as in figure 1. Our system has four additional but identical data channels. Input signals of 

0 to 10 V dc are fed to a Teledyne Philbrick model 

470501 voltage to frequency converter (V/F), which 

has a transfer characteristic of 1-MHz (megahertz) 

output for a 10 V dc input and a linearity of 0.05 

percent or better over its entire range. The output

Ai
A2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

50 Hz

DK8EC 

crystal clock

LATCH

HrIh > 

M236

12-bit - 

counter

Carry 

^

LA

M

M1705 

output interface

Voltage to frequency 

converter

_______ff_________J

INPUT SIGNAL 

(0-10 volts d c )

FIGURE 1. Block diagram of multichannel data system with elapsed-time counter. Only one of the five data channels is 

shown. Control paths (output from the computer bus) are shown as single lines; data paths (input to the computer 

bus), as double lines.

of the V/F is fed to two DEC M236 12-bit counters 

that are cascaded so that the carry-out signal of the 

low-order counter is a count input to the high-order 

counter. Each counter is read independently by the 

computer through its own DEC M1703 input interface and the low-order and high-order 12-bit words 

combined internally by the software into a standard 

PDP8 23-bit floating-point number. Counting control is via one channel of a DEC M1705 dual channel 

12-bit output interface. One bit per data channel is 

used to set counter outputs to zero via the counter 

LOAD DATA connection. Because all counter 

DATA INPUTS are permanently grounded, receipt

of a LOAD DATA command (LOGIC LOW) from 

the output interface causes all zeros to appear on 

the counter outputs. When LOAD DATA is released, 

the counters will respond to any pulse that are 

present at the COUNT IN terminal.

A design restriction of the counters prohibits 

changing the state of the ENABLE input, which 

starts and stops the counter, except when the count 

in pulse is in the high state. The 350-nanosecond 

width of the input pulses would require extensive 

gating in order to use the ENABLE input, and so it 

was decided to gate the output of the V/F with a 

high-speed optical isolator and leave the counters
A COMPUTERIZED DATA ACQUISITION AND CONTROL SYSTEM FOR MASS SPECTROMETRY A3

permanently enabled. The choice of an optical isolator (Litronix model IL-100), in addition to providing control of the V/F signal to the counters, 

offers the opportunity to isolate the analog and digital grounds, thereby reducing system noise.

The second channel of the output interface is used 

to control the beam deflection magnet field strength 

via a 12-bit digital to analog converter (DAC), 

which produces an output voltage proportional to 

the digital input code. This voltage is compared to 

the output of a gaussmeter by an operational amplifier that drives the magnet power supply to produce 

the field value represented by the digital code.

Timing is provided by a nonprogramable DK8EC 

quartz crystal clock. The 5-kHz output from the 

clock is fed directly to the computer bus where it is 

available to the software for timing of integration 

times and program delays. The 50-Hz output is fed 

to the two cascaded 12-bit counters in the elapsedtime (E-T) counter. The output from each counter 

drives a 12-bit latch that can be latched on command 

via the M1705 output interface. This latch allows the 

count to be read via the two M1703 input interfaces 

without interrupting the elapsed-time counters, 

which continue to operate. On command to unlatch, 

the latches assume the current counter output states. 

To reset the elapsed-time counter, the counters are 

zeroed, but, like the data counters, they are always 

left enabled.

SOFTWARE

The software for the system consists of three assembly language functions, CKW(N), CTL(M,N), 

and RDA (N), that are written in PALS and called 

as user-defined functions from OS/8 BASIC 

(BASIC ver. 5A, OS/8 ver. 3D). An annotated list 

of these functions is given at the end of this report. 

Details about PALS, OS/8 BASIC, and instructions for interfacing the functions to the BASIC 

Run-Time System (BRTS) are given in the Digital 

Equipment Corporation OS/8 Handbook (Maynard, 

Mass., Digital Equipment Corp.).

CLOCK WAIT FUNCTION—CKW(N)

The clock wait function causes a simple delay in 

the execution of a BASIC program and is called as a 

statement of the form

Y = CKW(N),

where Y is a dummy variable and N specifies the 

decimal number of clock pulses before the function 

returns to the main program. For mass spectrometry, the function is used to time integration intervals and to delay the program in order to allow the 

magnetic field to settle after the DAC has been 

switched to a new value.

Because the argument N is passed to the software 

counter as a 12-bit word, its value is restricted to 

the range O^N^4095. The frequency of the crystal 

clock output is 5 kHz, but in order to increase the 

precision of the function without severely limiting 

the maximum interval length, the software counters 

within CKW(N) make it appear to the user as if 

the clock is running at 50 Hz. This arrangement results in a clock resolution of 0.02 percent for a 1-s 

delay (±1 count at 5 kHz), a minimum specifiable 

delay interval of 0.02 s (N = l), and a maximum 

delay interval of 81.9 s (N = 4095). Note that the 

program delays caused by the function, although 

precise, are actually a little longer than specified 

(that is, a 50-count delay will be slightly longer than 

1 s) because of the execution time of the function 

software. The error, however, is less than 1 millisecond and is negligible for most applications, particularly when a constant integration time is used 

throughout a single program. If the CKW(N) function is to be used for precise timing, for example, 

integration times, the user functions must be in core 

before the first data are taken or significant timing 

errors will occur while BRTS executes the overlay.

CONTROL FUNCTION—CTL(M,N)

The control function is used to pass a bit pattern 

to an external device by setting the bits of either of 

the two digital output registers of the M1705 output 

interface. The function is called with a dummy variY = CTL(M,N)

able and uses two decimal arguments, O^N^l 

where 0 = channel A and 1 = channel B, and O^M^ 

4095 is the bit pattern to be passed. For our application, channel A is used to control the magnet by 

passing a bit pattern, which specifies the field 

strength, to the magnet control system.

Channel B is used to control the data system and 

the elapsed-time (E-T) counter. Each channel, including the E-T counter, requires only two bits for 

complete control so all six channels can be controlled 

independently with a single command by passing 

the proper bit pattern to channel B of the output 

interface. The bit assignments for the argument M 

are shown in figure 2. As an example of the flexibility of this system, the decimal argument 2298 (100 

Oil 111 010 binary or 4372 octal) would latch the 

E-T counter outputs, reset the data counters for 

channel 5 to zero, gate on the V/Fs for channels 3
A4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

M = 3072 = E-T 

M = 4095 = E-T

and 4, and gate off the V/Fs for channels 1 and 2. 

In practice, however, only a few arguments are 

necessary because, for most applications, the five 

data channels are controlled simultaneous.

M = 1024 = E-T counter reset to zero, data counters

reset to zero

counter outputs unlatched, data

counters reset to zero

counter outputs unlatched, V/F

gated on 

M = 2730 = E-T counter outputs latched, VF gated

off

Note that these same arguments work equally well 

with a system of less than five data channels because the commands for the missing channels are 

simply ignored.

READ DATA FUNCTION—RDA(N)

The read data function is used to read the five 

data channels and the E-T counter. It is called from 

BASIC in the form

Y = RDA(N),

where O^N^S specifies the channel to be read according to the channel assignments in figure 2. The 

function returns with the value (either data or E-T 

count) in the mantissa of the 23-bit floating point 

accumulator, and that value is assigned to the variable Y, which may be treated as any other decimal 

variable.

SAMPLE PROGRAM

An example of the use of these functions for mass 

spectrometer control and data acquisition is illustrated in the following annotated BASIC program 

segment.

220 Y=CTL (2241,0)

230 Y=CKW(200)

240 Y=CTL (1024,1)

250 Y=CTL (4095,1)

260 Y=CKW(150)

270 Y=CTL(2730,1)

280 T=50*RDA(0)

290 X1=RDA(1)

300 X2=RDA(2)

/switch magnet to new field 

strength

/wait 4 s for field to settle

/reset E-T and data counters to 

zero

/gate V/Fs on

/integrate 3s

/gate V/Fs off, latch E-T counter 

outputs

/read elapsed time in seconds, assign value to variable T

/read data channel 1, assign to 

variable XI

/read data channel 2, assign to 

variable X2

List of functions

/CKW____CLOCK WAIT

/BASIC FUNCTION THAT CAUSES A DELAY IN 

/PROGRAM EXECUTION USING THE DK8-EC 

/REAL-TIME CLOCK. FUNCTION USES ONE 

/ARGUMENT 0<=N<=4095 TO SPECIFY THE 

/NUMBER OF CLOCK COUNTS BEFORE RETURNING 

/TO THE MAIN BASIC PROGRAM. CHANGE DELAY 

/FOR CLOCK FREQUENCIES AS FOLLOWS: 

/50HZ=777, 500HZ=7770, 5KHZ=7634. 

/2-19-76 G. BRENT DALRYMPLE, U.S.G.S.

CHANNEL 0 5 

FUNCTION Elapsed-time Data 5

4 

Data 4

3 

Data 3

2

Data 2 Data 1

10 11

WORD 

FORMAT

OReset 

1 = NOP

CHatch 

l=Unlatch

0=Reset 

1=NOP

0=0ff 

1 = On

BIT PATH

FROM To M236 

OUTPUT LOAD DATA 

INTERFACE in P ut

To latch 

enable

To M236

LOAD DATA

input

To optical 

isolator gate

FIGURE 2. Bit assignment and word format for the argument M in the control function CTL(M,N). The bit assignments 

data channel 1 and the E-T counter are shown; all five data channels are identical.
A COMPUTERIZED DATA ACQUISITION AND CONTROL SYSTEM FOR MASS SPECTROMETRY A5

CKW,

AGAIN, 

WAIT,

COUNTR, 

DELAY,

INTL=156 

CLSK=6133

FIELD 0

*3400

0

CLA

JMS I INTL

CIA

DCA COUNTR

TAD DELAY

DCA DCOUNT

CLSK

JMP .-1

ISZ DCOUNT

JMP WAIT

ISZ COUNTR 

JMP AGAIN 

JMP I CKW 

0 

7634

/BRTS POINTER TO

UNSFIX 

/CLOCK SKIP ON FLAG

IOT

/ENTRY POINT

/FIX ARG TO INTEGER

IN AC

/NEGATE INTEGER 

/STORE AS COUNTER 

/SET DELAY COUNTER

/WAIT FOR CLOCK FLAG

/DONE COUNTING? 

/NO. WAIT FOR

ANOTHER FLAG 

/DONE COUNTING? 

/NO 

/YES. RETURN TO BASIC

/-100(10) FOR 5KHZ 

CLOCK

DCOUNT, 0

/CTL ____ CONTROL

/BASIC FUNCTION TO SET THE BITS OF THE

/DIGITAL OUTPUT REGISTERS OF A M1705

/OUTPUT INTERFACE, FUNCTION USES TWO

/ARGUMENTS (M,N). 0<-N<=1 WHERE 0=

CHANNELA

/AND 1=CHANNEL B. 0<=M< =4095(10)

/SPECIFIES THE BIT PATTERN TO BE PASSED

/10-18-74. G. BRENT DALRYMPLE, U.S.G.S.

CTL,

INTL=156

IArrl465

FGETL=157

ARGPRE=311

INSAV=56

*3450

0

CLA

JMSIINTL

DCA VALUE 

JMS GETARG 

JMSIINTL

CIA 

IAC 

SPA 

JMPIA

CIA 

IAC

/BRTS POINTER TO

UNSFIX 

/BRTS ILLEG ARG ERROR

MESSAGE 

/BRTS POINTER TO

FFGET 

/BRTS SUB TO LOCATE

SCALAR VAR 

/SCALAR LOG USED BY

ARGPRE

/ENTRY POINT

/FIX ARG M TO INTEGER

IN AC 

/SAVE M

/PUT N INTO FAC 

/FIX ARG N TO INTEGER

IN AC

/NEGATE N 

/IS N<=1?

/NO. FATAL ERROR 

MESSAGE

/YES 

/RECOVER N

WRITE,

RTL

RAL

TAD WRTCHA

DCA WRITE

TAD WRITE

TAD K0001

DCA STROBE

TAD VALUE

0

NOP

STROBE, 0

CLA

JMP I CTL

/ROTATE

/THREE LEFT

/MAKE M1705 WRITE IOT

/DCA IOT

/RECOVER WRITE IOT

/MAKE STROBE IOT

/DCA STROBE IOT

/RECALL M

/OUTPUT DIGITAL

VALUE 

/ALLOW DATA TO

SETTLE 

/STROBE DATA TO

DEVICE

/RETURN TO BASIC

/SUBROUTINE BORROWED FROM DEC UF.8E 

/ENTER WITH SCALAR (0=ARG2, 1=ARG3, 2=ARG4) 

/IN AC: RETURN WITH ARG IN FAC

GETARG, 0

KARG,

VALUE, 

WRTCHA,

K0001,

DCA INSAV 

JMS I KARG 

JMSIFGETL 

ARGPRE

CDF

JMP I GETARG

0

6153

/USED BY ARGPRE 

/GET ADR OF ARG 

/PUT ARG IN FAC 

/THIS LOG SKIPPED BY

FFGET

/RESET DATA FIELD 

/RETURN 

/M STORAGE 

/M1705 WRITE IOT, CHAN

A

/RDA __ READ DATA

/BASIC FUNCTION TO READ UP TO N 23-BIT DATA

/CHANNELS USING TWO M236 12-BIT COUNTERS

/IN SERIES AND TWO M1703 INPUT INTERFACES

/PER CHANNEL. 0<=N<=5. FUNCTION RETURNS TO

/BASIC WITH DATA IN FAC.

/REVISED 5-17-76. G. BRENT DALRYMPLE, U.S.G.S.

RDA,

EXP=44 

HORD=45 

LORD=46 

INTL-156

FNORL=124

IA=1465

K0010=177

*3520

0

CLA

JMS I INTL

CIA

TAD K0005

SPA

JMPIA

CIA

TAD K0005

RTL

/FAC LOCATIONS

/BRTS POINTER TO

UNSFIX 

/BRTS POINTER TO

FFNOR 

/BRTS ILLEG ARG ERROR

MESSAGE 

/CONSTANT 10 (BRTS

LOG)

/ENTRY POINT

/FIX ARG TO INTEGER

IN AC 

/NEGATE ARG

/IS N<=5?

/NO. FATAL ERROR

MESSAGE 

/YES

/RECOVER N 

/MULT N X 2 AND
A6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

RDDAL,

RTL

TAD RDDAO

DCA RDDAL

0

DCA LORD

TAD RDDAL

TAD K0010

DCA RDDAH

/ROTATE 3 LEFT 

/MAKE LO ORD READ

IOT

/DEPOSIT IOT 

/READ LO ORDER BITS 

/DEPOSIT IN FAC 

/RECOVER IOT 

/MAKE HI ORDER READ

IOT 

/DEPOSIT IOT

RDDAH, 0

DCA HORD 

TAD K0027 

DCA EXP 

JMS I FNORL 

JMP I RDA

RDDAO, 6424

K0027, 

K0005,

27

5

/READ HI ORDER BITS 

/DEPOSIT IN FAC 

/PUT 23 (10) INTO EXP

/NORMALIZE FAC 

/RETURN TO BASIC 

/M1703 READ IOT, LO 

ORD, CH 0

/23(10)
Contributions of Major and Minor Elements 

to Soils and Vegetation by 

the Coal-Fired Four Corners Power Plant, 

San Juan County, New Mexico

By HELEN L. CANNON and VERNON E. SWANSON

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-B

CONTENTS

Abstract ____________________________

Introduction ________________________

Sampling plan _____________________

Sampling and analytical techniques __. 

Coal and coal-combination products 

Soils ____________________ 

Vegetation _____________________

Summary and conclusions ____________

References cited ____________________

Page

Bl

1

3

3

4

5

5

8

13

ILLUSTRATIONS

FIGURE 1. Map showing sample localities in relation to the Four Corners Power Plant, northwestern New Mexico

2. Photograph of the Four Corners Power Plant, from ths east side of Lake Morgan __________________

3. Photograph of view to the west from the Four Corners Power Plant along traverse A -A' toward the 

ash-disposal ponds ___________________________ ____________________________ _________ __

4. Photograph of view looking west at the Navajo mine spoil piles from a station on traverse C-C' _____

5. Graph showing elemental components of coal and stack products of the Four Corners Power Plant __

6. Graphs of elemental concentration in top 12 mm of soils determined from sample pairs collected at stations along three traverses away from the Four Corners Power Plant _______________________

7. Graph showing concentrations of some elements in San Juan County vegetation collected in 1961 and 

1971 compared with concentrations in the average shrub ____________-__-__---_---_--__ _____

Page

B2

2

3

3

6

12

TABLES

TABLE 1. Analytical methods used and lower limits of detection shown for selected elements ________________

2. Average major-oxide composition of ash of coal used at the Four Corners Power Plant and of coal used 

in the entire southwestern United States ________ ___________________________________________

3. Inorganic composition of soils collected from two stations _________________________________________

4. Composition of vegetation collected at various distances from the Four Corners Power Plant _________

5. Fluorine analyses of soils and vegetation in relationship to the Four Corners Power Plant __________

Page

B4

5

7

10

12

ill

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

CONTRIBUTIONS OF MAJOR AND MINOR ELEMENTS TO

SOILS AND VEGETATION BY THE COAL-FIRED 

FOUR CORNERS POWER PLANT, SAN JUAN COUNTY, NEW MEXICO

By HELEN L. CANNON and VERNON E. SWANSON

ABSTRACT

The major chemical components in the ash from the Four 

Corners coal-fired power plant in San Juan County, N. Mex., 

are Al»03 , SiO,, K-0, CaO, MgO, Na,0, and Fe,<X Many 

minor elements, including Sb, As, F, Hg, Se, Te, U, and 

Zn are enriched in the fly ash relative to the bottom ash or 

coal. Except for F and Hg, particulate effluvium collected 

from the crowns of shrubs near the power plant has lower 

concentrations of the enumerated minor elements than does 

the fly ash collected within the generating station; F and 

Hg show a relative enrichment in the effluent. In the vicinity 

of the power plant, the fly ash is currently contributing 

major and minor elements that are essential to vegetative 

growth to otherwise deficient soils. The concentrations of 

potentially harmful minor elements, such as Hg, As, Cd, 

and Pb, that originate at the power plant drop off rapidly 

with distance from the stacks and, at distances greater 

than 3 km, are lower than the average contents in United 

States soils. Pb concentrations in samples collected near 

highways and Hg in samples taken near gas-well fittings are 

higher than the concentrations in samples collected near the 

power plant. Vegetation even within 3 kilometers of the 

Four Corners Power Plant contains only normal concentrations of those elements considered to be hazardous to livestock or to man.

INTRODUCTION

By 1971, the people of Farmington and Shiprock, 

the Navajo tribe, and State officials in New Mexico 

had become concerned about the large quantities of 

smoke issuing from the stacks of the Four Corners 

Power Plant built near Fruitland, in San Juan 

County (fig. 1). A few people expressed concern 

about possible widespread destruction and contamination of large areas of the Southwest by the strip 

mines and power plants slated to be opened in the 

near future. To address these concerns and to provide facts on which thoughtful decisions could be 

based, and because most of the coal to be used as

fuel for these plants would be mined on Federal 

lands, the U.S. Department of the Interior initiated 

a multiagency project called the Southwest Energy 

Study. Three parts of this study were principally the 

responsibility of the U.S. Geological Survey: (1) to 

estimate and evaluate the coal resources in southwest United States (Averitt and others, 1972), (2) 

to determine the composition of the coal to be mined 

for use in the 10 power plants either anticipated or 

already in production (Swanson, 1972), and (3) to 

determine the effects of the effluent from the Four 

Corners Power Plant on the composition of soils 

and vegetation in the surrounding area (Cannon 

and Anderson, 1972) (fig. 2). The latter task was 

also a responsibility of EPA (U.S. Environmental 

Protection Agency).

The 2,170-megawatt Four Corners Power Plant 

was built by the Arizona Public Service Co. as operator for a combine of several power companies. It 

is located on a semiarid mesa south of the San Juan 

River on a relatively unpopulated part of the Navajo 

Indian Reservation. The mesa, which is capped by 

the Pictured Cliffs Sandstone of Cretaceous age 

(Fassett and Hinds, 1971), supports a sparse 10- 

percent cover of low xerophytic shrubs and grasses 

growing under semiarid conditions. The dry unproductive land near the power station has attracted 

few inhabitants and has been used by the Navajos 

only for sheep grazing. The artificial Lake Morgan, 

which supplies cooling water for the power station, 

has changed the appearance of the area and is 

stocked with fish. However, blue-green algae are 

now growing in the lake and are potentially toxic 

to fish (EPA, written commun., 1975). The Quaternary terrace alluvium along the nearby San Juan

Bl
B2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

I09C

45 30 15 108 ,0 n

San Juan 

A Power Plant

A A

Fruitland

I

SHIP ROCK

30

Farminqton Dam of

\Navajo Reservoir

Four Corners 

Power Plant

10 15 KILOMETERS

EXPLANATION 

O Soil sample

x Vegetation 

sample

At ripi ex sample

Vegetation and 

soil samples

Soil traverse

FIGURE 1. Map showing sample localities in relation to the Four Corners Power Plant, northwestern New Mexico.

FIGURE 2. View of the Four Corners Power Plant, looking 

west from the east side of Lake Morgan.

River is irrigated and cultivated for garden vegetables, fruit, alfalfa, and field corn. The towns of 

Shiprock, Fruitland, and Farmington are within 32 

km of the plant. At the time of our study in 1971, 

the plant was releasing 300,000 kg of particulate 

matter per day to the atmosphere when all four 

units were operating; corrective measures since 

taken at considerable expense have substantially reduced that amount.

The annual precipitation at Fruitland is 177 mm 

a year, the amount of rainfall being greatest in late 

summer and early fall. The presence of "black 

alkali" prevents infiltration to the ground-water 

table, as does the commonly torrential nature of the
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO B3

rains, which results in rapid runoff rather than 

penetration to the water table. Predominant wind 

directions, influenced by the orientation of the valley of the San Juan River, are from both east and 

west; the wind commonly blows from the east in 

the morning as cold air drains from the San Juan 

Mountains and reverses directions in the warm 

afternoons. Plume release from the power plant is 

at 91.4 m.

The objectives of the ecologic impact study were 

(1) to study the products of combustion and the 

composition of coal used in the power plant, (2) to 

collect and analyze samples of soils and vegetation 

from the San Juan County stations that had been 

studied in 1961-62 before the power plant was constructed, and (3) to reanalyze the older samples for 

comparison with the present collection.

Only 11 of the original stations were within 24 

km of the power plant, and therefore additional soil 

and plant samples were collected along several new 

traverses both east and west from the plant for distances sufficient to obtain background samples. 

Plants collected along traverses A-A' and B-B' (fig. 

1) were restricted to xerophytic species of Atriplex 

(A. confertifolia, A. nuttali, A. powelli, and A. corrugata) having similar habits of ion uptake. The 

eastern traverse, C C', was extended for a distance 

of about 80 km. Species of grass and sage were collected on traverse C-C' along the San Juan River. 

These included Oryzopsis hymenoides, Sporobolus 

airoides, Calamagrostis inexpansa, and Artemisia 

tridentata. The samples most contaminated were collected 3.2 km directly west of the power plant in an 

ash-slurry disposal area, which is ditched to ponds 

at the end of traverse A-A' (fig. 3). The east

FIGURE 3. View to the west from the Four Corners Power 

Plant along- traverse A-A' toward the ash-disposal ponds.

FIGURE 4. View looking- west at the Navajo mine spoil piles 

from a station on traverse C-C'.

traverse, C-C', crossed the spoil piles of the Navajo 

mine and continued east to Navajo Lake (fig. 4).

The analyses showed that the earlier soil samples, 

from which ground splits had been saved, contained 

more metal than did later samples, because of improvements made in grinding equipment since the 

earlier samples had been ground. The two sets of 

soil samples, therefore, could not be compared for 

the purposes of this study. Both sets of vegetation 

samples, however, were ground in the same mill, 

were not washed, and therefore could be compared.

SAMPLING AND ANALYTICAL TECHNIQUES

One composite vegetation sample and four soil 

samples two from the top 0-13 mm of soil and two 

within a depth of 25-152 mm were collected at 

most traverse stations. Soil samples were collected 

within a depth interval of 0-152 mm at stations 

where similar samples had been collected in 1961. 

The soil samples were put into paper envelopes designed for soil samples, and the plants were placed 

in #10 paper bags, which were sealed with tape. 

This procedure allowed the samples to be placed directly into the laboratory drier without transfer or 

additional handling. The samples were dried at 

30° C and ground to -80 mesh. The results are reported for air-dried samples.

End branches, including twigs and leaves, were 

collected from shrubs; herbs and grasses were cut 

off 50 mm above the ground, to avoid soil contamination. The plant samples were not washed, because 

their metal concentrations were compared with 

those of unwashed samples collected previously. 

Furthermore, the samples were of forage plants 

consumed by grazing animals rather than of corn, 

which is husked and shelled by man before being 

consumed. Plant samples collected by the EPA and
B4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

the Arizona Public Service Co. were also unwashed 

(EPA, written commun., 1975).

Two types of coal samples were collected: channel 

samples of the coal beds and plant-feed samples 

from the blend piles. Samples of bottom ash and 

fly ash were also obtained (collected by J. F. Fassett, U.S. Geological Survey). The coal and soil samples were dried, ground, and analyzed by several 

methods, including emission spectrographic, X-ray 

fluorescence, neutron activation, atomic absorption, 

and wet chemical. The coal samples were analyzed 

for trace elements, following procedures outlined 

by Swanson (1972, p. 9-19), and forms-of-sulfur 

determinations on the coal were made by the U.S. 

Bureau of Mines (Staff office of the Director of 

Coal Research, 1967). Analyses of the soil and plant 

samples were made following the procedures of 

Ward and others (1963; 1969). B, Ba, Be, Co, Cu, 

Mn, Ni, Pb, Sr, and V were determined by the sixstep emission-spectrographic method (Myers and 

others, 1961; Myers and Havens, 1970). By this 

method, the results are reported as the midpoints 

(1, 1.5, 2, 3, 5, 7) of geometric brackets within each 

order of magnitude. The precision of a reported

value is ±1 bracket at the 68-percent confidence 

level or ±2 brackets at the 95-percent confidence 

level. The reported midpoints are used in the tables 

and graphs.

A list of the analytical methods used and the 

limits of detection for each element are given in 

table 1. The analytical work was done in the laboratories of the U.S. Geological Survey under the direction of Claude Huffman, Jr., and Frederick N. 

Ward. The authors are grateful to them and to the 

chemists under their direction for providing the 

analyses used for the preparation of this report.

COAL AND COAL-COMBUSTION PRODUCTS

Upper Cretaceous coal, estimated at 720 or more 

billion metric tons, is widely distributed throughout 

the Southwest. The coal ranges in rank from subbituminous C to high-volatile C bituminous; it is 

low in sulfur, averaging about 0.6 percent S. The 

Four Corners Power Plant is using coal strip mined 

from six to eight beds in the Fruitland Formation 

of Cretaceous age (Fassett and Hinds, 1971) at the 

nearby Navajo mine. The major constituents of the 

ash of the coal used at the Four Corners Power

TABLE 1. Analytical methods used and lower limits of detection shown for selected elements, in parts per million

[Coal and plant samples reported in ash unless otherwise indicated. Leaders (___) indicate method not used for this material 1

Al ________

As

Be

B

Ba _ _ _ _

Ca

Cd ___ __

Co

Cr

Cu

F

Hg _________

Li ____ _ _

Fe _ __ _

Mg

Mo

Mn

Na

Ni

Pb ___ __

Sb _ __ _

Se

Sr

U

V

Zn

Emission spectrograph

Spectrophotometry

Emission spectrograph

__ _do __ ______ __ __ __ _ __ __.

____do : __ ______________________________

Atomic absorption

____do _____________________________________

Emission spectrograph

____do _____________________________________

Emission spectrograph

Specific ion electrode

Atomic absorption

Atomic absorption

Emission spectrograph

Emission spectrograph

Atomic absorption

Emission spectrograph

do

Flame photometer

Emission spectrograph

Emission spectrograph

__ do __ __ __ ___ ______________ _

Spectrophotometer

X-ray fluorescence

Emission spectrograph

Neutron activation

Atomic absorption

Coal

201 1.0

2

_ _ 50

3

1 100

\5

7

2

5

'BO

.01

5

20

100

7

2

100

10

20

\05

M

101 1

1 r\

10

Lower limits of detection

Soil

10

101

20

1.5

20

.2

3

1

1

.001

50

10

20

3

2

500

5

10

1

.1

5

7

.5

Plant

20

1 .25

2

50

3

50

.3

7

2

2

1 .6

1 .025

100

20

50

7

2

10

20

1

M

10

1 ^

.5

1 Dry weight.
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO B5

TABLE 2. Average major-oxide composition, in percent, of 

ash of coal used at Four Corners Power Plant (21 samples) and of coal used in the entire soutfnvestern United 

States (71 samples)

[Data from Swanson (1972)J

Oxide

Si03 __________ .

A1,O, __ _ __ __.

Na2 0 _____ _ __ .

K20 _________________

CaO ______

MgO _ __ _ __

P.O., -_-__-________ _.

Feo03 _ ___ _ _-

S03 _ _

Other

Total

Four Corners 

Power Plant

54 1

25.0

1.5

7

3.8

.8

.2

3.1

3.3

7.5

100.0

Southwestern 

United States

46.0

21.0

1.4

.5

8.5

1.7

.4

4.8

7.7

8.0

100.0

Plant are reported in table 2 as oxides. The compositions of all the southwest coals are remarkably 

similar, except for variations in the percent of ash 

(Swanson, 1972). The Four Corners Power Plant 

uses a blend of coal from two or more beds to maintain an average heat value of 5,000 kcal/kg and an 

average ash content of 21 percent.

The minor-element content of air-dried coal is 

compared with that of bottom ash, fly ash, and 

effluent in figure 5. Most heavy or inert elements are 

enriched in the bottom ash, as compared with the 

original coal, by the loss of combustible material. 

Considerable but unknown amounts of the volatile 

elements F, As, Se, and Hg are probably vaporized 

during combustion. The minor-element content of 

fly ash collected in the stack by the scrubbers and 

precipitators is also compared with the emitted particulate fraction being deposited on the soil and 

vegetation 1.6 km west of the plant. The latter material is more than 13 mm thick in the crowns of 

some of the shrubs. Although a certain amount of 

dilution by windblown silt has occurred, the volatile 

elements Hg and F are considerably more abundant 

in the windblown material than in the fly ash taken 

from the stack. The windborne material may be 

similarly enriched in As and Se, but no analytical 

data are available to verify this.

SOILS

Log-log graphs of the concentrations of Ba, B, Be, 

Ca, Pb, Ni, Mn, Cu, Hg, Se, Sr, V, Zn, and As in the 

top 12 mm of soils collected along three traverses 

from the power plant west (A-A'}, northwest 

(B-B'), and east (C-C") are shown in figure 6. 

Two soil samples were collected at each station (fig. 

1). Traverses A-A' and B-B' were across soils 

classified as badlands. Traverse C-C' was almost entirely across soils of the Werlow-Fruitland-Turley 

association, consisting of stratified alluvium of the 

San Juan River (Maker and others, 1973).

Contents of Ba, B, Be, Cu, Se, Sr, and As were 

uncommonly great in the area of ash disposal on 

traverse A-A' compared with their contents in average soils (Shacklette and others, 1971). As, Ca, Zn, 

and Cu were above average in soils along traverse 

A-A' only; Sr, B, and Se are above average for 

3.2-4.8 km on the A-A' and B-B' traverses; V, Ni, 

and Mn in all traverse samples, regardless of the 

rocks from which they are derived, are below the 

national average for soils (Shacklette and others, 

1971). At places on all three traverses, Be, B, Pb, 

and Hg appear to be more abundant than is normal, 

but sources of contamination other than the power 

plant are indicated for Pb and Hg. Lead contents 

are greater than normal in samples collected near 

highways. Although traverse A-A' paralleled only 

a dirt track, the track had heavy truck travel related to construction of new ash-pond facilities during the period of sampling.

Soils were collected in 1971 at 27 of the same 

sites sampled in 1961-62. Previously ground splits 

of the 1961-62 samples and newly ground 1971 samples were randomized and analyzed at the same 

time. The samples collected in 1961-62 contained 

slightly larger amounts of metal than those collected 

from the same sites in 1971. Experiments to determine the cause of this discrepancy show that the 

lower contents in the later samples are due to improved grinding practices. A comparison of samples 

collected at two sites from soil depths of 0-12 mm 

and 0-150 mm is given in table 3. No significant difference between samples collected at 0-150 mm and 

those collected from the top 12 mm can be discerned, except for a possible 1-step increase in lead 

in the top 12 mm.

VEGETATION

Splits of the early samples of vegetation were arranged in random sequence with samples from the 

later collection, and the entire lot of samples was 

analyzed as a group. The average quantities of elements in the 1971 samples are compared (fig. 7) 

with average quantities in 1961 samples. Certain 

minor elements in the vegetation are slightly more 

abundant in the 1971 samples than in the 1961 samples of the same species, which were collected at the 

same stations before construction of the power 

plant. An expectable decrease also occurs with increasing distance from the stacks.
B6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

10,000 r1000 -

Zr Mn V Li 

EXPLANATION

Effluent

Bottom ash 

Fly ash

? Not analyzed 

- Less than value

U As Se Mo Co Be Sb

ELEMENTS

0.01

Pb Cr Hg

FIGURE 5. Graph showing elemental components of coal and stack products of the Four Corners

Power Plant.
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO B7

TABLE 3. Inorganic composition of soils collected from two

stations

[Analyses by L. A. Bradley, H. G. Nieman, R. J. Turner, E. J. Fennelly, 

and J. A. Thomas, U.S. Geological Survey. N, not detected; L, below 

limit of detection. Leaders (--_) indicate not analyzed for those 

elements]

Station 21, 5.4 km NE. Station 25, 9 km E.

Element 1961 1971 1971 1961 1971 1971

0-150 

mm

0-150 

mm

top 

12 mm

0-150 

mm

0-150 

mm

top 

12 mm

Percent

Al .....

Mg ......

Fe .._._

Ca __ ..

Ti __ ..

K ._....

Na . __ .

Ba __ .

Mn _____

B _

Be ___ .

Co ___ .

Cr __ .

Cu _---..

La __ .

Mo ___ .

Ni __ .

Pb . _.

Sr ___ .

V ___ .

Y __ .

Zr ._._

Ga ....

Yb .._..

Hg _____

As _ ...

Zn _ ....

2

. . 7

. . .30

2

2

1000

300

. . 30

1

5

. _ 20

30

30

N

20

2000

70

15

300

20

2

10 

.5 

2 

3 

.20 

2 

3

Parts

2000 

300 

L 

1.5 

10

15 

20 

30

N 

7

20 

1000 

70 

30 

200

30 

3 

.02 

4 

51

7 

.5 

2 

2 

.15 

3 

2

per million

1000 

300 

L 

1.5 

10

15 

20 

50 

30

7

30 

700 

70 

30 

150

20 

3 

.02 

5 

53

10 

.5 

3 

1 

.20 

5 

1

700 

300

70 

2

7

50 

20 

70 

5 

15

20 

200 

100 

30 

200

20 

5

5 

2 

1 

.15 

.10 

3 

.7

1000 

200 

50 

1 

5

7 

5 

30 

N 

L

20 

100 

20 

10 

100

15 

1.5 

<-01 

3 

20

5 

.1 

1.5 

.15 

.1 

3 

1

1000 

200 

20

N 

7

7 

7 

30 

50 

L

30 

100 

20 

15 

100

15 

1.5 

L

3

17

Mercury contents of the early samples averaged 

0.41 ppm and those of the 1971 samples, only <0.025 

ppm. It can only be concluded that the early samples 

were highly contaminated with mercury during the 

10-year period of storage in a bunker formerly used 

for munitions storage at the Denver Federal Center. 

Although the percentage of mercury is slightly 

higher in the effluent than in the fly ash collected 

from the stacks of the Four Corners Power Plant 

(fig. 5), no mercury values greater than 0.025 ppm 

in dry weight were reported in the vegetation samples collected in 1971.

A later study of mercury in soils, vegetation, and 

water in the San Juan drainage basin was made to 

determine whether the power plant could be the 

source of mercury that had been detected in fish 

in Navajo Reservoir, 72.5 km northeast of the plant 

(Cannon and Swanson, unpub. data, 1972). The 

mercury in fish averaged slightly less than 0.5 ppm 

but was reported to be as high as 8.9 ppm in one 

chub (U.S. EPA, 1971). No evidence was found of 

a definable concentration of mercury in the environment that could be related to the power plant. Uncontaminated soils, in general, contained 0.05 ppm,

or less, all vegetation contained less than 0.025 ppm, 

and all water samples contained less than 0.5 /*g/L 

of Hg.

Our mercury study included an 80-km traverse 

from the power plant to the lake. The traverse was 

run along the alluvium of the San Juan River in 

order to avoid chemical variations in soils related 

to different geologic origins. Samples of sediments 

and plants were also collected from all drainages 

entering the lake. We expected to find mercury coming into the lake from the watershed to the north, 

where rocks of the San Juan Mountains might be a 

contributor of as much as 11.8 metric tons Hg per 

year, according to EPA estimates (1971). However, 

no increases attributable to this source were observed. Mercury contamination from gas pressure 

valves 54.7 km east of the power plant was considerably greater than that near the power plant itself. 

Because of this apparent association, additional 

samples were collected near gas wells, gas separators, gas pressure valves, and storage tanks; 

erratic mercury contamination in soils and plants 

of as much as 0.24 ppm in soils and 0.05 ppm in 

Artemisia tridentata (sage) was shown.

The elements that appear to have increased in 

concentration in the vegetation since the power plant 

was built are Cd, Ba, Cu, Pb, Sr, Fe, Mg, and Ti 

(fig. 7). The analyses, plant identifications, and distance and direction from power plant are given in 

table 4. However, no significant difference exists 

between the means of samples collected 0.6-1.7 km 

and 42-84 km from the power plant, for any element, determined on the basis of either a significance level of 0.01 or the application of the t test 

given by Natrella (1963). The lead concentration at 

station 186 is believed to be caused by highway pollution, because this station is adjacent to U.S. Highway 666. Mercury was not plotted, because it was 

generally below the limit of detection (0.025 ppm).

Because there was no record in the literature of 

fluorine concentrations in vegetation growing near 

power stations, 5 plants and 13 soils were analyzed 

for fluorine (table 5). In general, the top 13 mm of 

soil contained less fluorine than the soil at a depth 

of 25-152 mm. The highest fluorine concentrations 

occurred in alfalfa and grass growing on the alluvial 

flat of the San Juan River. No consistent relationship exists between the fluorine contents of soils and 

plants and their distance from the power plant. The 

higher concentrations of fluorine in the plants growing on alluvium reflect availability and may be related to the lower concentrations of calcium and
B8 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

1000 

500

O

_j 

2

IOO 

50

10

cc

LU 

Q.

100 

50

10

E

2 >

i 

FlGUR

of s 

alon 

Plar

phosj

r»a vor

1 1 Strontium

C I^s ^'(west) 

U.S. MEAN 250.0 >^J<^V \ -*

Aa^^—- X, >-\ o /VjC'(eosl) 

X'a^i>*fs /^5' (northwest) ^','-'' j

U.S. MEAN 80.0

4"^—— —— ^^-^^'(west) /<r --«

a—l^S' (northwest) 

Vanadium

Zinc (no C-C' analyses) 

U.S. MEAN 55.0 4^T^. /\A' (west)

CTjE-2 B (northwest)

„ Arsenic (no C-C' analyses) 

U.S. MEAN 5.0 ^^5J\ /j^'lwest)

^ //j^-a AB' (northwest)

yr- 8 v/

1 1 Power Plant i.ft 1ft IftO 

DISTANCE FROM POWER PLANT, IN KILOMETERS

E 6. — Graphs of elemental concentration in top 12 mm 

oils determined from sample pairs collected at stations 

g three traverses away from the Four Corners Power 

it.

)horus. These fluorine values may be com-

'WM+Vi •(•Vina/i in T-»1an + c< r>rklla^>'fa/l \\tr •f'Vi/i aoninv

O.I

Z

O 0.05

1

0.01 

0.005

0.001

cc

LU

a.

5.0

1.0 

0.5

E

2

O.I 

0.05

1 Mercury 

•<

/ , ;

U.S. MEAN 0.05 *\ f\ T'»- J / t \

/i\\ *' \ '' /'•' '^xX/V") 1 '

/ Vv * ' / c'(*°*t) / 4'1 X. _____ «'(north- V j 1 

c * (west)v v v v v west) v — v v

1

1 Selenium

- U.S. MEAN 0.45 ^vNSv/^ '- <v> / H

\lj\f\ 1 1 *' (northwest) ,*

—————— 

*' VH! i-'l'^N /""" *x^\ * ' ''\ —— / ——

v v v""'v

1

author from anomalous areas: for example, plants 

from the Gila Indian Reservation, Ariz., where the 

water is high in fluorine, contained 0.6-3.0 ppm F; 

plants from closed basins in Nevada and California 

contained 6-20 ppm; and plants growing on tailings 

of the Augusta gold mine, Colorado (5.7 percent F), 

contained 220-1,500 ppm. Fluorine accumulators, 

such as camellia, have been reported to contain as 

much as 3,060 ppm (Fleischer and Robinson, 1963).

SUMMARY AND CONCLUSIONS

Several conclusions can be drawn from this study. 

First, extra care must be taken to store and preserve unground splits of samples collected from uncontaminated areas in inert containers that cannot 

absorb volatile elements. These precautions are nee1.6 16 

DISTANCE FROM POWER PLANT, IN KILOMETERS

FIGURE 6. Continued.

essary because older samples will become increasingly important to studies of long-term changes in 

the environment.

Second, the present control of fly-ash emissions in 

the Four Corners plant reduces the contents of 

harmful metals in the effluent, except for fluorine 

and mercury, which are increased in the soil and 

vegetation near the plant. The levels of other elements present in the effluent drop off rapidly within 

a distance of a few kilometers; barium, strontium, 

beryllium, and lead are typical elements in this 

category. Both soils and vegetation in San Juan
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO B9

US. MEAN 20.0 A ACqr

U.S. MEAN 20.0

MongontM

U.S. MEAN 990.0

Copp«r

Po.tr Plant 1.6 16 160 

DISTANCE FROM POWER PLANT, IN KILOMETERS

FIGURE 6. Continued.

County are very deficient in these and most other 

essential elements. In an area of such deficiency, 

the addition of some elements from the effluent may 

actually be beneficial; plants do not require the elements most harmful to man and are therefore not 

concentrating them in greater quantities than occur 

in the soil. Levels of harmful metals in vegetation 

are very low or even below the limits of detection, 

except for lead, which appears to have increased 

throughout the area since 1961 and is highest near 

highways.

/ /J

i^^ /.i.\ ^i 

" """ " * "" "

Beryllium

U S MEAN 1.0

»'(w«5t)

Calciu

1.6 16 

DISTANCE FROM POWER PLANT. IN KILOMETERS

FIGURE 6. Continued.

Third, there is no evidence that mercury, which 

had been detected in Navajo Lake, is coming from 

the power plant or from geologic sources in the 

watershed; the nearby gas field is a more likely 

source.
BIO SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 4. Composition of vegetation collected at various

LAnalyses by T. F. Harms, C. S. E. Panp, and L. D. Forshey, U.S. Geological 

leaders (-__) indicate no sample available; =, approximately equal to. Means

Distance 

(km) and 

direction 

frompower gpecies

2.9 EN'E Juncus balticus _

3.2 W Atriplex nuttali _ .

9.7 NW Corn ........ .. ._ . .

9.7 NE Sporobolus airoides

14.5 NE Atriplex nuttali __ . ...

14.5 NE Calamagrostis inexpansa 

16.1 NW Alfalfa . _

Mean 1-20 km

23 ENE Artemisia tridentata -__.___ 

22.5 NE Gutiorrezia lucida

24.1, E Chrysothamnus nauseosus __ 

Chrysothamnus nauseosus __ 

27.4 NW Atriplex corruqata

31.5 SE Ephedra torreyana

31.5 W Atriplex confertifolia

38.6 SE Eriogonum leptophylum ____ 

40.2 SE Atriplex powelli . _ .

Mean 21-40 km

44.1 SSE Betula erecta ...

46.8 SW Atriplex confertifolia ______

48.3 SW Atriplex confertifolia ______

49.9 ENE Artemisia tridentata __ _ __

Atriplex confertifolia ______ 

54.7 E Alfalfa _ _ _. _ _ _ __

____do __ ______ __ __ _ _.

55.1 ENE Artemisia tridentata _______

Mean 41-80 km

Station

Lab

No. 1

411 415911 

303 415658 

412B 415915 

412A 415908

305A 415665 

305B 415653 

413 415914 

70 415738

414 415912 

21 415654 

415 415916 

182 415725

416 

22 

22 

25 

25 

186 

186

65 

65 

56 

56

57 

57

67 

67 

417 

62 

16 

16

11 

11 

44 

44 

43 

43 

28

47 

47 

74 

74 

418 

419

415919 

415729) 

415735J 

415726) 

415734f 

415662) 

415659}

415731] 

415736C 

415657) 

415666} 

415667) 

416661}

415733) 

415739} 

415917 

415732 

415660) 

415665f

415740) 

415730} 

415664) 

415652f 

415656) 

415669} 

415728

415668) 

415663 f 

415737) 

415727f 

415910 

415918

Ash, in 

percent

1961

_-

___

---

12 "

6 

8.2 

29

13 

30 

37

6.8

26

19

26 

36 

23

28 

15

26

1971

11 

33

Q O

11

30 

29

8.9

2.9 

9 9

26 

10 

9.2

16

Q *>

7.2 

7.1 

27

12

17 

20

5.5 

9 1

6.5 

28

14

24 

13

16 

4.7

6

7.4

9.1 

9 2

11

1961

---

<0~25

< .25 

< .25 

< .25

< .25 

< .25 

.25

< .25

.25

<0.25

<0.25 

.25 

< .25

< .25 

.25

<0.25

As

1971

.5

< .25 

< .25

< .25

.5 

< .25

<0.25

.25 

< .25 

.5

< .25 

.25 

< .25

< .25

< .25 

< .25

<0.25

<0.25 

< .25

< .25 

< .25

< .25 

.25

<0.25

Chemica

1961

____

 -

o~r~

.2 

.3 

< .025

.3

.8

.7

.4

< .025

0.44

<0.025 

.3 

1

.7 

.3

0.46

1 analyses, in parts per million

Hg

1971

<0.025 

< .025 

< .025 

< .025

< .025 

.025 

< .025 

< .025

< .025 

< .025 

< .025 

< .025

<0.025

<0.025 

< .025

< .025 

< .025

.025 

< .025 

< .025

< .025

< .025 

< .025

< .025

<0.025

<0.025 

< .025

< .025 

< .025

< .025

.025

< .025 

< .025

<0.025

Cd Zn

1961 1971 1961 1971

....

---

.048

.13 

.082 

.2

.065 

.09 

.11

.136

.08

0.11

0.1 

< -1

.6

.25 

.06

0.41

.13

.10 

.09

.01

.08

.04

0.07

.11 

.71 

.19

.08 

.08 

.12

.14

.08 

.08

0.18

0.17 

.08

.18 

.30

.56 

.03

0.22

--

27

40 

57 

20

17 

9 

11

46

29

29

21 

13 

42

20 

15

23

26

22 

22

38 

?5

18

25

14 

78 

13

9

8 

8

31

21 

29

23

48 

10

13 

38

110 

15

39

Se

1961

____

----

.7

.3 

.2 

5.04

.3 

.4 

.1

.1

.2

0.8

0.05 

.1 

.075

.6 

.3

0.22

1971

.2

1.5 

1.5

.05 

.3

.1

0.6

.3 

.1 

.5

.1

.7 

.4

.075

1.5 

5.

1.0

0.075 

.2

.1 

.075

.4 

.075

0.15

Spectrographic 

analysis, 

in parts peimillion

Mn

1961 1971

--

--

--

19

30 

80 

58

65 

30

74

48

40

53

78 

54 

115

84 

30

72

16 

100 

27 

350

60 

58 

28 

9

30 

78 

70 

28

88

28 

36

22 

80

36 

34 

40

28

26 

20

8.4

33

73

65

80 

14

200

22

27 

64

68

1 Where two laboratory numbers are given, top is 1961, bottom is 1971.
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO Bll

distances from the Four Corners Power Plant, shown in dry weight

Survey. >, greater than value given; <, less than detection limit; N, not detected; 

computed using 0.5 of the less-than values and two times greater-than values |

Spectrographic j

B Ba

1961 1971 1961 1971

84

30 

40 

9

13 

21 

55

48 

18

32

39 

36

70

84 

45

55

16 

50 

13 

17

45

44 

13 

2.0 __

15 

25 

14 

65 12

27

14 

36

35

27

12 

17 

30

16

13 

45

28

25

36 

20

24 

14

42

52

14 

18

28

42 

12 

29

130 

45 

74

14

78

53

260 

108 

35

140 

150

138

33 

500 

27 

16

150 

200

27

.87

30

182

7 

28

100

28 

100

21 

81

120 

25 

60

48

26 

65

55

53

120 

65

48 

.7

420

22

14 

4.6

92

Cr

1961

< 1.1

N

----

____

.6

.6

1.2 

5.8

2 

9. 

11

68

13

5.4

7.8 

7.2 

3.5

4.2 

2.2

5

1971

0.55 

6.5 

.62

< -2

2.1

.03 

1.5

3.9 

.2

.64

1.6

1.4 

1.4

1.0 

5.4

1.2 

1.7 

2

1.1 

1.3

5.6

2.1

2.4 

.65

2.4 

.47

4.2

.37

1.4

2.8

1.8

analysis, in parts per million Continued

Cu Mo

1961 1971 1961 1971

_._

 

___

8.4

9 

16

5.8

4 

6 

5.7

20

7.8

9.3

5.2 

3.6 

4.6

56 

22

18

7.7 

10 

4 5

5 5

9

8.7

5.8

6 q

13

7 0

9.2

7.8

14 

11

35 

5.4

3.6 

6 

6

16

86

8.4

10.7

12 

3.9

4.8 

14

4.2

7.4

14

fi 4

8.3

__ < 0.8

____ .62

.___ < 2.

.58 

69

 . < 1.6

6.4 14

=1.8

___^ 0.65

.9 .72 

1.6 1.0 

<2. < 1.9

< .9 < .8 

<2 < .9 

<2.5 < 1.4

1.4 .82 

 _ < .6

____ 1.0

.78 < 2

=1. =0.68

<2 < 1.7 

<2.6 < 1.3

<1.6 < 1.2 

.33

2.8 < .4

<1. .74 

____ .91

=1.3 =0.6

Pb

1961

<2

____

3.6

3

2.5

8.7

2.6

<7 

2

<5

=3.5

<5 

<5

8.4

=3.7

1971

< 2

2.5

< .6

<" 2.0

1.84

=3.

6.4

11

7

3.6 

< 1.2 

4.

3.8 

6.0

5.6

5.8

< 4.8 

< 2.6

4.6 

1.4

< 1.2

2.2 

14

=4.1

Si1961

____

____

360

120 

410 

145

910 

450

370

340

130

360

1300 

100 

115

840 

225

515

1971

77 

100 

27

77

150 

145 

27 

5.J

30 

250 

30 

180

92

140

140

355 

400

600 

250 

300

165

13U 

320

130

280

720 

90

460 

140

420

520 '

64 

92

310

V

1961 1971

____

5 __ _

 -

1.2 

1.2

8.7

4. 

<4.5 

5.5

1.4

7.8

=4.

5.2 

<5.4 

<3.5

5.6 

4.5

=3.8

10.

4.5

Q rr

1 S

< .45 

2.0

13 

< 1.5

< 1.4

=3.7

5.0 

1.4 

5.4

2.4 

< 2.5 

< 3.

2.7

7.8

=3.7

< 3.6 

1.9 

< 2.4

4.2 

< 1.1

1 S

2.3

Spectrog

Fe

1961 1971

0.02

.045

raphic

Mg

1961 1971

.0077

____

.000 

.04 

.14

.13 

.09

.18

.05

.26

0.11

C.13 

.18 

.11

.28 

.10

0.16

.15

.004

.007

.018

0.13

0.09

.14

.07 

.135

.08 

.05 

.06

.04 

.06

.28

0.10

0.17 

.04

.08 

.02

.20 

.04

09

0.11

---

.18 

.25

.87

.26 

.9

1.8

.2

.39

0.6

0.26 

.54 

.35

.42 

.15

0.34

0.33

1.0

.09

.OS

.45

.43

09

.145

.1

.52

.1

.27

0.30

0.14

.14 

.14

.54

.18 

.5 

.6

.16 

.14

.45

.42

0.32

0.36 

.26

.32 

.33

.56

.11

09

0.26

analysis, in percent

K

1961 1971

_ _ 0.77

2.3

___ > .89

3.3

2.0

> .89

_____ > .29

_____ 1.8

> .92

=1.1

_____ >0.9

> .6 .5 

> .8 > .7

.17 1.9

.9 .84 

3. 1.7 

2.6 >2.

> .68 > .55 

>-9

__.__ > .0

>2.6 2.8

=2.0 =1.7

>2.6 2.6 

2.5 1.3

.8 .8 

_____ > .47

>2.8 1.4

1.5 > .74 

> .91

__.-. > .92

=3.1 =1.5

P

1961 1971

_____

.12

.12 

.08 

< .2

.09 

< .2 

< .26

.2

< .18

=0.11

<0.16 

<.25 

< .16

.23

.1

=0.16

0.11 

< .23 

.06 

.055

< -21 

< -21 

.06 

.3

< .05 

< .18 

.07 

.09

=0.10

0.09 

.07

.07 

< -2

< .02 

< .12 

< .14

.11

.06 

.06

< .2

=0.16

0.26 

.007

< -11 

.09

< .04

.15

.14 

.06

=0.13
B12 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

10,000

1000

X 

UJ

V

a: 

o

cc

LJ

o_

o: 

< 

o_

100

10

O.I

O.QI

EXPLANATION 

\\J Average sample values 1961 • '• 0

H Average sample values 1971 

— Average shrub values

Mg Fe Mn Zn Sr B Ba Ti Cu Pb V Cr As Cd Hg

ELEMENTS

FIGURE 7. Graph showing concentrations of some elements in San Juan County vegetation 

collected in 1961 and 1971 compared with concentrations in the average shrub.

TABLE 5. Fluorine analyses of soils and vegetation in relationship to the Four Corners Power Plant, shown in parts per

million

[Analysis by T. F. Harms and F. N. Ward. Leaders (.._) indicate no sample]

direction from plant

0.8 W. __ _ __

1.6 W. _

3.2 NW. _ _

6.4 NW. _____

8.9 E.1 _

14.5 E.1 __ __ __ _

16.1 NW.1 __ __

Plant

Genus and species (common name)

A triplex nuttali (saltbush)

Lab. No.

415658

415653

414912

415916

415741

F, in 

dry weight

3.0

7.0

25.0

7.0

20.0

Lab. No.

153500

153493

153496

154644

415966

415969 

415972 

415967 

415971

415974 

415977 

415981 

153479

Soil

F, in 

dry weight

390

300

340

90

280

270 

290 

340 

300

330 

290 

340 

510

Depth 

( millimeters )

15

15

15

15

15

25-150 

15 

25-150 

15

25-150 

15 

25-150 

15

1 Plant growing in alluvium along San Juan River; both plant and alluvium sampled.
CONTRIBUTIONS OF ELEMENTS BY THE FOUR CORNERS POWER PLANT, NEW MEXICO B13

With the installation of equipment for further 

treatment of the fly ash, much of which had already 

been installed (as of 1972), the Four Corners Power 

Plant effluent may be considered as not detrimental, 

except for (1) a decrease in visibility and, possibly, 

(2) the effects of S02 , which were not investigated 

in this study. However, in areas where prior high 

levels of metals occur in the geologic substrate and 

related biosphere, increments from industrial plants 

should be carefully monitored.

REFERENCES CITED

Averitt, P., and others, 1972, Coal resources and reserves of 

the southwestern United States, in Coal Resources Work 

Group Report: U.S. Department of the Interior, Southwest Energy Study, Appendix J, pt. 1, p. 1-74.

Cannon, H. L., and Anderson, B. M., 1972, Trace element 

content of the Four Corners Power Plant, in Coal Resources WT ork Group Report: U.S. Department of the 

Interior, Southwest Energy Study, Appendix J, pt. Ill, 

p. 1-44.

Fassett, J. E., and Hinds, J. S., 1971, Geology and fuel resources of the Fruitland Formation and Kirtland Shale 

of the San Juan Basin, New Mexico and Colorado: U.S. 

Geological Survey Professional Paper 676, 76 p.

Fleischer, Michael, and Robinson, W. 0., 1963, Some problems of the geochemistry of fluorine, in Studies in 

analytical geochemistry: Royal Society of Canada Special 

Publication 6, University of Toronto Press and Royal 

Society of Canada, p. 58-75.

Maker, H. J., Keetch, C. W., and Anderson, J. U., 1973, Soil 

associations and land classification for irrigation, San 

Juan County: New Mexico University Agricultural Experiment Station Research Report 257, 44 p.

Myers, A. T., and Havens, R. G., 1970, Spectrochemistry applied to g-eology and geochemistry by the U. S. Geological Survey in the Rocky Mountain Region, in 2nd Seminar on Geochemical Prospecting Methods and Techniques, 

Proceedings: U.N. ECAFE Mineral Resources Development Series 38, p. 286-291.

Myers, A. T., Havens, R. G., and Dunton, P. J., 1961, A spectrochemical method for the semiquantitative analysis of 

rocks, minerals, and ores: U.S. Geological Survey Bulletin 1084-1, p. 207-229.

Natrella, M. G., 1963, Experimental statistics: U.S. National 

Bureau of Standards Handbook 91, p. 3-26 to 3-30.

Shacklette, H. T., Hamilton, J. C., Boerngen, J. G., and 

Bowles, J. M., 1971, Elemental composition of surficial 

materials in the conterminous United States: U.S. Geological Survey Professional Paper 574-D, 71 p.

Staff Office of the Director of Coal Research, 1967, Methods 

of analyzing and testing coal and coke: U.S. Bureau of 

Mines Bulletin 638, 85 p.

Swanson, V. E., 1972, Composition and trace element content of coal and power plant ash, in Coal Resources 

Work Group Report: U.S. Department of the Interior, 

Southwest Energy Study, Appendix J, pt. II, p. 1-61.

U.S. Environmental Protection Agency, 1971, A preliminary 

assessment of mercury pollution in Navajo Reservoir, 

Colo.-N. Mex.: Denver, Colo., Office of Enforcement, 

Division of Field Investigations. Pages unknown.

Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, 

Analytical methods used in geochemical exploration by 

the U.S. Geological Survey: U.S. Geological Survey Bulletin 1152, 100 p.

Ward, F. N., Nakagawa, H. M., Harms, T. F., and VanSickle, G. H., 1969, Atomic-absorption methods of analysis useful in geochemical exploration: U.S. Geological 

Survey Bulletin 1289, 45 p.

Radioelement Concentrations and 

Preliminary Radiometric Ages of 

Rocks of the Kigluaik Mountains, 

Seward Peninsula, Alaska

By CARL M. BUNKER, CARL E. HEDGE, and C. L. SAINSBURY

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-G

A long-lived thorium-rich province 

indicated by isotopic analyses

CONTENTS

Page

Abstract _______________________________________________ Cl

Introduction _______________________________________ 1

Acknowledgments ______________________________________ 2

General geology ________________________________________ 2

Method of analysis ____________________________________ 3

Radiometric ages _____________________________________________ 5

Radioelement distribution _____________________________ 7

References cited ____________________________________________________ 11

ILLUSTRATIONS

Page

FIGURE 1. Index map of Seward Peninsula, Alaska, showing area of detailed study and sample localities outside the

study area ______________________________________________________ C2

2. Generalized geologic map, showing sample localities, Kigluaik Mountains area, Alaska and a list of sample localities and their field numbers _______________________________________________ __ 4

3. Isochron diagram of Rb-Sr data for whole-rock paragneiss (Kigluaik Group) samples _______ _ 6

4. Isochron diagram of Rb-Sr data for whole^rock orthogneiss samples _____________________________ 7

5. Radioelement concentrations related to geology, Kigluaik Mountains area, Alaska ______________ 9

6. Log-log plots of concentrations of radioelements in rocks of the Kigluaik Mountains, Alaska _______ 10

TABLES

Page

TABLE 1. Rb-Sr analytical data _______________________________________________ C5

2. Concentrations and ratios of radioelements, Kigluaik Mountains, Alaska ______________________ 8

3. Averages of radioelement contents and ratios in rocks of the Kigluaik Mountains, Alaska, and summary

of published averages for igneous rocks _______________________________________________ 10

III

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

RADIOELEMENT CONCENTRATIONS AND PRELIMINARY RADIOMETRIC 

AGES OF ROCKS OF THE KIGLUAIK MOUNTAINS, SEWARD PENINSULA,

ALASKA

By CARL M. BUNKER, CARL E. HEDGE, and C. L.

ABSTRACT

A sequence of old metamorphic rocks including the 

Kigluaik and Nome Groups is exposed in the Kigluaik Mountains of the Seward Peninsula. The high-grade metasedimentary rocks give a whole-rock Rb-Sr age of 735 million 

years. This late Precambrian age is believed to be the time 

of metamorphism. Orthogneisses, intrusive into the metasedimentary rocks, are probably also Precambrian in age, but 

many samples have had the evidence for their ages disturbed 

by Cretaceous intrusions and thrusting.

Samples of Precambrian metagabbro are low in radioelemenbs (U, Th, and K) typical of basaltic rocks. The Precambrian metasedimentary rocks have normal radioelement 

concentrations, but both the Precambrian Orthogneisses and 

the Cretaceous granitic rocks are uncommonly rich in 

thorium.

INTRODUCTION

The existence of rocks of Precambrian age on the 

Seward Peninsula, Alaska, has been a matter of 

lively argument. The rocks discussed herein were 

suspected by Moffit (1913) to be of Precambrian (?) 

age but were subsequently shown on later maps to 

be of Paleozoic (?) age (Hummel, 1962; Patton, 

1967). After several years of mapping on the Seward Peninsula, Sainsbury (1969a) demonstrated 

that fossiliferous limestones of Early Ordovician 

age on the western Seward Peninsula were underlain by an older, unfossiliferous limestone that 

graded downward into slates and phyllites of possible Precambrian age but that, on the basis of stratigraphic evidence, could be proved only to be preOrdovician. As mapping progressed eastward into 

the area discussed in this report, the determination 

that the age of the rocks is Precambrian seemed almost certain. However, the widespread thrusting,

1 AirSamplex Corporation, Indian Hills, Colo.

with both regional dynamic metamorphism and 

younger thermal metamorphism impressed upon the 

thrust plates, made dating of the rocks of the Seward Peninsula by stratigraphic position and metamorphic rank impossible. Nevertheless, the stratigraphic evidence gathered in the western Seward 

Peninsula was sufficient to warrant an assignment 

of Precambrian age to most of the rocks older than 

the Lower Ordovician limestones.

This study was initiated in an attempt to verify 

the assignment of a Precambrian age to certain 

units and to determine the radioelement characteristics of various suites of metamorphosed rocks. Results of the study are that a Precambrian age has 

been verified for gneisses in the Kigluaik Mountains 

and that certain units have radioelement "signatures," which can be used for making correlations.

Although the preliminary work was published 

several years ago (Sainsbury, Coleman, and Kachadoorian, 1970; Sainsbury, Hedge, and Bunker, 

1970), recent maps of the Seward Peninsula still 

show the bulk of the rocks to be of Paleozoic age 

(Clark and others, 1972). Since the initial work, 

more collections of rocks have been dated and analyzed for radioelement content. Because such data 

have not been published for Alaskan rocks, it was 

considered important to present the data that have 

been collected so that other workers will have a 

basis for comparing Alaskan rocks with those studied elsewhere.

The Kigluaik Mountains were chosen for this 

study for the following reasons: (1) A large variety 

of rock types ranging in age from Precambrian to 

Cretaceous are well exposed in a relatively small 

area; elsewhere in the Seward Peninsula, much of 

the land surface is covered by tundra, outcrops of

Cl
C2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

similar rocks are isolated, and stratigraphic relationships are less evident. (2) Rocks exposed in the 

Kigluaik Mountains are less weathered than are 

other rocks that crop out in much of the Seward 

Peninsula; thin layers of visible alteration on the 

samples were common, but these were removed prior 

to analyses.

The Kigluaik Mountains are about 24 km wide 

(north to south) and about 72 km long within the 

area of 64°45' to 65°05' N. latitude and 164°45' to 

166°15' W. longitude (fig. 1). The center of the 

mountain range is about 48 km north of Nome. 

Much of the northern part of the range is delineated 

by an escarpment along the Kigluaik fault; part of 

the southern boundary generally coincides with a 

group of lesser faults. This area is included in parts 

of the Nome and Teller 1:250,000 Alaska Topographic Series maps.

ACKNOWLEDGMENTS

The geologic mapping of the region under study 

was the responsibility of Sainsbury, who was 

assisted ably by Travis Hudson, Reuben Kacha168 165° 162°

SEWARD PENINSULA

70AH-616 IBENDELEBEN 

1 MOUNTAINS

70AH-617

)p>^OT KIGLUAIK 

^a^P^MOUNTAI REPORT 

AREA

50

I

100 150 KILOMETERS 

I______|

FIGURE 1. Index map of Seward Peninsula, Alaska, showing area of detailed study and sample localities outside 

the study area.

doorian, T. W. Smith, Thomas R. Richards, Rodney 

Ewing, and William R. Marsh at various times. Assignment of units and ages is the responsibility of 

Sainsbury. The rocks discussed herein were analyzed for radioelements by Bunker, who has guided 

the writing of the report; Charles A. Bush assisted 

with the analytical work. The age dating of the 

rocks by rubidium-strontium methods was done by 

Hedge, assisted by William T. Henderson, Robert 

A. Hildreth, and Willis P. Doering. Each of the 

authors of this report thereby assumes responsibility 

for his part of the report.

GENERAL GEOLOGY

The general geology for that part of the area 

within the Teller 1:250,000 quadrangle has been 

described by Sainsbury (1972). For the general 

area of the Seward Peninsula, the geology was 

summarized by Sainsbury (1975) and by Sainsbury, Coleman, and Kachadoorian (1970), in a report in which arguments for the Precambrian age 

of the rocks were presented. Short texts in which 

the rock units are described in some detail were 

prepared by Sainsbury and his coworkers to accompany numerous published geologic maps (Sainsbury, 

1969a, 1969b; Sainsbury, Kachadoorian, Hudson, 

and others, 1969; Sainsbury, Kachadoorian, and 

Smith, 1970; Sainsbury, 1972; Sainsbury, Hummel, 

and Hudson, 1972; Sainsbury, Smith, and Kachadoorian, 1972; and Sainsbury, 1974).

Briefly stated, the Seward Peninsula consists of 

a great number of thrust plates of Paleozoic carbonate rocks intimately intermixed tectonically with 

Precambrian rocks. Present are argillaceous and 

dolomitic limestone, the slate of the York region, 

and several types of chloritic schists, feldspathicchloritic schists, and high-rank gneisses and schists 

predominantly of leucocratic composition. Whether 

the chloritic schists are all old volcanic rocks that 

were intercalated in the slate of the York region or 

whether some are younger mafic rocks possibly intruded during the thrusting is as yet unsettled. All 

of the Paleozoic rocks on the western part of the 

Seward Peninsula that have been dated by fossils 

are carbonate rocks of Ordovician, Silurian, Devonian, and Mississippian(?) ages. Unfossiliferous 

rocks of noncarbonate composition cannot be assigned to the Paleozoic, and furthermore, whenever 

the slate of the York region is overlain by massive 

carbonate rocks without the intervening argillaceous 

and dolomitic limestone, the two units are separated 

by either a thrust fault or an unconformity.
RADIOELEMENT CONCENTRATIONS, RADIOMETRIC AGES, KIGLUAIK MOUNTAINS, ALASKA C3

Along the axes of the Kigluaik and Bendeleben 

Mountains, which trend eastward across the Seward 

Peninsula, high-rank gneisses, semigneisses, and 

schists are exposed, and these are intruded t»y numerous granitic intrusive rocks mostly of Cretaceous age. However, some gneissic intrusives of 

granitic composition have been mapped, and these 

may be of Precambrian age. Because the gneisses 

and intrusive rocks of the Kigluaik Mountains have 

been studied more extensively, the initial work of 

age dating and determining radioelement contents 

has been concentrated in this area, but data from 

elsewhere on the Seward Peninsula are included.

The complications introduced as a consequence of 

the intense tectonic deformation of the thrust belt 

covering the Seward Peninsula, named the A. J. 

Collier thrust belt to honor a pioneer worker of the 

Seward Peninsula (Sainsbury, 1969b), are immense. 

Large-scale migration of material took place during 

thrusting, and the thermal metamorphism imprinted 

upon the dynamically metamorphosed rocks has 

been widespread. Nevertheless, the data that have 

been gathered substantially support the geologic 

interpretations made over the years. More importantly, the Precambrian age of most of the metamorphic rocks of noncarbonate composition is clearly established. Only by application of whole-rock RbSr age dating was the correct age established, because dating of the high-rank schist by K-Ar 

methods yielded Cretaceous dates similar to the ages 

of the intrusive rocks.

The geology of the Kigluaik Mountains and the 

location of samples analyzed in this study are shown 

in figure 2. Three samples of orthogneiss, which 

were included in the Rb-Sr dating, are outside of 

this map area and are shown in figure 1.

The oldest rocks are the paragneisses of the 

Kigluaik Group. These rocks are well exposed in the 

Kigluaik Mountains. The dominant lithologies of the 

Kigluaik Group are plagioclase-orthoclase-biotitehornblende gneiss and gneissic marble. These paragneisses are intruded by orthogneisses ranging in 

composition from granite to quartz monzonite.

Two major lithologic units, which either may be 

the unmetamorphosed equivalents of part of the 

paragneisses herein discussed or may be somewhat 

younger in age, are found in the Kigulaik Mountains and nearby areas discussed in this report. 

These were named the Nome Group and the Kuzitrin Series by Moffit (1913) and by Brooks, Richardson, and Collier (1901), respectively. In his 

latest publication, written after a detailed study of 

the metamorphic rocks in the Kigluaik Mountains

and elsewhere on the Seward Peninsula, Sainsbury 

(1975, p. 8-19) presented evidence that the highrank gneisses of the Kigluaik Mountains are transitional, at least in part, into graphitic slates and 

siltites of the Kuzitrin Series, which he includes 

with the slate of the York region. He further 

concluded that the rocks of the Nome Group as 

originally defined by Brooks, Richardson, and Collier 

(1901) included chloritic schists, probably derived 

from volcanic material originally included in the 

slate of the York region, as well as thrust slices of 

Paleozoic carbonate rocks and younger metagabbroic rocks of uncertain age. Thus, the Nome Group 

rocks may be a subunit within the slate of the York 

region, but only detailed study will solve the 

problem.

No rocks of proved Paleozoic age are found in 

the Kigluaik Mountains, but thick carbonates containing relict fossils occur immediately south and 

west of the range. These were grouped by earlier 

workers as part of the Nome Group, but the known 

existence of relict fossils and the lithologic resemblance to other carbonate rocks of Paleozoic age that 

occur nearby are considered by Sainsbury to be sufficient evidence to assign these carbonate rocks to 

the Paleozoic.

The rocks forming the core of the Kigluaik Mountains are intruded by stocks, bosses, and batholiths 

of probable Cretaceous age. In broad outline, the 

high-rank gneisses herein discussed tend to form 

mantles around these intrusives, as they do elsewhere on the Seward Peninsula (Sainsbury, 1974, 

1975).

METHOD OF ANALYSIS

Rubidium and strontium concentrations were determined either by X-ray fluorescence or by isotopedilution techniques. Concentrations in all of the 

samples with extreme Rb-Sr ratios were measured 

by isotope dilution. The Rb-Sr ratios have a precision of ±3 percent. Sr87 /SrSG were measured on a 

separate unspiked run; they were normalized to correspond to an SrSG /SrS8 of 0.1194 and have a precision of ±0.0005.

Radioelement (K, RaeU (radium-equivalent uranium) and Th) contents of the samples were measured by gamma-ray spectrometry. Basic operational procedures, calibration techniques, and sample 

preparation were described by Bunker and Bush 

(1966, 1967). Approximately 600 g of the material 

were sealed in plastic containers 15 cm in diameter. 

The containers were placed on a sodium iodide 

crystal, 12.5 cm in diameter and 10 cm thick. The
C4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

166°30' 166°00' 165°30r 165°00'

65

V:V;'';:';:r -'; Contact-Dashed where approximately located, 

gradational, or inferred; queried where doubtfu

Quaternary glacial deposits-Includes 

moraine and outwash material

Orthogneiss-Derived from granites to quartz

'p€?n>' Nome Group-Chloritic schists, metavolcanics, 

and thick marbles and micaceous marble 

schists; subordinate graphitic schists

Kigluaik Group-Includes an upper unit of calcsilicate rocks with numerous schistose 

marbles, a middle unit of marble gneiss, 

and a lower unit of paragneiss with 

calc-silicate rocks

Cretaceous igneous complex of Kigluaik 

Mountains-Includes rocks ranging 

from granite to diorite, and numerous 

roof pendants of Kigluaik Group

Precambrian 

Argillaceous limestone

Gabbro-lncludes gabbro and other 

highly altered mafic rocks

pGs-Slate, phyllite. and quartz siltite;

minor black limestone 

pGsb-Graphite-bearing biotite schist,

slate and calc-silicate rocks.

Believed to be metamorphosed

equivalent of pGs, but may be

an older unit

FIGURE 2. A, Generalized geologic map showing sample localities, Kigluaik Mountains area, Alaska.

gamma radiation penetrating the crystal was sorted 

according to energy by the associated electronic devices, and the resulting spectra were stored in a 

100-channel memory. The spectra were interpreted 

with the aid of a linear-least-squares computer

method that matches the spectrum from a sample 

to a library of radioelement standards; the computer method for determining concentrations is a 

modification of a program written by Schonfeld 

(1966). Standards used to reduce the data include
RADIOELEMENT CONCENTRATIONS, RADIOMETRIC AGES, KIGLUAIK MOUNTAINS, ALASKA C5

Sample Field Sample Field 

locality number locality number

1 70ACH-17 21 67ATS-159 

2 70ACH-18 22 67ATS-80 

3 70ACH-21 23 67ATS-156 

4 70ACH-26 24 67ATS-156A 

5 70ACH-15 25 67ATS-163

6 70ACH-16 26 67ATS-195 

7 67ATS-132 27 67ATS-223 

8 70ACH-27 28 67AKd-190 

9 70ACH-24 29 67ATS-161 

10 68ASn-282 30 67ATS-197A

11 68ASn-282A 31 67ATS-222 

12 67ATS-184-1 32 67AKd-212 

13 67ATS-184-2 33 70AcH-23 

14 68ASn-30lB 34 67ASn-3lA 

15 70ACH-28 35 67ATS-184A

16 70ACH-14 36 68ASn-280 

17 70ACH-20 37 67ASn-124 

18 70ACH-19 

19 70ACH-1 

20 70ACH-2

B

FIGURE 2. B, List of sample localities shown on A and their 

field numbers.

the USGS standard rocks, New Brunswick Laboratories standards, and several samples for which 

uranium and thorium concentrations had been determined by isotope dilution and mass or alpha 

spectrometry. 

Uranium contents were measured indirectly by 

measuring the Ra226 daughters (Bi21t and Pb211 ) to 

obtain RaeU values. Isotopic equilibrium between 

these daughters and Ra226 was reached by allowing 

the sealed sample containers to sit for at least 21 

days prior to the analyses. (Radium-equivalent 

uranium is the amount of uranium required for 

secular isotopic equilibrium with the Ra226 and its 

daughters measured in a sample. Unless otherwise 

stated, all uranium concentrations referred to in this 

paper are radium-equivalent values.) 

Although thorium is also measured from daughter 

products (Bi212 , Pb212 , and T120S ), isotopic disequilibrium is improbable because of the short half -lives 

of the daughter products of Th232 . Therefore, the 

daughter products measured are considered to be a 

direct measurement of thorium. Potassium is determined from the K40 constituent, which is radioactive and directly proportional to the total 

potassium. 

All the radioelement data reported in this paper 

are based on replicate analyses. The coefficient of

variation lor the accuracy 01 tnese data, wnen compared to isotope-dilution and flame-photometry analyses, is about ±2 percent for RaeU and Th and 

about ±1 percent for K. These percentages are in 

addition to minimum standard deviations of about 

0.06 ppm for RaeU and Th and 0.03 for K.

RADIOMETRIC AGES

Seven whole-rock samples of paragneiss from the 

Kigluaik Group were dated by the Rb-Sr method. 

Samples were obtained from both the uppermost 

and lowermost accessible portions of the unit. Analytical data for the paragneiss samples are given in 

table 1 and are plotted on an isochron diagram in 

figure 3. Also dated from the Kigluaik Group were 

one sample of biotite separated from the paragneiss and a whole-rock sample of a conformable 

pegmatite. 

The scatter in apparent ages is very large (table 

1 ) . Five of the seven paragneiss samples do fit a 

single line on the isochron diagram (fig. 3), however, and this line corresponds to an age of 735

TABLE 1. Rb-Sr analytical data

RU o v Apparent 

Sample No. (p*^ } (j£m) Rbw/Sr" SrW/Sr" ^

Whole-rock paragneiss (Kigluaik Group) samples

70AcH-15 _ _ 87.2 130 1.949 0.7247 750

70AcH-16 101 199 1,467 .7193 732

70AcH-17 214 51.3 12.20 .8292 733

70AcH-21 _ 193 85.5 6.579 .7744 763

70AcH-26 _ _ 75.3 121 1.806 .7296 985

70AcH-27 ___ 150 283 1.536 .7180 639

68ASn-282 __ 137 79.2 5.024 .7293 357

Biotite from paragneiss (Kigluaik Group)

68ASn-282 __ 340 15.9 62,04 0.7920 102

Whole-rock segregation pegmatite

70AcH-18 209 307 1.975 0.7257 775

Whole-rock orthogneiss samples

70AcH-l _ 29.7 58.3 1.490 0.7316 1306

70AcH-2 _ 15.9 44.6 1.033 .7243 1380

70AcH-14 __ 228 25.8 26.07 .8821 489

70AcH-19 564 37.4 43.91 .7600 91

70AcH-20 359 40.9 25.74 .8393 376

70AcH-28 332 91.7 10.65 .7713 451

70AcH-30 _ _ 189 90.5 6.086 .7653 717

70AH-616 __ 55.8 115 1.406 .7157 581

70AH-617 __ 70.7 144 1.423 .7165 614 

68ASn-300 __ 109 116 2.736 .7136 714 

68ASn-282a _ 234 469 1.448 .7191 732 

68ASn-301B __ 516 77.9 19.34 .8051 374

K-feldspar from orthogneiss

68ASn-282a __ 321 219 4.251 0.7292 420

1 Assuming an initial SrSVSr88 of 0.7043.
C6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

0 84

082 -

080 -

078 -

0 76 -

0 74 -

0 72 -

0 70

FIGURE 3. Isochron diagram of Rb-Sr data for whole-rock 

paragneiss (Kigluaik Group) samples. Open circle is the 

segregation pegmatite sample 70AcH-18. Original SrsV 

Sr^O.7043; T=735 m.y.

m.y. (million years). Experience from other areas 

indicates that such whole-rock isochrons, for highrank metamorphic rocks, are commonly dating the 

time of metamorphism, and this is the interpretation that we make from these data. If this interpretation is correct, then the gneisses, which tend 

to occur as mantles around the Cretaceous intrusives, were metamorphosed much prior to the Cretaceous intrusion. The alternative explanation must 

be considered: The evidence for the original age of 

the slate of the York region and (or) other rocks 

that were metamorphosed to the dated gneisses was 

not seriously disturbed during the intrusion of the 

Cretaceous intrusives.

That the 735-m.y. age probably represents the 

time of metamorphism and not the age of the sedimentation or the age of the source terrane of the 

sediments is confirmed by sample 70AcH-18. This 

sample is from a conformable pegmatite. The pegmatite is entirely enclosed in paragneiss, and the 

field evidence indicates that it formed by segregation from the gneiss during metamorphism. Sample 

70AcH-17 is from the gneiss immediately adjacent 

to the pegmatite. A line connecting the two points 

places the time at which the samples were in equilibrium, in terms of strontium isotopic composition, 

at 725 m.y. ago, an age not significantly different

analytically from that obtained from the paragneiss 

samples. If our interpretation that the pegmatite 

is a segregation is incorrect and the pegmatite is 

actually of igneous origin, its age would still provide 

a minimum for the paragneiss unit.

Two of the Kigluaik Group paragneiss samples do 

not lie on the 735-m.y. isochron defined by the 

other samples. The sample that plots to the left of 

the line (70AcH-26) also has a peculiar Th/U. 

There is no obvious reason why 68ASn-282 plots to 

the right of the line and appears to give a young 

age. Biotite was separated from 68ASn-282 and 

analyzed for Rb, Sr, and Sr87 /Srso . The apparent age 

of the biotite is 103 m.y. if we assume the initial 

Sr87 /Sr80 of the paragneiss suite (0.7043 from fig. 3), 

or it is 80 m.y. if we assume that the biotite came 

into isotopic equilibrium with the whole-rock sample. In either assumption, the biotite age has been 

reset during Cretaceous time.

The Precambrian paragneisses of the Kigluaik 

Group are intruded by bodies of gneissic granite. 

The foliation of these orthogneisses tends to be 

parallel to that of the surrounding paragneisses. If 

this foliation was produced 735 m.y. ago, then the 

orthogneisses must also be of Precambrian age. Unfortunately, the Rb-Sr data for the orthogneiss samples do not define a single line (fig. 4; data given 

in table 1). The sample from near Nome (70AcH30), the two samples from Kawalik Mountain 

(70AH-616 and 70AH-617, fig. 1), and one sample 

from the Kigluaik Mountains (68ASn-282a) plot 

near the same isochron (solid line, fig. 4) as the 

paragneisses. The other samples from the Kigluaik 

Mountains give apparent ages both younger and 

older than 735 m.y. Five of these samples define a 

crude isochron of about 335 m.y. (dashed line, fig. 

4). One orthogneiss (70AcH-14) gives an apparent 

age of about 490 m.y., and another (70AcH-19), 

about 90 m.y. This scatter in the orthogneiss data 

can be interpreted in several ways, and no unique 

interpretation can be made at this time. Our preferred interpretation is that the orthogneisses are 

all of Precambrian age and that those in the 

Kigluaik Mountains have been more or less reset 

by the Cretaceous plutonism and tectonism. Thus, 

the crude alinement of the five samples along a 

335-m.y. isochron is fortuitous.

Sainsbury revisited the Kigluaik Mountains area 

in 1972 and 1973. He believes that these rocks 

(70AH-616 and 70AH-617) may be hybrid rocks 

formed by K-metasomatism of Precambrian rocks, 

the potash being derived from a granitic intrusive 

of Cretaceous age. If so, the anomalous ages de-
RADIOELEMENT CONCENTRATIONS, RADIOMETRIC AGES, KIGLUAIK MOUNTAINS, ALASKA C7

0.90

0.86 -

0.82 -

0.78 -

0.74 -

0.70

12 16 20 24 28 32 36 40 44

87 86 

Rb /Sr

FIGURE 4. Isochron diagram of Rb-Sr data for whole-rock orthogneiss samples. Solid line, T=735 m.y.; dashed line,

T=335 m.y.

rived for these rocks are explained on the basis of 

isotopic mixing.

To give credence to the 335-m.y. age would require that the orthogneisses of the Kigluaik Mountains formed by anatexis of a preexisting crustal 

rock 335 m.y. ago. This conclusion is based on the 

high initial Sr&7 /SrSG (0.720) of the 335-m.y. 

isochron. Such crustal anatexis would require an uncommon geothermal gradient, and presumably such 

an event would be manifest in other ways. No known 

evidence in the geologic record supports such an 

interpretation.

Inspection of figure 4 might also suggest that the 

335-m.y. isochron is a metamorphic isochron (that 

is, an older rock was metamorphosed at 335 m.y. 

causing the strontium isotopes to equilibrate between samples). The samples are too widely spaced, 

however, for such an interpretation to be plausible.

RADIOELEMENT DISTRIBUTION

The radioelement (RaeU, Th, and K) contents of 

all the major geologic units of the Kigluaik Mountains except an unnamed slate-phyllite-schist unit 

were determined. The purposes of this analysis were 

to confirm the presence of the regional high thorium 

contents found in a few early reconnaissance samples and to ascertain whether the various geologic 

units might have characteristic radioelement contents and ratios that could be used in reconnaissance mapping.

The radioelement contents of the samples collected near the Kigluaik Mountains are given in 

table 2 and are shown in relation to the geologic 

units in figure 5. Averages of radioelement contents 

and ratios in the rocks are given in table 3; values 

given in the literature for average radioelement contents in major categories of igneous rocks are included for comparison. The relation between Th and 

RaeU contents in the rocks of the Kigluaik Mountains is shown in figure 6A; similar data for RaeU 

and K contents are shown in figure 65.

The radioelement contents in the paragneiss samples of the Kigluaik Group are near the averages 

for intermediate igneous rocks (table 3). The RaeU 

content in the paragneiss is slightly lower than the 

average, and the high Th/RaeU and low RaeU/K 

indicate that the paragneiss may be depleted in 

RaeU. The depletion may be a near-surface effect of 

weathering and surface-water movement that has 

removed soluble Ra22G from the rock. The Th/K is 

close to the average for most igneous rocks, which 

indicates that the process causing the RaeU depletion had little effect on the other radioelements.

The orthogneiss samples appear to form two 

groups distinguished by the RaeU and K contents; 

the average Th content is nearly the same in both
C8 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 2. Concentrations and ratios of radioelements, Kigluaik Mountains, Alaska

Sample No. RaeU 

(ppm)

Th 

(ppm)

K

(percent)

Th

RaeU

RaeU

KX10-4'

Th

KXIO-*

Paragneisses of Kigluaik Group

70AcH-17 __. 

70AcH-21 __. 

70AcH-26 __. 

70AcH-15 __. 

67ATs-132 _. 

70AcH-16 __.

70AcH-27 __. 

70AcH-24 __. 

68ASn-282 _. 

68ATs-184-l 

68ATs-184-2

68ASn-282A 

68ASn-301B 

70AcH-28 __ 

70AcH-14 __ 

70AcH-20 __ 

70AcH-19 __

70AcH-30 __ 

70AcH-l _ 

70AcH-2 __ 

70AH-616 __ 

70AH-617 

67ATs-159 _ 

67ATs-80 __ 

67ATs-156 _ 

67ATs-163 _

67ATs-195 _ 

67ATs-223 _ 

67AKd-190 _

67ATs-156A 

67ATs-161 _ 

67ATs-197A 

67ATs-222 _ 

67AKd-212 _

70AcH-23 __ 

67ASn-3lA _ 

67ATs-184A 

68ASn-280 _ 

67ASn-124 _

0.37

1.07

.77

1.82

2.29

1.98

1.52

2.22

1.69

2.01

1.86

I.10

7.48

9.44

9.91

10.77

11.05

II.49 

15.21 

8.45 

19.31 

10.28

4.13

4.77

1.93

1.90

2.61

2.31

3.51

3.02

2.58

3.88

2.21

2.8 

7.0 

12.3 

5.4 

4.7 

5.6

7.6 

6.9 

5.0 

9.6 

5.5

0.09 

.22 

.40 

.96

.88 

.86

.43 

.74 

.66 

.52

.84

0.27

1.6

4.9

5.2

4.1

4.8

3.3 

5.0 

3.3 

5.0

4.6

Orthogneisses

9.76

12.66

6.30

7.60

15.21

11.93

3.28

3.60

1.82

3.17

3.69

39.48

41.46

42.25

33.79

39.87

51.91

25.95

45.99

52.35

28.34

27.81

4.79

4.67

4.20

4.56

4.04

4.20

2.38

.34

.26

1.20

1.46

4.0 

3.3

6.7 

4.4 

2.6 

4.4

7.9

12.8

28.8

8.9

7.5

2.0

2.7 

1.5 

1.7 

3.8 

2.8

1.4 

10.6 

7.0 

2.6 

2.5

8.2

8.9

10.1

7.4

9.9

12.4

10.9

135

202

23.6

19.0

Schists of the Nome Group

0.25

1.95

1.69

2.01

2.01

1.72

1.60

1.25

8.06

8.55

8.18

8.54

7.98

7.16

0.33

.98

1.61

.85

1.96

1.95

.39

5.0 

4.1 

5.1

4.1

4.2 

4.6 

4.5

Metagabbro

0.76

2.0

1.0

2.4

1.0

.88 

4.1

3.8 

8.2 

5.3 

9.6

4.4

4.1

18.4

0.39 

.41 

.35

,54 

.91

0.51

.40

1.21

1.63

1.94

0.01 

.08 

.25 

.62 

.12

1.3 

1.0 

3.5 

3.1 

2.1

39.0 

5.1

1.4

.87 

7.6

51.0

5.0

4.8

2.6

16.2

Cretaceous granitic rocks

3.44

3.97

4.52

6.17

8.25

26.99

41.39

27.85

48.48

57.39

4.15

5.15

4.60

4.49

4.52

7.9 

10.4 

6.2 

7.9 

7.0

0.83

.77 

.98

1.4

1.8

6.5

8.0

6.1

10.8

12.7

groups. The samples in one group contain more 

than 6 ppm RaeU and more than 4 percent K; samples in the other group contain less than 4 ppm 

RaeU and less than 3 percent K (table 3). The 

group with the higher RaeU and K contents has 

radioelement contents and ratios similar to those 

in typical alkali granites. The near-normal ratios in 

the samples indicate little disturbance or migration 

of the radioelements in the rock during metamorphism. The group containing lower amounts of 

RaeU and K appears to be either depleted in both 

of those radioelements or enriched in Th, and the

radioelement ratios are abnormal. The data indicate 

that the radioelement contents in the groups containing the lower RaeU and K have been altered 

greatly and that the two distinctively different types 

of rocks constituting the orthogneiss were either of 

different materials initially or were subjected to 

different conditions during metamorphism.

Most of the samples of schists of the Nome Group 

have radioelement contents similar to the averages 

for intermediate igneous rocks (table 3). The normal ratios of the radioelements (fig. 6) in most of 

the samples indicate that neither metamorphism nor
RADIOELEMENT CONCENTRATIONS, RADIOMETRIC AGES, KIGLUAIK MOUNTAINS, ALASKA C9

166°3CT 166°00' 165°30' 165°00'

65°15

65°00'

64°45'

;;;V •:'•'•:•. ;: ; V :y>-.p€g . --'- ;V-/-,

;:^;:^;:,,:;x r»N/.;V^-.V<;,,; v ; r : v ;/.;- '' '

EXPLANATION 

Raelf

ppm

RaeU 

< 1 

1-3

3-5 

>5

percent

K

« 1 

1-3 

3-5

>30

~ .; -- 

:&££V v i • v : v

EXPLANATION

Quaternary glacial deposits-Includes 

moraine and outwash material

Cretaceous igneous complex of Kigluaik 

Mountains-Includes rocks ranging 

from granite to diorite, and numerous 

roof pendants of Kigluaik Group

Precambrian 

Argillaceous limestone

Gabbro-lncludes gabbro and other 

highly altered mafic rocks

pGs--Slate, phyllite, and quartz siltite;

minor black limestone 

pGsb-Graphite-bearing biotite schist,

slate and calc-silicate rocks.

Believed to be metamorphosed

equivalent of pGs, but may be

an older unit

FIGURE 5.—Radioelement concentrations related to geology, Kigluaik Mountains area, Alaska.

'p€o' Orthogneiss-Derived from granites to quartz 

monzonites

Nome Group-Chloritic schists, metavolcanics, 

and thick marbles and micaceous marble 

schists; subordinate graphitic schists

Kigluaik Group-Includes an upper unit of calcsilicate rocks with numerous schistose 

marbles, a middle unit of marble gneiss, 

and a lower unit of paragneiss with 

calc-silicate rocks

recent weathering has preferentially mobilized the 

radioelements. The RaeU and Th contents of the 

schists of the Nome Group and the paragneiss of 

the Kigluaik Group are very similar, but the K contents are significantly different.

The lowest radioelement contents occur in gabbro 

and metagabbro, which intrude slate and chloritic 

schists. The gabbros occur as a series of small intrusives that trend northward in the western part 

of the Kigluaiks. The radioelement contents in the
CIO SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 3.—Averages of radioelement contents and ratios in rocks of the Kigluaik Mountains, Alaska, and summary of published averages for igneous rocks

Paragneiss of Kigluaik Group _ 

Orthogneiss : 

All samples

>6 ppm RaeU, >4 per-

<4 ppm RaeU, <3 percent K

Schists of Nome Group

Metagabbro _

Continental crust

Mafic

Silicic

RaeU

(ppm)

1.60 

7.18

10.6

3.11

1.61

.50

5.27

1.22 8

0.9

5 2.0 -2.6 5 4.7

5 4 

3 4.75

Th

(ppm)

10.4

39.0

41.5

36.1

7.10

1.13

40.4

Averages in igneous

"6 -10

10.0 

2.7

•"'8.5 -9.3

'20

'18

K

(percent)

2.98 

2.92

4.41

1.12

1.15

.21

4.58

rocks

4 1.6 -2.6

2 2.6 

'0.6 -0.75

4 2.7 -3.0 '3.6

2 3.79

Th

RaeU

6.6 

8.3

4.2

13

4.5

2.2

7.9

3 3.5-4

3.6 3 <3

2 4.8 6 4.1

"4.5

5 4.0

RaeU

K X 10-*

0.60 

3.5

2.4

4.8

1.7

10.8

1.2

i j

'2 0.6

7 0.7 -1

£ 1.29

2 1.3

Th

K X 10-4

3.8 

41

9.1

78

7.7

16

8.8

8 3.3

2 2.8

7 2.8-3.4

3 5.0 3 4.9

1 Rogers and Adams (1969b). 

2 Heier and Rogers (1963). 

3 Rogers and Adams (1969a). 

* Cocco and others (1970).

; Clark and others (1966). 

' Z. E. Peterman (written commun., 1963). 

Calculated from published values.

100

0.5

0.5 1.0 5 10 0.1 0.5 1.0 5 10

RaeU, IN PARTS PER MILLION K, IN PERCENT

EXPLANATION

• Precambrian Orthogneiss D Schist of the Nome Group 

o Paragneiss of the Kigluaik Group A Precambrian metagabbro

• Cretaceous granitic rock

FIGURE 6—Log-log plots of concentrations of radioelements in rocks of the Kigluaik Mountains, Alaska. A, Thorium 

(Th) versus uranium (RaeU). B, Uranium versus potassium (K).
RADIOELEMENT CONCENTRATIONS, RADIOMETRIC AGES, KIGLUAIK MOUNTAINS, ALASKA Cll

metagabbro are less than 0.9 ppm RaeU, less than 

2.0 ppm Th, and less than 0.7 percent K. Radioelement contents such as these are typical for basalts 

and gabbros.

The average Th and K contents of the Cretaceous 

granitic rocks and the Precambrian orthogneisses 

containing the greater abundances of RaeU and K 

are very similar (table 3). The characteristic that 

distinguishes the granitic rocks from the orthogneisses is the greater RaeU abundance in the orthogneiss. The Th content in both groups is about 

twice the average of that for silicic igneous rocks. 

The above-average thorium content in the Kigluaik 

Mountains samples is not unique. Similar Th contents have been reported (Rogers and Adams, 

1969a, p. 90-E-l) for Precambrian mica granites in 

the Ukranian shield (33 ppm average), second intrusive-phase alkalic granodiorites to alkalic granites in Tertiary Megrinsk intrusives of Armenia 

(32 ppm average), and the Mesozoic Con way Granite, an alkalic granite of New Hampshire (56 ppm 

average).

The radioelement analysis of the samples from 

the Kigluaik Mountains show that uncommonly high 

thorium contents measured in a few reconnaissance 

samples were representative and confirm the presence of regional high thorium contents. In this area, 

Th contents of about 25-55 ppm are common; a 

long-lived thorium-rich province is indicated by the 

similarity in the Th contents in the rocks of a wide 

range of geologic age. The data also show that most 

rocks in the major geologic units can be identified 

from the radioelement content and ratios.

Sainsbury reports that exploration for radioactive minerals during the years 1972-74 by AirSamplex Corp., under contract to Wyoming Minerals 

Corp., led to the discovery of highly radioactive deposits containing ore-grade concentrations of uranium and thorium along the eastward continuation 

of the Kigluaik and Bendeleben Mountains. Descriptions of these deposits have not yet been published.

We can conclude that the results of the work reported herein, which demonstrate the uncommonly 

high thorium content of many rocks in the Kigluaik 

Mountains, may be expected to delineate other belts 

of rocks favorable for the occurrence of primary 

deposits of uranium and thorium if applied elsewhere in Alaska. We hope that the data presented 

in this report will enable the researcher to recognize 

what must be considered abnormal variations and 

concentrations of uranium and thorium in rocks 

similar to those studied in the Kigluaik Mountains.

REFERENCES CITED

Brooks, A. H., Richardson, G. B., and Collier, A. J., 1901, 

Reconnaissance of the Cape Nome and adjacent gold 

fields of Seward Peninsula, Alaska, in 1900; A reconnaissance in the Norton Bay region, Alaska, in 1900, by 

W. C. Mendelhall: U.S. Geological Survey Special Publication, 222 p.

Bunker, C. M., and Bush, C. A., 1966, Uranium, thorium, 

and radium analyses by gamma-ray spectrometry (0.184- 

0.352 million electron volts), in Geological Survey Research 1966: U.S. Geological Survey Professional Paper 

550-B, p. B176-B181.

———— 1967, A comparison of potassium analyses by gammaray spectrometry and other techniques, in Geological 

Survey Research 1967: U.S. Geological Survey Professional Paper 575-B, p. B164-B169.

Clark, A. L., Berg, H. C., Cobb, E. H., Eberlein, G. D., MacKevett, E. M., Jr., and Miller, T. P., 1972, Metal provinces of Alaska: U.S. Geological Survey open-file report, 3 p.

Clark, S. P., Jr., Peterman, Z. E., and Heier, K. S., 1966, 

Abundances of uranium, thorium, and potassium, in 

Clark, S. P., Jr., ed., Handbook of physical constants: 

Geological Society of America Memoir 97, sec. 24, p. 

521-541.

Cocco, G., Fanfani, L., Zanazzi, P. F., Heier, K. S., and Billings, G. K., 1970, Potassium, chap. 19 of Wedepohl, 

K. H., ed., Handbook of geochemistry, v. 2, no. 2: New 

York, Springer-Verlag, p. A1-N1.

Heier, K. S., and Rogers, J. J. W., 1963, Radiometric determination of thorium, uranium, and potassium in basalts 

and in two magmatic differentiation series: Geochimica 

et Cosmochimica Acta, v. 27, no. 2, p. 137-154.

Hummel, C. H., 1962, Preliminary geologic map of the Nome 

C-l quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF247, scale 1:63,360.

Moffit, F. H., 1913, Geology of the Nome and Grand Central 

quadrangles, Alaska: U.S. Geological Survey Bulletin 

533, 140 p.

Patton, W. W., Jr., 1967, Regional geologic map of the 

Candle quadrangle, Alaska: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map 1-492, scale, 

1:250,000.

Rogers, J. J. W., and Adams, J. A. S., 1969a, Thorium, 

chap. 90 of Wedepohl, K. H., ed., Handbook of geochemistry, v. 2, no. 4: New York, Springer-Verlag, p. 

Bl-01.

———— 1969b, Uranium, chap. 92 of Wedepohl, K. H., ed., 

Handbook of geochemistry, v. 2, no. 4: New York, 

Springer-Verlag, p. Bl-01.

Sainsbury, C. L., 1969a, Geology and ore deposits of the 

Central York Mountains, western Seward Peninsula, 

Alaska: U.S. Geological Survey Bulletin 1287, 101 p.

———— 1969b, The A. J. Collier thrust belt of the Seward 

Peninsula, Alaska: Geological Society of America Bulletin, v. 80, no. 12, p. 2595-2596.

——— 1972, Geologic map of the Teller quadrangle, western 

Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-685; scale, 

1:250,000.
C12 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

———— 1974, Geologic map of the Bendeleben quadrangle, 

Seward Peninsula, Alaska: The Mapmakers, Anchorage, 

Alaska, 31 p.

———— 1975, Geology, ore deposits and mineral potential of 

the Seward Peninsula, Alaska: U.S. Bureau of Mines 

open-file report, 108 p.

Sainsbury, C. L., Coleman, R. G., and Kachadoorian, Reuben, 

1970, Blueschist and related greenschist facies rocks of 

the Seward Peninsula, Alaska, in Geological Survey Research 1970: U.S. Geological Survey Professional Paper 

700-B, p. B33-B42.

Sainsbury, C. L., Hedge, C. E., and Bunker, C. M., 1970, 

Structure stratigraphy, and isotopic composition of rocks 

of the Seward Peninsula, Alaska, in International Arctic 

Geology Symposium, 2d, San Francisco, 1971, Abstract 

Papers: American Association of Petroleum Geologists 

Bulletin, v. 54, no. 12, p. 2502-2503.

Sainsbury, C. L., Hummel, C. H., and Hudson, Travis, 1972, 

Reconnaissance geologic map of the Nome quadrangle,

Seward Peninsula, Alaska: U.S. Geological Survey openfile report, 28 p.

Sainsbury, C. L., Kachadoorian, Reuben, Hudson, Travis, 

Smith, T. E., Richards, T. R., and Todd, W. E., 1969, 

Reconnaissance geologic maps and sample data, Teller 

A-l, A-2, A-3, B-l, B-2, B-3, C-l, and Bendeleben A-6, 

B-6, C-6, D-5, D-6 quadrangles, Seward Peninsula, 

Alaska: U.S. Geological Survey open-file report, 60 p.

Sainsbury, C. L., Kachadoorian, Reuben, and Smith, T. E., 

1970, Fluorite prospects in the northwestern Kigluaik 

Mountains, Nome D-2 quadrangle, Alaska: U.S. Geological Survey open-file report, 8 p.

Sainsbury, C. L., Smith, T. E., and Kachadoorian, Reuben, 

1972, Reconnaissance geologic map of. the Nome D-3 

quadrangle, Seward Peninsula, Alaska: U.S. Geological 

Survey open-file report, 14 p.

Schonfeld, Ernest, 1966, Alpha M-An improved computer 

program for determining radioisotopes by least-squares 

resolution of the gamma-ray spectra: U.S. National 

Laboratories, Oak Ridge [Pub.] ORNL-3975, 43 p.
Chemical Variability of a Metavolcanic Rock Unit in the 

Tracy Arm-Fords Terror Wilderness Study Area, Alaska, and 

the Definition of Background Values for Geochemical Purposes

By J. D. HOFFMAN, D. A. BREW, C. L. FORN, and B. R. JOHNSON 

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-D

CONTENTS

Abstract ___._____________________

Introduction ________________

Acknowledgments ___ ________ _ 

Geologic setting ________________

Sample collection, processing, and analysis 

Statistical-analysis procedures _______.

Results and interpretations ________. 

References cited ________________

Page

Dl

1

1

1

2

3

4

ILLUSTRATIONS

Page

FIGURE 1. Map showing the Tracy Arm-Fords Terror Wilderness study area and vicinity and showing Coast 

Range batholithic complex, western metamorphic belt and intrusions within it, and locations of 

three quadrangles and eight traverses discussed in this report __ — __ — ___ — ______ — — ___ — __ D2

2. Graph showing the frequency distributions of the abnormally distributed elements before and after

log-transformation of raw data _________.________———_____—— ————— —— 5

3. Graph showing the variance components as percent total variance _______—____——__—_—_——__— 7

TABLES

Page

TABLE 1. Information on the eight traverses along which samples were collected for this experiment ___—__ D3

2. Means, standard deviations, and relative standard deviations for 18 elements in 156 rock samples from

the Tracy Arm-Fords Terror Wilderness study area, Alaska ________________——___—_——— 4

3. Computer-generated variance components for elements determined in samples from the Tracy ArmFords Terror Wilderness study area, Alaska __________________—___———_—___—_———__ 5

4. Variance components as percentages of total variance, and the significance of F-ratios derived from the

variance components ________________.______—_———__—_—__—_—————__ 6

5. Correlation coefficients of element concentrations in rock samples from the Tracy Arm-Fords Terror

Wilderness study area, Alaska _________.____________—_____—_—————_—____ 7

III

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

CHEMICAL VARIABILITY OF A METAVOLCANIC ROCK UNIT IN THE 

TRACY ARM-FORDS TERROR WILDERNESS STUDY AREA, ALASKA, 

AND THE DEFINITION OF BACKGROUND VALUES 

FOR GEOCHEMICAL PURPOSES

By J. D. HOFFMAN, D. A. BREW, C. L. FORM, and B. R. JOHNSON

ABSTRACT

Approximately 150 samples from a metavolcanic rock unit 

in the Tracy Arm-Fords Terror Wilderness study area, 

southeastern Alaska, were analyzed by routine U.S. Geological Survey semiquantitative spectrographic and analytical 

chemistry procedures. Of the 35 determinations performed on 

each sample, 18 were kept in the data set, and the resulting 

data were statistically analyzed to estimate (1) the distribution of each element about its mean concentration, (2) four 

components of chemical variability (using a hierarchical 

analysis of variance model), and (3) correlations between 

these elements. Over 75 percent of the total variance occurs 

at the lowest hierarchical level (between samples within 

sites) for Fe, Mn, Ba, Sc, V, and Y; thus, for these elements, 

so little geochemical variation is expected at map scales 

greater than a few meters that an enormous sampling effort 

would be required to define it. The sampled rock unit is geochemically homogeneous in these elements, at least in terms 

of mineral exploration surveys. Because of this, intense sampling is not necessary for further characterization of the 

distribution of these elements in the rock unit. On the other 

hand, Ca, Co, Cr, Cu, Ni. Ti, Mg, Sr, Zr, Pb, and Zn are 

not homogeneously distributed, and further sampling would 

be justified if map patterns for these elements are of interest.

INTRODUCTION

The wilderness study program of the U.S. Geological Survey and the U.S. Bureau of Mines consists of mineral-resource appraisal of generally 

large remote areas. The program relies heavily on 

geochemical studies to provide information on background abundance of certain elements in bedrock 

and stream sediments and on the abundance of 

metallic elements in mineralized rocks or areas. 

Most of the wilderness studies have used a tightly 

adjusted grid or other regular close-spacing procedure to select sample sites for background abundance information.

Recent (1973-1976) studies in the Tracy ArmFords Terror Wilderness study area, Alaska, provided the opportunity to test, by carefully designed 

sampling and analysis, the efficiency and the effectiveness of the close- and regular-spacing approach 

within an areally extensive metavolcanic rock unit. 

The ultimate purposes of the experiment were (1) 

to establish what kind of sampling and chemical 

analysis program is needed to adequately characterize the bedrock geochemistry for the determination of background abundance and for the recognition of any anomalously high values and (2) to provide this information for the guidance of others involved with wilderness-type studies.

ACKNOWLEDGMENTS

The authors are indebted to J. J. Connor and T. G. 

Lovering of the U.S. Geological Survey for technical 

review of the manuscript and to G. H. Allcott, also 

of the U.S. Geological Survey, for his helpful 

suggestions.

GEOLOGIC SETTING

The metavolcanic rock unit sampled is the most 

widespread in the western metamorphic belt adjacent to the Coast Range batholith complex in this 

part of southeastern Alaska (Brew and others, 

1977). The whole Tracy Arm-Fords Terror study 

area cuts across most of the batholithic complex and 

the rocks of the western metamorphic belt adjacent 

to it on the southwest (fig. 1). The batholithic complex consists of a remarkably long, foliated tonalite 

sill adjacent to a broad terrane of complexly deformed amphibolite-facies gneiss, marble, and some

Dl
D2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

BOUNDARY OF TRACY 

ARM-FORDS TERROR 

WILDERNESS AREA

COAST

METAMORPHIC

WmHolkha

COAST RANGE

MEGALINEAMENT

ZONE

BOUNDARY OF TRACY 

ARM-FORDS TERROR 

WILDERNESS AREA

FIGURE 1.—Tracy Arm-Fords Terror Wilderness study area 

and vicinity. Coast Range batholithic complex, western 

metamorphic belt and intrusions (patterned) within it, 

and locations of three quadrangles and eight traverses (including subtraverses 2-5) discussed in this report are 

shown.

schist in the northeast. Near the Canadian border, 

this terrane is intruded by a series of generally unfoliated granodiorite bodies of mid-Tertiary age, 

which are locally associated with migmatite zones.

The western metamorphic-belt rocks immediately 

adjacent to the complex are high-grade, highly deformed gneiss, schist, quartzite, and calc-silicate 

rock. To the southwest, the metamorphic grade diminishes abruptly, and complexly deformed greenschist-facies phyllite, slate, greenschist, and some 

limestone and quartzite are exposed over most of 

the area. The granitic rocks that locally intrude 

these low-grade metamorphic rocks with local contact-metamorphic effects are diorite, diorite porphyry, granodiorite, and hornblendite of inferred 

Cretaceous age.

The specific metavolcanic unit described crops out 

as a 61-km-long, 8-km-wide, irregularly shaped, 

northwest-trending belt. Although much of the unit 

contains appreciable quartzite, phyllite, semischist, 

and marble, the present study included only the 

dominant greenstone, greenschist, hornblende schist, 

and amphibolite. The unit is dominantly a greenschist metamorphic facies, but the metamorphic 

grade increases to the east-southeast; the unit there 

consists of hornblende schist, hornblende gneiss, and 

amphibolite. This increase in metamorphic grade is 

apparently regional and does not reflect any local 

intrusions.

The unit is probably metamorphosed volcanic 

rocks, carbonaceous shale, limestone, and chert. The 

nature and composition of the metavolcanics are 

uncertain: some of the greenstones and semischists 

probably were diabase intrusions; some may have 

been massive flows. At a few localities, the massive 

greenstones and greenschists contain relict pyroxene 

phenocrysts. The original age of the unit is unknown 

but is inferred to be Triassic or Permian on the basis 

of regional evidence. The age of metamorphism is 

inferred to be late Cretaceous.

The western metamorphic belt has long been 

recognized as having significant mineral-resource 

potential, and the unit studied here is the host rock 

for several known deposits, the most important of 

which are the Point Astley zinc-silver deposit and 

the Windham Bay lode gold deposit (both shown on 

fig. 1). These deposits consist of sulfide minerals, 

either disseminated through the unit or concentrated 

in lenses and stringers along the foliation within 

bleached or altered zones in phyllite. Although these 

deposits are within the greenschist and greenstone 

unit, these specific rock types are not common hosts.

SAMPLE COLLECTION, PROCESSING, AND 

ANALYSIS

The sample collection, processing, and analysis 

consisted of five successive stages: (1) selection of 

traverses for sampling within the bedrock unit (the
CHEMICAL VARIABILITY, METAVOLCANIC UNIT, TRACT ARM-FORDS TERROR AREA, ALASKA D3

highest geologically significant level in the hierarchical analysis), (2) the selection of sampling sites 

along these traverses, (3) collection of several 

samples at each of those sites, (4) processing of the 

samples for analysis, and (5) analysis by emission 

spectrography and by chemistry.

In selecting traverses (or in places portions of 

traverses), the distribution of the bedrock unit was 

considered first; all areas known or inferred to be 

influenced by local intrusions were eliminated from 

consideration, as were areas with heavy brush and 

timber. Then, all possible continuous traverses of 

about 1.5 km length were evaluated in the field, and 

the five crossing the greatest breadth of the metavolcanic rock unit were selected for study. The longest traverse was subdivided into four subtraverses 

(subtraverses 2-5). Data on the eight traverses and 

subtraverses selected are given in table 1.

Geologic features that might differentially affect 

samples on the five traverses are (1) the increase 

in metamorphic grade to the east-southeast; (2) 

the Coast Range megalineament (zone of prominent, 

parallel, closely spaced joints, foliation surfaces, and 

compositional layering several kilometers wide), 

which passes through part of the sampled area; and 

(3) an unexplained aeromagnetic anomaly (Brew 

and others, 1977, p. 79), near subtraverses 2-5, 

which could be generated by a narrow, shallow,

TABLE 1.—Information on the eight traverses along which 

samples were collected for this experiment

[Soacing between sites is 0.4 to 0.8 km. Spacing 

between samples is 1 to 10 m ]

Traverse 

number

1

2

3

4

5

6

7

8

Number of

Sites

6

3

3

3

3

4

6

5

Samples

29

13

14

14

16

17

29

24

Total 

traverse 

length (km)

1

1

1

1

1

.1

9

.3

.8

.5

Distance 

to next 

traverse (km]

4.4

3.0

2.9

6.6

1.5

Total 33 156 7.6

steeply dipping granitic dike. However, the influence 

of the metamorphism can be discounted because field 

evidence shows the unit is continuous throughout, 

and in the absence of evidence to the contrary, the 

metamorphism is assumed to have been isochemical. 

The megalineament probably had little influence 

because the bleaching and alteration of rocks parallel to it are consistently local, and such areas were 

avoided in the selection of sample sites. Calculations 

show that an aeromagnetic anomaly like the one 

described could be caused by a 600-m-wide body 

reaching to within about 700 m of the surface 

(Brew and others, 1977).

Sample sites along each traverse were selected 

according to the following criteria: (1) Each site 

had to be within a relatively large outcrop of greenstone and greenschist; (2) between-site spacing was 

about that commonly used (0.4-0.8 km) in reconnaissance geologic mapping and geochemical sampling in wilderness-type studies; and (3) several 

square meters of almost continuously exposed bedrock had to be present at each site. Four to seven 

samples were collected at each site; each sample was 

at least 1 meter and generally a few meters apart 

from another. This spacing was the only criterion 

used in selecting the exact sample positions. Each 

sample weighed about 50-100 g and consisted of 

chips taken from parts of about a square meter of 

rock.

The samples were bagged on the outcrop. They 

were submitted for preparation and analysis to U.S. 

Geological Survey laboratories in Denver, Colo. They 

were crushed and split. Each split was ground to 

about 75 fj.m (200 mesh) and analyzed for 30 elements by emission spectrography and for 5 elements 

by chemistry using routine procedures (Grimes and 

Marranzino, 1968; Ward and others, 1969). Altogether, 156 samples were collected, processed, and 

analyzed for the experiment. All analyses were performed in random order, and no replicate analyses 

were performed.

STATISTICAL ANALYSIS PROCEDURES

The results of the spectrographic and chemical 

analyses were statistically analyzed on the U.S. Geological Survey's DEC-10 computer in Denver, Colo., 

using STATPAC programs for Fisher-l? statistics, 

graphic analysis, correlation, and analysis of variance (VanTrump and Miesch, 1977). The analysis 

of variance program permits estimation of sample 

variances at each level of the sampling hierarchy. 

The statistical procedures used calculate (1) the
D4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

properties of the frequency distribution of each 

element, (2) the correlation between each pair of 

elements, (3) the geochemical variability within 

each level of the sampling hierarchy, (4) the statistical significance of this geochemical variability, by 

calculation of F-ratios, at each level of the hierarchy, 

and (5) the percentages of the total variance for 

each element at each level of the hierarchy.

Of the 35 separate elemental determinations on 

each sample, only 18 were used for statistical 

analysis. Because determinations of the other 17 

elements included a large number of values (more 

than 20 percent) below the detection limit for the 

element, the conventional statistical analysis of 

these elements could yield biased results. Even after 

exclusion of these 17 elements from the data set, 

determinations for a few samples were below the 

detection limits for some elements (Co, Cr, Cu, 

Ni); in these cases, such determinations were replaced by a value equal to half the detection limit. 

This widely used procedure is arbitrary, and its sole 

justification is the belief that substitution of any 

value at or below the detection limit would not 

materially change any geochemical conclusions 

drawn from the statistical analysis.

Determinations in the data set used in this study 

are for Fe, Mg, Ca, Ti, Mn, Ba, Co, Cr, Cu, Ni, Sc, 

Sr, V, Y, and Zr (determined by emission spectrography) and for Cu, Pb, and Zn (determined by 

atomic absorption spectrophotometry). In text and 

tables, elements with the prefix "AA" have been 

determined by atomic absorption; those without, by 

emission spectrography.

The hierarchical sampling procedure used is as 

follows: The study area is divided into three 20- 

minute quadrangles, which constitute the first, or 

highest, hierarchical level. The eight traverses (and 

subtraverses) are contained within these three 

quadrangles and compose the second hierarchical 

level. Along these eight traverses are 33 sites, which 

are the third hierarchical level. The 156 individual 

samples within the 33 sites constitute the fourth, or 

lowest, hierarchical level.

RESULTS AND INTERPRETATIONS

The means, standard deviations, and relative 

standard deviations of each element are shown in 

table 2. Graphic analysis and moments about the 

mean (Fisher-^ statistics) indicate that Fe, Mg, 

Ca, Ti, Co, Sc, Sr, Zr, AA-Pb, and AA-Zn are essentially normally distributed. Significant positive, or 

right, skewness exists for Ba, Cr, Cu, Ni, and V

TABLE 2.—Means, standard deviations, and relative 

standard deviations for 18 elements in 156 rock samples from the Tracy Arm-Fords Terror Wilderness 

study area, Alaska

Element Mean

Standard Relative standard 

deviation deviation (percent)

Fe (percent)---

Mg (percent)- —

Ca (percent) —

Ti (percent)—-

Mn (ppm)- — — --

Ba (ppm)--- — -

Co (ppm) — ---—

Cr (ppm) — -----

Cu (ppm) — ——-

Ni (ppm) — — —

Sc (ppm) -------

Sr (pom)--- — -

V (ppm) ----- -

Y ( ppm )- ———

Zr (ppm) ----- —

AA-Cu (ppm) - — -

AA-Pb (ppm) — -

AA-Zn (ppm) — —

7.0

2.8

3.9

0.6

1075

248

25

203

58

58

32

288

217

20

54

58

7

36

2.6

1.1

2.1

0.3

497.6

513.4

12.9

223.9

54.3

60.8

12.3

191.1

176.1

8.9

29.7

15.1

4.5

20.0

37

39

54

50

46

207

52

110

94

105

38

66

81

46

56

26

64

56

(fig. 2). Log-transformations were performed on 

the determinations of these five elements to determine if this approach would normalize the data 

(Davis, 1973). Graphic analysis of the transformed 

data yielded vastly improved distributions for V, 

suggesting that this element is lognormally distributed. Graphic analysis of the log-transformed data 

for Ba, Cr, and Ni showed significant improvement 

of the distributions of these elements, but logtransformation of Cu data yielded no useful improvement (fig. 2).

However, only nontransformed data are used in 

the statistical interpretation; differences in interpretation due to use of the lognormal data for some elements (Ba, Cr, Cu, Ni, and V) and the normal data 

for others are considered to be insignificant in the 

context of geochemical exploration. (An example of 

the statistical treatment of the log-transformed data 

is given in table 4). Moreover, statistical evidence 

indicates that if the relative standard deviation of a 

sample population is less than .120 percent, the 

greater efficiency of using log-normal data to estimate the mean of that population is outweighed by 

the possibility of introducing bias if the lognormal 

distribution is inappropriate. Further Finney's efficiency curve (Koch and Link, 1971) would not suggest the use of log-transformations, as the use of the 

raw data yields a statistical efficiency greater than 

90 percent for all elements in the data set except Ba. 

(That is, the sample mean of the nontransformed 

data is an estimator of the population mean more
CHEMICAL VARIABILITY, METAVOLCANIC UNIT, TRACT ARM-FORDS TERROR AREA, ALASKA D5

Ba Cr Cu

PARTS PER MILLION

Ni

FIGURE 2.—Frequency distributions of the abnormally distributed elements, before (dashed line) and after (solid

line) log-transformation of raw data.

than 90 percent of the time, even if the population 

is lognormally distributed.) Only Ba has a relative 

standard deviation higher than 120 percent.

Table 3 shows the variance components for each 

element at each level of the hierarchy. The computer 

program used to estimate these statistics is unable 

to distinguish very small variance components and 

may express this inability by the generation of

TABLE 3.—Computer generated variance components for elements determined in samples from the Tracy Arm-Fords 

Terror Wilderness study area, Alaska

[Inc., Inconsequential; component is so small that 

the computer generated a negative number for it, 

a statistical impossibility ]

Element

Fe— --

Mg - — — 

Ca———

Ti — — -

Mn ———

n _,

Co— —

Cr — — 

Cu — — 

Ni — —

Sr — —

V ————

Y ————

Zr———

AA-Cu— 

AA-Pb-- 

AA-Zn--

Between 

quadrangles

Inc.

Inc.

0.583^10°

Inc.

Inc.

5

Inc. 

Inc. 

Inc.

Inc.

.155x10""

.257x10""

_ i

Inc.

Inc. 

.156x10" 

.144xlO" 3

Between 

traverses

0. 274*10°

.576x10°

.651xlO~ 2

5

9] ? x i n~

.676x10"'

. 264x1 O" 5 

.126x10"" 

.270x10""

_ i

Inc.

Inc.

. 603x1 O" 1

3 

QD9 vl fl~

.902xlO" 3

.isoxio" 1

.609xlO" 2

Between 

sites

0.431x10°

.ssixio" 1

.243X10" 1

.321X1Q" 1

Inc.

.510x10"'

i

.720x10"" 

Inc. 

.696xlO~ 3

.510x10"

5

i 07 vi n~

.216x10""

.425x10"

.166xlO" 3

.166xlO" 3 

.436x10" 

.543xlO" 2

Between 

samples

0. 644x10"'

.819x10

.isixio" 1

.550X10" 1

6

245x10"

6

3

.320xlO" 5 

.295x10"" 

.182x10""

.146xlO" 3

5

9^Rxin~

_ 5 

*5r\n n r\~

.631x10"'

_"t

.203x10"" 

.134xlO" 2 

.177xlO" 3

negative variance components. These negative components suggest that an unusual sampling event occurred or, more likely, that the hierarchical analysis 

of variance program employed is unable to distinguish extremely small components of variance at 

hierarchical levels above the lowest level. If these 

components are small enough, they will contribute 

no significant variance and may be set to zero.

Table 4 and figure 3 display the variance components as percentages of the total variance at each 

hierarchical level. The data in this table indicate 

that for Fe, Mg, Ti, Mn, Co, Cr, Cu, Ni, Sc, Zr, and 

AA-Cu, the unit studied is essentially homogenous 

at the quadrangle hierarchical level, Ca, Ba, Sr, and 

V are homogenously distributed at the traverse 

level, and Mn and Cu are homogenously distributed 

at the site level. More than 50 percent of the total 

variance is explained at the sample level for Fe, Mg, 

Ti, Mn, Ba, Co, Cu, Sc, Sr, V, Y, AA-Cu, and AAPb. Mg, Co, Cu, Cr, Ni, and AA-Cu exhibit an interesting trend: low percentages of the total variance 

are contained in the quadrangle and site levels; 

much higher percentages of the total variance are 

explained at the traverse and sample levels. At the 

site level, this trend may be due to variation in the 

original composition of the metavolcanic rock unit 

sampled for the experiment.

Table 4 shows that for all but one of the elements, 

the percentage of the total variance explained by 

the variance between quadrangles is small. AA-Zn 

is the exception; the high variance at this level indicates that the distribution of Zn in the study area 

is unlike that of any other element. The distribution 

of Zn, in general, has not been fully explained (Park 

and MacDiarmid, 1975), and in these rocks it may 

represent either an original distribution, a secondary Zn (and Pb?) mineralization event, or even a 

later redistribution of this mobile element from
D6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 4.—Variance components as percentages of total 

variance and the significance of ~F-ratios derived from 

the variance components

[Differences between hierarchical levels are 

nonsignificant if no asterisk appears between 

columns ]

Hierarchical Level

Element

Quadrangle Traverse Site Sample

Variance components of normal data

Fe— —

Mg — —

Ca-----

Ti — —

Mn__

0 

0

12.1

0

n

3.8

0

6.9

« n

6.8

50.3

n

90.1

Q? n

BaCoCrCuNiSc- — - 

Sr- — — 

V—- — 

Y———— 

Zr— —

7.0

0

0

0

0

0

3.5

7.2

9.4

0

0

33.3

40.2

29.9

51.7

2.2

0

0

7.4

13.0

**

**

**

16.2

1.1

11.0

0

13.3

3.3

49.2

6.1

5.3

39.9

** 76.9 

65.6

** 48.8 

70.1

** 35.0

94.5

** 53.6 

86.7 

77.9

** 47.1

AA-Cu— 0 

AA-Pb— 7.4 

AA-Zn— 13.1

29.1 

8.5 

** 14.0

Variance components of

Cu- —— 5.7 

V ———— 7.7

2.5 

0

** 5.4 65.5 

20.6 ** 63.4 

12.4 ** 40.5

log-transformed data

6.3 * 85.4 

14.9 ** 77.4

* The difference between hierarchical levels is 

significant at the 0.10 alpha level.

**The difference between hierarchical levels is 

significant at both the 0.10 and 0.05 alpha levels.

either of these sources. The primary feature of this 

distribution is that it is regional in extent, and any 

explanation of Zn origin must take this into account. 

Fe is evenly distributed throughout the study 

unit, as is demonstrated by the lack of significant 

differences at all levels (table 4). More than 75 percent of the total variation in Fe, Mn, Ba, Sc, V, and 

Y lies at the sample hierarchical level, indicating essentially homogeneous distribution for these elements ; therefore, intense sampling over a large 

number of sites and traverses is not statistically

necessary to characterize the distribution of these 

elements (in the rock unit analyzed in this study). 

More intense site sampling will be required to establish the distribution of Co, Ti, Ni, Sr, Zr, AA-Pb, 

and AA-Zn, as a significant percentage of the total 

variance of these elements is at the traverse hierarchical level.

The significance of F-ratios derived from the variances within each level of the hierarchy is also 

shown in table 4. These ratios are tabulated for (1) 

traverses within quadrangles, (2) sites within 

traverses, and (3) samples within sites. There is no 

significant difference in variance between hierarchical levels in the distributions of Fe, Mn, Sc, and Y 

(see table 4) ; the distribution of the variances of 

these elements is even at all hierarchial levels. For 

16 elements, there is no significant difference between the quadrangle and traverse levels at either 

of the two alpha levels tested (0.05 and 0.10). The 

two exceptions are V at the 0.10 level and Zn at 

both alpha levels.

The statistical significance of the correlation coefficients (table 5) can be obtained using the standard normal (z) statistic:

where n is the number of samples, and r is the correlation coefficient. For this experiment, in which n 

equals 156, it can be shown that r values (alpha 

^0.05) beyond about ±0.16 are statistically 

significant.

From these findings (lacking replicate analyses 

to evaluate analytical variation) the writers conclude that the distribution of almost all the elements 

in the data set for this study unit could be adequately evaluated by (1) collecting more than one 

sample at any given site, in order to better characterize the distribution of the variances at the 

sample level because the largest variance component 

for all the 18 elements except Ca and Ni occurs at 

this level, (2) using significantly fewer sites along 

each traverse, as the site hierarchical level contains 

a relatively small variance component (less than 15 

percent of the total variance) for 12 of the elements 

in the data set, and (3) using a traverse spacing of 

3-7 km, the spacing used in this study. For example, 

statistically valid information on the bedrock background values for most of the 18 determinations in 

the data set could probably be obtained with just 

two sites along each of the eight traverses and subtraverses used and two samples at each site or with 

just one site on each traverse and four samples at 

each site. Either of these methods would yield a
CHEMICAL VARIABILITY, METAVOLCANIC UNIT, TRACY ARM-FORDS TERROR AREA, ALASKA D7

100

Variance between 

20-minute quadrangles

Eight traverses and

subtraverses 

Sampling sites within

traverses

Samples within sampling 

sites

Fe Mg Ca Ti Mn Ba Co Cr Cu Ni Sc Sr V Y Zr Cu Pb Zn

SPECTROGRAPHIC ANALYSIS

FIGURE 3.—Variance components, as percent total variance.

ATOMIC 

ABSORBTION

TABLE 5.—Correlation coefficients of element concentrations in rock samples from the Tracy Arm-Fords Terror Wilderness

study area, Alaska

[Significant correlations (i.e. 21 ±0.16) are underscored ]

Fe Mg Ca Ti Mn Ba Co Cr

1.00 0.40 0.08 0.41 0.62 -0.02 0.28 0.07

1.00 0.14 0.31 0.38 -0.04 0.47 0.57

1.00 0.11 0.39 -0.14 0.06 0.16

1.00 0.30 0.01 0.37 0.28

1.00 -0.10 0.20 0.12

1.00 0.10 0.09 

1.00 0.57

1.00

Cu

0.23 0

0.09 0 

-0.15 0 

0.14 0

0.14 0 

-0.08 0 

0.09 0 

-0.14 0

1.00 -0

1

Ni

.23

.60

.16

.42

.25

.09 

.62

.85

.06 

.00

Sc

0.09

0.10 

0.18

0.09

-0.02 

-0.07 

0.18

0.13

-0.11 

-0.02 

1.00

Sr

-0.10

-0.06 

0.50 

0.20

0.01 

-0.10 

0.03 

0.01

-0.12 

0.08 

0.14

1.00

V

0.63

0.18

0.17

0.54

-0.04 

0.06 

-0.03

iUZ 

0.05 

0.01

-0.10

1.00

Y

-0.02

-0.04 

0.06 

0.36

-0.12 

0.08 

0.24

0.06

-0.15 

0.09 

0.27

0.28

-0.20

1.00

Zr

-0.11

-0.01 

-0.11 

0.42

-0.15 

0.33

0.27 

0.16

-0.15 

0.22

0.00

0.29

-0.34

0.60

1 .00

AA-Cu

0.07

0.02 

-0.10 

-0.01

0.01 

-0.08 

0.05 

-0.14

0.84

-0.10 

-0.10

-0.02

0.09

-0.16

-O.J8

1.00

AA-Pb

-0.03

0.13 

-0.19

0.06

-0.15 

OJ3. 

0.10 

£.2.3

-0.07 

0.23

0.00

-0.02

-0.07

0.09

0^23.

-0.11

1 .00

EleAA-Zn ment

0.

-0. 

-0.

0.

-0.

0.

-0. 

-0.

0. 

-0.

0.

-0,

-0.

0.

o.

0.

0,

1.

.08 Fe

03 Mg 

.48 Ca

.12 Ti

.16 Mn

.17 Ba

.01 Cc 

.14 Cr

.13 Cu 

.09 Ni 

.00 Sc

,16 Sr

.05 V

.15 Y

.18 Zr

.07 AA-Cu

J>£ AA-Pb

.00 AA-Zn

total of 32 samples, instead of the total of 156 samples used in this study. For background information 

on a rock unit such as that described herein, a typical U.S. Geological Survey wilderness-type bedrock 

sampling program would involve 50-60 samples.

The conclusions from this experiment may apply 

to other areas with similar lithologies and can 

probably be used for general guidance, but experiments of the same type, done early in the geochemical study of a given area, could help establish an
D8 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

effective system for determining background values 

and thus aid in the organization of an effective 

sampling program.

REFERENCES CITED

Brew, D. A., Grybeck, Donald, Johnson, B. R., Jachens, R. C., 

Nutt, C. J., Barnes, D. F., Kimball, A. L., Still, J. C., 

and Rataj, J. L., 1977, Mineral resources of the Tracy 

Arm-Fords Terror Wilderness study area and vicinity, 

Alaska: U.S. Geological Survey Open-File Report 77- 

649, 282 p.

Davis, J. C., 1973, Statistics and data analysis in geology: 

New York, John Wiley and Sons, v. 2, 813 p.

Grimes, D. J., and Marranzino, A. P., 1968, Direct-current 

arc and alternating spark emission spectrographic field

methods for semiquantitative analysis for geologic materials: U.S. Geological Survey Circular 541, 6 p.

Koch, G. S., Jr., and Link, R. F., 1971, Statistical analysis 

of geological data: New York, John Wiley and Sons, v. 

2, 417 p.

Park, C. F., Jr., and MacDairmid, R. A., 1975, Ore deposits 

(3d ed.) : San Francisco, W. H. Freeman and Co., 529 p.

VanTrump, George, Jr., and Miesch, A. T., 1977, The U.S. 

Geological Survey RASS-STATPAC system for management and statistical reduction of geochemical data: 

Computers & Geosciences, v. 3, no. 3, p. 475-488.

Ward, F. N., Nakagawa, H. M., Harms, T. F., and Van 

Sickle, G. H., 1969, Atomic absorption methods useful 

in geochemical exploration: U.S. Geological Survey Bulletin 1289, 45 p.
Efficient Stream-Sediment Sampling Design: 

An Experiment at Tracy Arm, Alaska

By BRUCE R. JOHNSON, CARL L. FORN, JAMES D. HOFFMAN, 

DAVID A. BREW, and CONSTANCE J. NUTT

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-E

An application of analysis-of-variance techniques 

to the problem of sampling design for 

regional stream- sediment geochemical surveys

CONTENTS

Page

Abstract _____________________________________ El

Introduction _____________________________________ 1

Sampling and chemical analysis ___________________________ 2

Statistical analysis _________________________________ 3

Sampling design _______________________________________ 7

Conclusions and recommendations __________________________- 8

References cited ____________________________________ 8

ILLUSTRATIONS

Pa#e

FIGURE 1. Geologic map of study area at Tracy Arm _______________________________________ E2

2. Sketch map showing design of sampling program at Tracy Arm __________ — ______ — — -___ — ___ 3

3. Diagram showing variance components, as percentage of total variance, by element _—________________ 6

TABLES

Page

TABLE 1. Sampling and separation procedures which yield the greatest mean concentration of selected elements.-- E3

2. Detection limits of analyses and number of coded values reported for each element ________________ 4

3. Variance components, means, and approximate confidence limits for selected elements ____________ 5

in

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

EFFICIENT STREAM-SEDIMENT SAMPLING DESIGN: 

AN EXPERIMENT AT TRACY ARM, ALASKA

By BRUCE R. JOHNSON, CARL L. FORN, JAMES D. HOFFMAN, 

DAVID A. BREW, and CONSTANCE J. NUTT

ABSTRACT

A total of 371 stream sediment samples were collected from 

a 150-km - drainage north of Tracy Arm, Alaska. The basin 

contains approximately 45 km of first- and second-order active stream channels. Nearly 1,700 splits of these samples 

were analyzed for 30 elements by speetrograph and for 4 

elements by atomic absorption using standard U.S. Geological Survey techniques. Variance components, derived from a 

four-level hierarchical-design analysis of variance, were 

found to vary widely among the elements. For most elements included in the study, variations among samples 

spaced less than 1.5 km along active stream channels are insignificant compared with variations at 1.5-km spacings (the 

largest spacings tested by the model). For many of the elements analyzed in this study, particularly those determined 

by spectrograph, approximately one-half of the total variation is a result of sample preparation and analysis in the 

laboratory. This is an indication that the study area did not 

contain large geochemical anomalies. To reduce the effects of 

this analytical noise, it is necessary to collect more than one 

sample at each sample location or to run replicate analyses 

of each sample.

INTRODUCTION

A stream-sediment sampling experiment was 

undertaken as part of the U.S. Geological Survey 

wilderness resource evaluation program in the 

Tracy Arm-Fords Terror Wilderness study area, 

southeastern Alaska (Brew and others, 1977). The 

primary objective was to develop sampling plans and 

data analysis techniques that make the most effective use of the time and resource,* available for 

sampling active stream sediments. These techniques 

may be useful in improving the quality of future 

resource evaluation programs in southeastern 

Alaska and other areas of similar terrain and bedrock geology.

Geochemical information is usually presented in 

the form of contour maps of the abundance of one

or more elements of interest. Such maps are intended to show background amounts of the element 

in question as well as areas of anomalously high 

amounts of that element. The size, intensity, and 

location of these anomalies form the basic information useful to a resource evaluation program. With 

the increased efficiency of computer-generated statistical analysis and automatic contour plotting, it is 

much easier to generate anomaly maps than it is to 

assess their quality. Therefore, a second objective of 

the sampling experiment was to assess the stability, 

or reproducibility, of maps generated by current procedures.

Previous studies of this problem have generally 

stressed the need for formal randomization procedures at all stages of the analysis to ensure the 

validity of subsequent statistical procedures (Eisenhart, 1947; Krumbein and Slack, 1956; Miesch, 

1976). Although such procedures are ideal in terms 

of statistical theory, they are often impractical for 

large resource-assessment programs. This study is 

designed to help bridge the gap between more 

formal statistical techniques and the real world of 

deadlines and budgets.

To generate a data set for testing current procedures, a drainage area north of Tracy Arm (fig. 1) 

was sampled intensively. A hierarchical- or nesteddesign analysis of variance was used to estimate the 

components of total sample variance that are related 

to different sample spacings as well as the analytical 

variance. For many elements analyzed by spectrographic techniques in this study, approximately onehalf of the total sample variance is the analytical 

component. To reduce this component so that small 

anomalies may be differentiated from the analytical 

noise, it is necessary to collect more than one sample

El
E2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

133°25'

58°00'

EXPLANATION

Glacial ice and 

permanent snowfields

Tertiary granodiorite and 

associated migmatite

Cretaceous(?) gneiss 

and schist

Cretaceous(?) marble 

and calc-silicate gneiss

Cretaceous(?) or older 

ultramafic rocks

Boundary of study area

Stream channel with 

sampling location

Contact-Dotted where 

inferred

FIGURE 1.—Geologic map of study area at Tracy Arm. Geology from Brew and others (1977).

from each sample location and (or) analyze each 

sample more than once.

SAMPLING AND CHEMICAL ANALYSIS

The drainage basin chosen for this study lies on 

the north side of Tracy Arm and covers an area of

approximately 150 km2 (fig. 1). The bedrock underlying the basin is composed primarily of hornblendebiotite granodiorite and associated migmatite and 

host rocks of amphibolite-grade gneiss and schist. 

Small areas of marble and calc-silicate gneiss are 

included in the host rocks as are several small ultramafic bodies (Brew and others, 1977). Elevations in
EFFICIENT STREAM-SEDIMENT SAMPLING: AN EXPERIMENT AT TRACY ARM, ALASKA E3

the drainage basin range from boundary peaks 

approximately 2000 m high to sea level at the mouth 

of the main stream. In addition to the main stream, 

eight first-order tributaries are contained within the 

basin.

To perform a hierarchical analysis of variance, the 

basin was first divided into 27 sampling locations 

(fig. 1). Each location was subdivided into sites, and 

sample points were randomly located within each 

site (fig. 2). A sampling location was defined as a 

few hundred square meters of active stream sediments that could be sampled by hand. The average 

distance between the centers of sampling locations, 

measured along the stream course, was about 1.5 

km.

Within each sampling location, one to five sites 

were selected at random. If the location included a 

stream junction, all tributaries were sampled. A site 

was defined as an area of several square meters 

from which active stream sediment could be collected. It should be emphasized that formal randomization procedures were not followed for site 

selection. The collecting geologist was instructed to 

select sites within a location at random and to include all tributaries. Because the possible number of 

sites that could be selected was virtually unlimited 

and the statistical techniques used are believed to 

be robust (Cochran, 1947), lack of formal randomization should not seriously affect the results. Originally three sampling sites were to be chosen within 

each location, but the realities of accessibility limited the number to one or two at some locations, 

whereas within others four or five sites could be 

selected. The average distance between the centers 

of sites within a location was about 100 m.

Within each site, samples were collected from one 

to four separate points. Again, random selection of 

sampling points within each site was left to the 

geologist. At each collection point, both a normal,

Active/'

stream

channel

Samples

Accessible

active 

sediments Sample points 

FIGURE 2.—Design of sampling program at Tracy Arm.

fine-grained sample and a visibly coarser grained 

sample were collected. The samples were dried in the 

field and shipped to the U.S. Geological Survey's 

Mobile Analytical Lab in Juneau, Alaska, for 

processing.

At the laboratory, the samples were each sieved 

at 80 mesh to separate coarse and fine fractions. At 

this stage, there were four sample fractions from 

each sampling point: a coarse ( + 80 mesh) and a 

fine ( — 80 mesh) fraction of both the normal and 

the coarser samples. Each fraction was then pulverized and split so that replicate chemical analyses 

could be performed. Three splits were obtained from 

the fine fraction of the normal samples, and two 

splits were obtained of all other fractions. In all, 

1,669 splits were analyzed by standard Geological 

Survey procedures for 30 elements by spectrographic 

techniques and for an additional 4 elements by 

atomic absorption techniques (Grimes and Marranzino, 1968; Ward and others, 1969).

STATISTICAL ANALYSIS

Frequency curves of the results reported by the 

analytical laboratory were plotted as an initial step 

in the data analysis. The curves were examined to 

determine which of the four combinations of sample 

collection and treatment produced the greatest mean 

concentration of each element. The common technique of collecting fine-grained samples and analyzing the fine fraction produced the greatest concentration of most, but not all, elements. If the intended 

survey were aimed specifically at magnesium and 

calcium, for example, a greater concentration would 

probably be found (in this study area) in a coarser 

original sample (table 1).

TABLE 1.—Sampling and separation procedures which 

yield the greatest mean concentration of selected elements

[Spec, analysis by emission spectrography. A. A., analysis by atomic 

absorption]

Sample

Fine

Coarse

Split 

(mesh)

+80

-80

+80

-80

Spec

A. A.

Spec

A. A.

Spec

Spec

Greatest mean 

concentration

Be

Pb

Ba, Co, Cr, Cu, Fe,

Ni, Sc, Sr, Ti, Zn

Cu, Zn

Pb

Ca, La, Mg, Mn, V, Y
E4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

However, for a multielement geochemical survey, 

the —80 mesh fraction of a fine-grained sample 

seems to be preferable.

Subsequent statistical analyses were carried out 

simultaneously and separately on data from each of 

the four sample fractions. Because the —80 mesh 

fraction of the fine samples appeared to produce the 

best data, the rest of this discussion will concentrate 

on the data obtained from these samples.

All spectrographic analytical data were reported 

either as a six-step logarithmic scale, with the following numbers representing the centers of the 

intervals,... 1,1.5, 2, 3, 5, 7 .. ., or by an alphabetic 

code (Ward and others, 1963; Grimes and Marranzino, 1968). The number of analyses falling into 

each of the coded classes as well as the detection 

limits in use are tabulated in table 2. Because distributions with a large number of values above or 

below detection limits are not compatible with 

analysis of variance techniques, all sample distributions with more than 25-percent coded values were 

eliminated from the remainder of the analysis. 

Thus, spectrographic analyses of 13 elements (table 

2) were eliminated, as was atomic absorption analysis of gold. However, there is no evidence that distributions of these elements differ substantially 

from those of the remaining elements. The other 20 

elements had less than 25-percent coded values and 

were used in the hierarchical analysis of variance.

Examination of the frequency curves showed the 

sample distributions to be positively skewed almost 

without exception. Because logarithmic transformation of the data removes much of the skewness, the 

original population distribution was assumed to be 

closer to lognormal than normal. Because analysisof-variance techniques assume a normal sample distribution, all sample data were converted to their 

logarithms before performing the analysis of 

variance.

All coded values must be replaced by numeric 

values for the analysis of variance. For this analysis 

all values coded N and L (table 2) were replaced 

with a numeric value one step below the detection 

limit for that element, and all values coded G were 

replaced with a numeric value one step above the 

maximum comparison limit (see Miesch, 1967, for 

more exact methods of treating censored data).

A four-level hierarchical-design analysis of variance was performed on the data for each element 

using the U.S. Geological Survey's STATPAC program D0038 (Sower and others, 1971; George Van 

Trump, unpub. data, 1972). This program generates 

variance components for each hierarchical level

TABLE 2.—Detection limits of analyses and number of coded 

values reported for each element

[Number of analyses, 555; except for Au by atomic absorption, 185 analyses. Analyses of fine fraction of fine samples. N, not detected; L, detected but below comparison limit; G, greater than maximum comparison 

limit]

Analytical limits Analytical values reported

Element

Fe—

MgCa—

Ti—

(Ag)-

(As)-

(Au)-

(B)-

Ba—

(Be)-

(Bi)-

(Cd)-

CoCr—

Cu--

La—

Mn—

(Mo)-

(Nb)-

Pb- 

(Sb)-

Sc— 

(Sn)-

Sr—

V — -

Y — - 

(Zn)- 

Zr-

(Au)- 

Cu— 

Pb— 

Zn—

Lower Upper

Within 

analytical 

limits N

SPECTROGRAPHIC ANALYSES

0.05% 

.02 

.02 

.002 

0.5 p pm 

200 

10 

10 

20 

1

10

20

5

10 

5

20

10

5

20 

5

10

100

5

10

100

10

50

10

200

10

1

554 

548 

555 

539 

7 

0 

0

84

5,000 ppm 549

211

0

0

555

555

555

452

555

4

4

555

428

0

555 

0

555

555

0

555 

2

0

0

0

0

537

555

555

257 214

0 0

40 304

555

555

0

0

0

76

0

550

375 176

0 0

13 114

555 0

0 0

555

0

0

555

0

552

0

0

0

0

0

27

0

1

1,000 554 0

ATOMIC ABSORPTION ANALYSES

0.05 ppm

5

5

5

1

555

524

555

184 0

0 0

0 31

0 0

1

7

0

16

0

0

0

0

6

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

Elements in parentheses were not used for analysis of variance. 

2 Upper comparison limit shown only where G codes were reported.

along with the total sample variance for each element. A variance component is that portion of the 

total sample variance that can be attributed to variations at a particular hierarchical level (Krumbein
EFFICIENT STREAM-SEDIMENT SAMPLING: AN EXPERIMENT AT TRACT ARM, ALASKA 

TABLE 3,—Variance components, means, and approximate confidence limits for selected elements

E5

Element

Total 

variance 

of log(X)

Variance components

Location Site Sample

Geometric

Analytical mean

Analytical 

standard 

deviation

Approximate

95% confidence 

3 limits (steps)

SPECTROGRAPHIC ANALYSES

Fe -——

Mg ———

Ca ———

Ti ———

Ba ———

Co ———

Cr ———

Cu ———

La ———

Mn ———

Ni ———

Pb ———

Sc ———

Sr ———

V ———

Y ———

Zr ———

Cu ———

Pb ———

Zn ———

0.028

.027

.031

.055

.047

.032

.090

.083

.096

.021

.083

.009

.022

.043

.016

.042

.069

0.031

.025

.034

16.

23.

19.

3.

36.

41.

49.

11.

12.

6.

54.

4.

16.

26.

2.

1.

7.

36.

31.

33.

8

6

8

9

3

6

8

2

3

8

7

6

0

3

5

1

4

4

6

1

17.2

9.7

11.2

8.2

10.9

8.1

14.1

7.5

10.4

4.5

12.8

13.3

17.7

24.9

9.3

4.9

7.3

8.5

2.9

32.8

4.8

0

0

0

5.1

9.2

2.1

15.9

21.9

0

10.5

0

9.5

0

0

24.6

28.3

ATOMIC

36.0

8.6

26.4

61

66

69

87

47

41

34

65

55

88

22

82

56

48

88

69

57

.1

.7

.0

.9

.8

.1

.0

.4

.4

.7

.0

.1

.9

.8

.2

.4

.1

ABSORPTION

19

57

7

.1

.0

.7

5.1%

2.8

5.7.

.47

1500 ppm

20

180

32

54

1100

62

12

24

360

IbO

29

150

ANALYSES

28 ppm

7

39

0.13

.15

.15

.24

.16

.11

.18

.23

.30

.14

.14

.17

.11

.14

.12

.17

.20

0.08

.13

.05

1

2

2

3

2

1

2

3

3

1

1

2

1

1

1

2

2

1

1

.5

.5

.5

.5

.5

.5

.5

.b

.5

.5

.5

Percent total variance of log(X).

-Geometric mean is the antilog of the mean of log(X).

Atomic absorption results were not reported on the six-step scale. For purposes of comparison, the 

confidence limits have been converted to equivalent scale steps.

and Graybill, 1965, p. 209). The four levels used in 

this study were (1) sampling locations, (2) sites, 

(3) sample points, and (4) repeat analyses. The 

results of the analysis are tabulated in table 3, and 

the variance components are displayed in figure 3.

The most striking aspect of the variance components is the lack of pattern or uniformity from element to element. There are large differences in the 

variance distribution among levels from one element

to another and also significant differences in total 

variation between elements. Some patterns do 

emerge, however. In general, about one-half of the 

total sample variation is generated during the sample 

preparation and analysis, about one-fourth of the 

variance is due to differences between sample locations, and the remaining one-fourth is due to differences between sites within sampling locations and 

between sample points within sites. The fact that
E6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

CO

CO

<

Z 

<

20 40 60 80 100 

VARIANCE COMPONENTS, IN PERCENT

EXPLANATION 

Location

Site

Sample

Analytic

FIGURE 3.—Variance components, as percentage of total variance, by element.

components of variance for site and sample point 

levels are generally significantly smaller than the 

components for locations is encouraging because the 

sampling locations are spaced typically for a regional 

analysis project. Thus, spacing sample locations any 

more closely is probably not necessary in this area 

for defining geochemical background levels and detecting significant anomalies.

The generally large analytical variance may cause 

a great deal of information to be lost if normal 1 X 1 

(one sample per location, one analysis per sample) 

sampling techniques are used. There are exceptions, 

however, so that each element and each analytical 

technique must be considered separately.

The fact that the analytical variance accounts for 

about one-half of the total variance in this data 

should not be considered a criticism of the analytical 

technique. It is an indication that the analytical variance and the remaining sample variance are approximately the same magnitude. If the sample population 

were totally homogeneous, foT example, the analytical variance would account for all the total variance. 

Because the study area did not contain any large 

anomalies, the sample variance was small. Large 

anomalies would have shown up despite the analytical noise in a 1 x 1 sample design. However, much 

of the background information would have been lost.

The precision of the analytical techniques can be 

estimated from the analytical variance components. 

Using standard statistical techniques, 95-percent 

confidence limits can be estimated for each element 

by doubling the analytical standard deviation and 

adding to and subtracting from the log of the value 

in question (Krumbein and Graybill, 1965). Antilogs 

of these values can be found to convert the confidence 

limits to parts per million or percentages. Conversion can also be made to the number of steps up or 

down the six-step spectrographic scale at which the 

approximate 95-percent confidence limits lie. These 

limits are given in table 3.

The interpretation of these limits is best explained 

by an example: From table 3, the 95-percent confidence limits for copper analyzed spectrographically 

are plus and minus 3 steps. If the laboratory reported a single analysis of a single sample as having 

100 ppm copper, we would expect the true amount of 

copper in the sample to lie between 30 and 300 ppm 

with probability 0.95. That is, we would expect the 

true value to be more than 3 steps away from the 

reported value 1 time in 20 for all such analyses of 

copper. The analytical precision values reported here 

appear consistent with a recent study by Motooka 

and Grimes (1976), in which they analyzed 22 dif-
EFFICIENT STREAM-SEDIMENT SAMPLING: AN EXPERIMENT AT TRACT ARM, ALASKA E7

ferent samples over 2,700 times using the same 

analytical techniques.

A comparison with the confidence limits for copper 

measured by atomic absorption points out the need 

to study the problem separately for each element and 

each technique. The 95-percent confidence limits in 

this instance are plus and minus 1 step. For a sample 

reported as having 100 ppm copper by this technique, 

we would expect the true amount of copper to be 

between 70 and 150 ppm with probability 0.95.

SAMPLING DESIGN

The approach used in this experiment is obviously 

not suited to routine large-scale geochemical sampling programs, but it does provide a test of such 

programs. Such a program uses only one suite of 

samples to detect anomalous occurrences of 20 or 

more elements. For each element of interest, a contour plot is normally generated that shows areas 

above some threshold value as being anomalous.

One measure of the quality of such a map is its 

stability. If repeating the entire experiment, including resampling and reanalyzing, would produce a 

map that was essentially the same as the original 

map, then the original would be considered quite 

stable. Fortunately, it is not necessary to actually 

repeat the experiment to measure the map stability. 

Miesch (1976) devised a statistical procedure for 

measuring map stability based on calculation of the 

variance mean ratio (vm ). He concluded that if vm 

is less than 1, the geologic pattern of the area will 

not be stable. If vm is greater than 1, the pattern is 

more stable, and, as v», approaches 3, the map b&- 

comes quite stable (Meisch, 1976, p. 102). An example of the calculation of vm is shown as follows:

According to Miesch (1976), 

vm = N0 /Dm , 

where

vm is the variance mean ratio,

Nv is the sampling location variance component,

and

Dm is the variance of sampling locality means. 

Dm is estimated by

Dm = (ss2 /ns) + (sA2 /(nsnA )), 

where

ss2 is the combined site and sample point variance components,

sA2 is the analytical variance component, 

ns is the number of samples per sampling location, and 

nA is the number of analyses per sample.

Assuming a hypothetical average element with Nv of 

0.012, site and sample-point variance components of 

0.006 each (s,s.2 = 0.012), and SA- of 0.028, vm may be 

calculated for any combination of nH and nA , as 

follows:

7U=1 n*=2 nA=B nA=4

1

2

3

4

0.3

.6

.9

1.2

0.5

.9

1.4

1.8

0.6

1.1

1.7

2.3

0.6

1.3

1.9

2.5

Because variations at the site and sample-point 

levels in this study were found to be relatively insignificant, all map stability calculations are based 

on a sample location separation of approximately 

1.5 km. Because one suite of samples must be collected for all elements, the calculations have been 

done using a hypothetical average element. The variance components for this average element were 

obtained by taking the mean components of all 

elements shown in table 3. Any single element or 

other combination of elements deemed to be more 

important could be used as well.

By using variance components of an average element and combining site and sample-point variances, 

the problem is resolved into a question of how many 

samples to collect at each sample location and how 

many replicate analyses to make of each sam'ple.

It is clear from the calculations shown that the 

standard 1x1 sample design has very poor map 

stability for the average element used. If a vm of 

approximately 1.0 is considered a minimal acceptable 

level of map stability for reconnaissance work, then 

the calculations show that either a 2 x 2 design or 

a 3 x 1 design might be sufficient. Even better would 

be a 4 x 1 design. These conclusions are valid for 

this particular study area, which has no large anomalies. An area with larger anomalies would have a 

larger sample variance and would allow a simpler 

sample design to maintain the same vm.

To select the most cost-efficient sample design, the 

costs of sample collection and analysis must be 

known. Analytical costs are usually known as a constant per analysis as long as the total number of 

analyses is large. The cost of collecting each sample 

generally decreases as the number of samples collected at each location increases. Estimates of field collection expenses should be based on collecting up to 

about four samples per sampling location. At that 

point, it shiould be possible to estimate costs per sampling location for the various sampling designs. In 

the example above, the 2x2 design is more eco-
E8 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

nomical if sample collection costs exceed analytical 

costs, whereas the 3x1 design is more economical 

if analytical costs are higher.

Finally, an estimate of total costs for sampling 

and analysis can be made from the sample design 

chosen and the projected number of sampling locations within the project area. If this total exceeds 

the resources available, a few options remain. The 

first is to increase the spacing between locations. 

The effect will be to increase the areal size of the 

smallest details visible in the final maps. Another 

option may be to cut the analytical costs by limiting 

the number of elements. Finally, it may be possible 

to enhance anomaly contrast by selective concentration of specific minerals. This procedure might make 

a simpler and cheaper sample design possible.

The specific goals of the survey must always be 

kept in mind. Generally, a geochemical survey is intended to (1) detect large anomalies, (2) estimate 

geochemical background levels, (3) detect subtle 

broad halos, or some combination of these. Spacing 

between locations and map stabilities that are adequate for one set of goals may not be for another. 

In any case, using a sample design that produces a 

map stability (vm ) of less than 1 in an attempt to 

cut costs is undoubtedly a false economy, unless the 

only objective is the detection of large anomalies.

CONCLUSIONS AND RECOMMENDATIONS

The stream sediment experiment based on data 

from a stream drainage near Tracy Arm, southeastern Alaska, has pointed out some problems inherent 

in the standard reconnaissance geochemical survey. 

Most of these problems are related to the collection 

of a single sample at each location and the lack of 

replicate analyses. This 1x1 sampling design produces geochemical anomaly maps that are, in general, highly unstable. Information obtained from a 

geochemical survey can be maximized by careful consideration of the natural variations in samples and 

the expected analytical variation, and by the choice 

of a sample design that best fits these factors.

The following are some recommended procedures 

for reconnaissance stream-sediment surveys aimed 

at developing an understanding of background geochemistry and delimiting areas of anomalous metal 

concentrations:

1. A small-scale pilot study in the area to be surveyed is invaluable. A hierarchical-sampling 

design should be used and an analysis of variance should b© performed on the data to obtain 

variance components for each level of the sampling design, including the replicate-analysis 

level (Krumbein and Slack, 1956). This study 

will produce the best possible data for determining the sampling design for the major 

study.

2. If a pilot study is impossible, use the data generated by this study and others like it with 

extreme caution. The more an area differs from 

the area of this study in terms of terrain, 

climate, bedrock geology, and other factors, 

the less useful the specific data generated by 

this study are likely to be.

3. Set the spacing of sample locations on the basis 

of the variance components generated by the 

pilot study and the size of the smallest expected important anomaly.

4. Select a sampling design based on variance components and sample-collection and analytical 

costs. Use a sample design that keeps vm above 

1 for all major elements of interest. At this 

point, the total cost of the survey can be estimated and adjustments made to the spacing of 

sample locations and (or) the scope of the survey. For more help in establishing location 

spacing and calculating K, see Miesch (1976).

5. Before going into the field, prepare a detailed 

description of sampling procedures for each 

geologist. The target population being sampled 

should be identified, and procedures for randomly selecting samples at each location should 

be standardized.

6. If possible, use a randomizing technique when 

assigning numbers for analysis, and ship all 

samples for analysis to the laboratory at one 

time. Both procedures help to minimize variable bias (Miesch, 1976).

7. When plotting anomaly maps, plot location means 

only. Geometric means are more stable than 

arithmetic means.

8. When interpreting the anomaly maps, the most 

stable anomalies are those which involve more 

than one element over areas of at least several 

sample locations. Anomalies generated by only 

one element or at a single location should be 

considered suspect.

REFERENCES CITED

Brew, D. A., Grybeck, Donald, Johnson, B. R., Jachens, R. C., 

Nutt, C. J., Barnes, D. F., Kimball, A. L., Still, J. C., 

and Rataj, J. L., 1977, Mineral resources of the Tracy 

Arm-Fords Terror Wilderness Study Area and vicinity, 

Alaska: U.S. Geological Survey Open-File Report 77- 

649, 282 p.
EFFICIENT STREAM-SEDIMENT SAMPLING: AN EXPERIMENT AT TRACY ARM, ALASKA E9

Cochran, W. G., 1947, Some consequences when the assumptions for the analysis of variance are not satisfied: Biometrics, v. 3, no. 1, p. 22-38.

Eisenhart, Churchill, 1947, The assumptions underlying the 

analysis of variance: Biometrics, v. 3, no. 1, p. 1-21.

Grimes, D. J., and Marranzino, A. P., 1968, Direct-current 

arc and alternating-current spark emission spectrographic field methodis for the semiquantitative analysis 

of geologic materials: U.S. Geological Survey Circular 

591, 6 p.

Krumbein, W. C., and Graybill, F. A., 1965, An introduction 

to statistical models in geology: New York, McGraw-Hill, 

475 p.

Krumbein, W. C., and Slack, H. A., 1956, Statistical analysis 

of low-level radioactivity of Pennsylvanian black fissile 

shale in Illinois: Geological Society of America Bulletin, 

v. 67, p. 739-762.

Miesch, A. T., 1967, Methods of computation for estimating

geochemical abundance: U.S. Geological Survey Professional Paper 574-B, 15 p.

1976, Sampling designs for geochemical surveys—

Syllabus for a short course: U.S. Geological Survey 

Open-File Report 76-772, 140 p.

Motooka, J. M., and Grimes, D. J., 1976, Analytical precision 

of one-sixth order semiquantitative spectrographic analysis: U.S. Geological Survey Circular 738, 25 p.

Sower, F. B., Eicher, R. N., and Seiner, G. I., 1971, The 

STATPAC system: U.S. Geological Survey Computer 

Contribution no. 11, 36 p.

Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, 

Analytical methods used in geochemical exploration by 

the U.S. Geological Survey: U.S. Geological Survey Bulletin 1152, p. 92-94.

Ward, F. N., Nakagawa, H. M., Harms, T. F., and Van 

Sickle, G. H., 1969, Atomic absorption methods useful 

in geochemical exploration: U.S. Geological Survey Bulletin 1289, 45 p.

Indirect Determination of

Chloride in Plants by

Atomic-Absorption Spectrophotometry

By JOHN B. McHUGH and JAMES H. TURNER

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-F

A new rapid instrumental method 

for determining chloride 

in plant materials

CONTENTS

Page

Abstract _________________________________________ Fl

Introduction _____________________________-_____-____-____ 1

Acknowledgment ____________________________________________________ 1

Laboratory reagents and apparatus ____________________________________ 1

Procedure __________________________________________________________ 1

Sample preparation and determination _________________________________ 1

Standard preparation and calibration _________________________________ 2

Instrumentation ___________________________________________________ 2

Results ________ — ______________________________ 2

Discussion _________________________________________________________ 2

Precision _________________________________________________________ 2

Conclusion _________________________________________________________ 2

References cited _______________-______-___-____________-_--___--__--_---- 3

TABLES

Page

TABLE 1. A comparison of the chloride content of plant materials determined by the Mohr titrimetric method with

that determined by atomic-absorption methods _______________________________________________ F2

2. Repeatability of chloride-content determinations by atomic-absorption method _______________________ — _ 3

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

INDIRECT DETERMINATION OF CHLORIDE IN PLANTS BY 

ATOMIC-ABSORPTION SPECTROPHOTOMETRY

By JOHN B. McHuGH and JAMES H. TURNER

ABSTRACT

Chloride in plant materials is extracted by dilute nitric 

acid, and an appropriate aliquot of the acid solution is 

reacted with a known amount of standard silver-nitrate solution. The amount of chloride is calculated from the chloride 

equivalent of the difference in the amount of silver added 

and that remaining in solution after precipitation of silver 

chloride. The excess silver is determined by atomic-absorption spectrophotometry. The method is extremely fast with 

good precision and has a detection limit of 0.01 percent 

chloride in the bulk plant. The results compare favorably 

with those obtained by the Mohr titrimetric method.

INTRODUCTION

Atomic-absorption spectrophotometry offers a 

rapid, simple method for indirect determination of 

chloride in plants, whereas determining chloride by 

the classic Mohr titrimetric method entails a tedious sodium-carbonate fusion, a filtration, and a 

titration with a standardized silver-nitrate solution 

(Brown and others, 1970, p. 69). By using an adaptation of Ezell's method (Ezell, 1967), the amount 

of excess silver added to the sample is measured by 

atomic absorption, and the percent chloride is calculated from this measurement.

To determine chloride in plants by atomic-absorption spectrophotometry, the simple method described as follows is used: The sample is digested 

in 5 percent nitric acid, a known amount of standard 

silver-nitrate solution is added, chloride present is 

precipitated by the silver nitrate, and the excess 

silver is determined by the atomic absorption spectrophotometer. Slavin (1968, p. 158) reported that 

silver analyses is sensitive and interference free. 

Approximately 80 plant samples, against 20 for the 

Mohr method, can be determined per day by the 

atomic-absorption method.

ACKNOWLEDGMENT

Thanks are given to Helen L. Cannon, U.S. Geological Survey, Denver, Colo., for furnishing the 

samples used in these studies.

LABORATORY REAGENTS AND APPARATUS

All standards and reagents used in this method 

are stable and must be chloride free; the atomicabsorption silver standards, especially the lower 

ones, should be made up fresh every week. 

Standard silver solution, 1,000 jug/mL (micrograms 

per milliliter) : Dissolve 1.575 g reagent-grade 

silver nitrate in water; add 20 mL concentrated 

nitric acid; cool and dilute to 1,000 mL with demineralized water. Store in amber glass container.

Dilute standard silver solution, 100 ^g/mL: Dilute 

10.0 mL of the 1,000 jug/mL silver standard solution with 2 mL concentrated nitric acid and 

dilute to 100' mL with demineralized water. Store 

in amber glass container.

Nitric acid, concentrated, reagent-grade, chloridefree. 

Hotplate, oscillating: with temperature control from

90° to 370° C. 

Centrifuge, International Model K,1 variable speed

to 2,300 revolutions per minute. 

Atomic-absorption spectrophotometer.

PROCEDURE

SAMPLE PREPARATION AND DETERMINATION

Weigh a 1-g sample of oven-dried, ground plant 

material and transfer the sample to a 50-mL volu1 Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the 

U.S. Geological Survey.

Fl
F2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

metric flask; add 25 mL of 5 percent nitric acid to 

the sample ; place flask on a steam bath or hot plate ; 

and heat for 1 hour without boiling. Cool the solution and dilute to 50 mL with demineralized water, 

mix, and allow to stand until undigested sample 

settles out. Take an aliquot, usually from 25 to 0.5 

mL, depending on the chloride content of the sample, 

and transfer to a 100-mL volumetric flask ; then add 

sufficient deionized water to bring the volume to 40 

mL, and add 2 mL of concentrated nitric acid. Accurately measure 3.0 mL standard silver-nitrate 

solution, add to the sample solution, mix, and dilute 

to 100 mL with demineralized water. Place the solution in the dark until ready to be read on the atomicabsorption spectrophotometer. Mix the sample solution and transfer a portion to a 16x150 mm test 

tube and centrifuge for 15 min at 2,000 r/min. 

Measure the silver in the supernatant liquid on the 

atomic-absorption spectrophotometer.

STANDARD PREPARATION AND CALIBRATION

Working standards of 1, 5, 10, 20, and 30 

silver are made from 100 and 1,000 /*g/mL standard 

silver solutions. These working standards are made 

in 100-mL volumetric flasks by adding 1.0 mL, 5.0 

mL of the 100 /*g/mL stock solution and 1.0 mL, 

2.0 mL, 3.0 mL of the 1,000 ^g/mL stock solution to 

volume. All working standards for calibrating the 

atomic-absorption spectrophotometer are made up 

in 2 percent chloride-free nitric-acid solutions.

The optimum working range for silver is 2 to 20 

pg/mL (Perkin-Elmer Corp., 1968, p. Ag-1). Curvature correction technique (Perkin-Elmer Corp., 

1970, p. 2-8) is used to set working standards to a 

linear line on the Perkin-Elmer Model 403 atomicabsorption spectrophotometer.

INSTRUMENTATION

This work is performed on a Perkin-Elmer Model 

403 atomic-absorption spectrophotometer. Operating 

conditions used (Perkin-Elmer Corp., 1968, p. Ag-1) 

are listed as follows :

burner (4-inch flat head)

Perkin-Elmer silver hollow-cathode lamp operating at 12 mA (milliamperes)

wavelength =328.1 nm 

slit width = set at "4" (0.7 nm) 

acetylene = 34 flow-meter setting 

air = 64 flow-meter setting

RESULTS

Chloride percent is calculated on the basis of the 

chloride equivalent of the difference in silver added

and the amount remaining after precipitation. The 

following formula is employed to calculate the percent chloride by using this procedure:

Percent Cl~ = ((30.0 - 6) x 0.1643) /a, 

where

30.0 = /*g/mL silver added to the sample solution,

& = /Ag/mL silver remaining after precipitation, value obtained from atomic-absorption reading, 

0.1643 = chloride equivalent factor time dilution

factor, and 

a = aliquot taken.

DISCUSSION

An aliquot should be chosen that will consume a 

moderate amount (2 ^g/mL or more) of the silver 

added. With a high-chloride sample, use a small 

aliquot so that a sufficient amount of silver is left 

over to determine accurately; with a low-chloride 

sample, use a large aliquot (as much as 25 mL), 

enabling a more accurate and sensitive measurement 

of the chloride content of the sample. Sensitivity of 

0.01 percent chloride can be measured by use of a 

25-mL aliquot.

PRECISION

Table 1 shows the arithmetic mean of five determinations per sample, comparing the Mohr titration 

method with the atomic-absorption method. The 

plant material Bebbia juncea was from Death Valley, Calif.; all other plant materials were from 

Nevada. Table 2 shows the repeatability of the five 

plant samples by atomic-absorption spectrophotometry.

CONCLUSION

The atomic-absorption method offers a fast, 

simple, accurate way to analyze for chlorides in

TABLE 1.—A comparison of the chloride content of plant materials determined by the Mohr titrimetric method with 

that determined by atomic-absorption methods

Chloride (percent)

Sample 

Number DMaterial

Mohr

Atomic 

absorption

403648 

408134 

411477 

411478

412069

Sarcobatus vermiculatus 

Atriplex confertifoliaBaccharis glutinosa ——

0.63

1.90 

8.57 

.06 

4.84

0.52

1.65 

8.08 

.09 

4.28
DETERMINATION OF CHLORIDE IN PLANTS BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY F3

TABLE 2. — Repeatability of chloride-content determinations 

by atomic-absorption method

Sample Range of values Standard Relative stanNumber D- (percent) deviation dard deviation

403648 0.50-0.54 0.017 3.2 

408134 1.62-1.68 .022 1.4 

411477 7.97-8.22 .094 1.2 

411478 0.08-0.11 .016 17.7 

412069 4.05-4.40 .143 3.3

plant materials. With the exception of low-chloride 

samples, the reproducibility of the atomic-absorption 

method is good (table 2) . Five to 10 times as many 

samples per day can be determined by the atomicabsorption method as by the Mohr method. Indirect 

determination of chloride by atomic-absorption spectrophotometry in plant materials is a useful new 

method.

Brown, 

Mt 

foi

ve] 

5,

Ezell, J 

in 

no

Perkinab

Eh

SOI

Eli

Slavin, 

Yo

REFERENCES CITED

Brown, Eugene, Skougstad, M. W., and Fishman, M. J., 1970, 

Methods for collection and analysis of water samples 

for dissolved minerals and gases: U.S. Geological Survey Techniques of Water-Resources Investigations, book 

5, chap. Al, 160 p.

Ezell, J. B., Jr., 1967, Atomic absorption analysis of chloride 

in plant liquors: Atomic Absorption Newsletter, v. 6, 

no. 4, p. 84-85.

Perkin-Elmer Corp., 1968, Analytical methods for atomic 

absorption spectrophotometry: Norwalk, Conn., PerkinElmer Corp., 522 p.

1970, Instruction manual for Model 403 atomic absorption spectrophotometer: Norwalk, Conn., PerkinElmer Corp., pages unknown.

Slavin, Walter, 1968, Atomic absorption spectroscopy: New 

York, John Wiley, 307 p.

Determination of Iridium and Ruthenium

in Geological Samples by

Fire Assay and Emission Spectrography

^JOSEPH HAFFTY, A. W. HAUBERT, and N. J. PAGE

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-G

Detailed description of a method for determining 

trace amounts of indium and ruthenium

CONTENTS

Page

Abstract ______________________________________________ Gl

Introduction _____________________________________________________________ 1

Experimental method ____________________________________________________ 1

Fire assay ____________________________________________________________ 1

Spectrographic analysis _______________________________________________ 2

Preparation of standards ______________________________________________ 3

Results and discussion ____________________________________________________ 3

Precision and accuracy __________________________________________________ 3

References cited __________________________________________________________ 4

TABLES

Page

TABLE 1. Apparatus and spectrographic operating conditions for the determination of iridium and ruthenium ____ G2

2. Iron lines used for plate calibration __________________________________________________ 2

3. Analytical lines used in determination of iridium and ruthenium _______________________________________ 2

4. Comparison of iridium and ruthenium values obtained by this method with those quoted in the literature 4

5. Precision of the Ir-Ru method ______________________________________________________________________ 4

ill

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

DETERMINATION OF IRIDIUM AND RUTHENIUM IN GEOLOGICAL SAMPLES 

BY FIRE ASSAY AND EMMISSION SPECTROGRAPHY

By JOSEPH HAFFTY, A. W. HAUBERT, and N. J. PAGE

ABSTRACT

Microgram quantities of iridium and ruthenium are determined in geological materials by a combination fireassay and emission-spectrographic method. The method described is rapid and convenient as compared with other 

methods applied to these two metals. As little a,s 0.5 micrograms (fj.g) iridium and 1.5 ^g ruthenium can be detected. 

Based on a 15-g sample, this represents about 0.030 parts per 

million (ppm) iridium and 0.1 ppm ruthenium.

INTRODUCTION

Iridium, ruthenium, and osmium occur as alloys 

in alluvial and eluvial placer deposits, but knowledge 

of the residence and geochemical cycle of these elements in the parent rocks is poorly understood because of the lack of techniques to analyze rapidly 

large numbers of rock samples for these metals. 

Fewer analyses of Ru in rocks are available in the 

literature than are those for Ir and Os. For this 

reason, less is known about ruthenium's distribution 

in geologic materials and thus about its geochemical 

significance. The placer deposits of Ir, Ru, and Os 

appear to be derived from alpine-type ultramafic 

and mafic rocks (ophiolitic sequences), whereas Pd 

and Pt placer deposits appear to originate from 

stratiform and concentrically zoned ultramafic and 

mafic complexes. Evidence for the different geochemical behavior for the two groups of platinumgroup metals was reported by Cabri and Harris 

(1975), who used the PtxlOO/(Pt+Ir+Os) ratios 

in concentrates from alluvial and eluvial deposits to 

relate deposits with low ratios to alpine-type parents 

and those with high ratios to stratiform and concentric environments. More recently, Rajamani and 

others (1977) demonstrated that Ir and Os are distributed differently than Pt and Pd in sulfide and 

basaltic melts and thus emphasized the need for

data on the distribution of these metals in geologic 

materials.

Methods for the determination of Ir and Ru using 

fire assay and Pt as a collector have been described 

(Broadhead and others, *1972; Page and others, 

1976; Haffty and others, 1977). The neutron-activation method described by J. J. Rowe in Page and 

others (1976) and by Haffty and others (1977), 

although more sensitive, is tedious and time consuming. This method is also subject to fission product 

interference from 103Ru produced from U, unless 

sample pretreatment consisting of separating the 

Ru as the tetroxide, as described by Koda (1970), 

is employed.

As more analytical techniques become available 

for determining Ir, Ru, and Os, we hope that the 

geochemistry of these three elements will become 

better understood and that exploration for possible 

lode deposits will be a reality. Although similar to 

the method reported by Broadhead and others, the 

method described here for the determination of Ir 

and Ru is, overall, more convenient to apply.

EXPERIMENTAL METHOD 

FIRE ASSAY

Ten milligrams of Pt (99.999 percent pure), in 

the form of 0.254-mm (0.01-in.) -diameter wire, is 

used as a collector for Ir and Ru. The wire is weighed 

to an accuracy of ±0.002 nig. A piece of lead foil 

20 mm by 13 mm and 0.2 mm thick is sharply 

folded lengthwise at the center with pliers. The fold 

is then opened, the platium wire placed in the center 

of the crease, and the fold closed on the wire and 

again folded lengthwise at the center to give a 

thickness of four layers. All edges are then crimped

Gl
G2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

with pliers to ensure enclosure of the wire. This 

lead envelope is added as the last step in the preparation of the fusion mixture.

The fusion mixture consists of a flux formed by 

combining Na2C03 , PbO, Si02 , Na2B4 07 , and CaF,, 

together with household flour as a reducing agent or 

KN(X as an oxidizing agent, depending on the chemical and mineralogical composition of the sample. 

These are combined in a "30-g" fire-clay crucible; 

15 g of sample is added, followed by the lead foil 

containing the platinum wire. The contents are 

thoroughly mixed, after which the crucible is placed 

in the muffle of an assay furnace preheated to a 

temperature of 1,000° C. The fusion and cupellation 

steps are described in detail by Haffty and others 

(1977). However, there is one modification to the 

cupellation step. After the buttons are "open," the 

temperature is decreased to 860° C, rather than 

840° C, and finished at 920° C. The platinum beads 

obtained after cupellation are weighed, and the increase in weight over that of the Pt added is noted.

SPECTROGRAPHIC ANALYSIS

The noble metals from 15 g of sample are contained in the platinum beads obtained after cupellation. The beads are transferred to cupped graphite 

electrodes. The sample-bearing electrodes are then 

placed in the arc-spark stand, the beads are excited, 

and the spectra are recorded using the apparatus 

and operating conditions listed in table 1.

The emulsion is calibrated by means of an iron 

bead arced at 5.5 A dc and exposed for 25 s at a 

transmission of 25 percent. The iron lines and relaTABLE 1.—Apparatus and spectrographic operating conditions 

for the determination of iridium and ruthenium

Excitation source __dc arc at 300 V (open circuit) and 20 A.

Electrodes ________Anode: 3.2-mm (0.125-in.) -diameter

graphite with 6.35-mm (0.25-in.) -deep 

cup, Ultra Carbon1 stock no. 213202. 

Cathode: ASTM type C-l, Ultra Carbon 

stock no. 111202.

Spectrograph ————Jarrell-Ash 3.4-m, Wadsworth mounted 

grating with 5,906 grooves per centimeter (15,000 grooves per inch), giving 

a reciprocal linear dispersion of 0.524 

nm/mm in the first order.

Wavelength region -225-350 nm.

Slit width ______15 /*•

Illumination _______ Arc image focused on grating.

Analytical gap _____4 mm, maintained during burn.

Transmission ____40 percent.

Exposure _______40 s.

Emulsion ______Kodak SA-1.

1 Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the U.S. 

Geological Survey.

TABLE 2.—Iron lines used for plate calibration

Fe line 

(nm)

315.789

317-5^5

317.802

319.693

320.5^0

321.59^

Intensity

73

125

9>*

1*70

210

225

Fe line 

(nm)

321.738

322.207

322.599

323.9^^

325. 12U

326. 82U

Intensity

165

625

770

285

62

29

tive intensities used for plate calibration were selected from a list of homologous lines (Crosswhite, 

1950; Bastron and others, 1960) and are reproduced 

in table 2 for the convenience of the reader. The 

calibration curve is established by plotting transmission (ordinate) versus intensity (abscissa) on 

log-log paper.

The spectra of standards and unknown samples 

are recorded on separate photographic plates. The 

iron bead spectrum, which is used for plate calibration, is always put on the unknown-sample plate. 

After the plates have been processed, transmittance 

measurements of selected analytical and internal 

standard lines (table 3) are obtained by means of a 

microphotometer. From the calibration curve, intensity values are obtained for the standards and 

are used in constructing the analytical curves. Once 

the transmittance values for the standards are 

established, they are used repeatedly for obtaining 

the intensities from succeeding calibration curves 

for plates bearing the unknown samples. The analytical curves are established by plotting the ratio of 

the intensities of the analytical and internal standard lines against concentration, in micrograms, on 

logarithmic coordinates. The concentration of the 

elements in the unknown samples are read from the 

analytical curves. This concentration, in micrograms, is then divided by the weight of sample 

taken to give parts per million or parts per billion 

(10~ 9 ) in the sample.

TABLE 3.—Analytical lines used in determination of iridium 

and ruthenium

[The Pt 27^.1*83-nm line was used as internal standard line 

throughout]

Element 1

Iridium ——————

Analytical Line 

(nm)

281;. 973 

292.VT9 

295.126

C- | _J • ,/ | C.

287.1*98

Concentration range 

(vg)

0.5- 25 

0.5- 25 

15 -100

2.5-100 

1.5- 50
DETERMINATION OF IRIDIUM AND RUTHENIUM BY FIRE ASSAY, EMISSION SPECTROGRAPHY G3

PREPARATION OF STANDARDS

Two sets of standards are prepared. One set is 

made using measured volumes of single-metal standard solutions containing 1,000, 100, 10, and 1 ppm in 

2 M HC1. These standard solutions are made by 

serially diluting standard stock solutions calculated 

to contain 1,000 mg of the element per liter. The 

stock solutions are prepared by dissolving 229.5 mg 

of spectrographic grade ammonium chloroiridate 

((NH4 ) 2 IrCl 6 ) and 328.8 mg of ammonium aquochlororuthenite ((NH4 ) 2Ru(H2O)Cl5 ) in 100-mL 

volumetric flasks and diluting to volume with 2 M 

HC1.

Micropipettes, used to measure the volumes of the 

standard solutions, are selected to give 1001 , 50, 25, 

10, 5, 2.5, 1.0, 0.5, and 0.25 /*g of Ir and Ru in solution. Thirty grams Na2CO;! , 50 g PbO, and 15 g SiO2 

(used as sample blank) are weighed in that order 

into each of nine fire-clay crucibles. The standard 

solutions are transferred carefully to the top of the 

SiO2 , so that the solutions are kept away from the 

crucible walls. The solutions are dried by placing the 

crucibles under heat lamps for several hours. Then, 

5 g Na 2B4 O7 , 1 g CaF2 , 3.0 g of household flour, and 

10 mg of pure Pt (used as a collector, as in the 

samples) are added to complete the charge. The 

contents are mixed and then fused. The buttons are 

cupelled and the beads arced as described previously.

The second set of standards is prepared by using 

various weights of 0.025-mm (0.001-in.) -diameter 

wire consisting of 10 percent Ir and 90 percent Pt. 

The wire is cut in predetermined lengths and accurately weighed on a Cahn electrobalance. Then the 

pieces of wire are transferred from the weighing 

pan to lead foil for convenience of handling, as described previously for platinum wire. The weights of 

Ir are selected to approximate, as closely as possible, 

those weights obtained using the reciprocal of the 

cube root of 10 (0.4642) as a dilution factor, resulting in a 3-step breakdown per order of magnitude. 

The actual weights of Ir obtained were 0.34, 0.52, 

1.22, 2.53, 5.34, 12.19, 21.13, 50.92, and 105.6 /*g.

Ruthenium alloyed with platinum (5 percent Ru 

and 95 percent Pt), in the form of wire 0.127 mm 

(0.005 in.) in diameter, is also added to this second 

set of standards in varying weights as described for 

Ir. These Ir-Pt and Ru-Pt weighed pieces of wire are 

added to blank fire-assay charges along with pure 

Pt as a collector—taking into account the weight 

of Pt contributed by both the Ir-Pt and Ru-Pt wire. 

The charges are processed and the beads arced as 

described previously.

RESULTS AND DISCUSSION

Although this method is similar to that of Broadhead and others (1972), it varies in significant particulars so that the method described here is more 

convenient to apply. For example, the Pt, which is 

used as a collector for Ir and Ru, is introduced in the 

form of pure wire rather than by adding specific 

amounts of platinum stock solution to the fire-assay 

charge and waiting for the charge to dry overnight. 

Many pieces of wire can be cut beforehand and made 

available, particularly if many samples are to be 

analyzed for these two metals. The use of radiotracers or yield-correction factors was found to be 

unnecessary if the standards were treated in the 

same way as the unknown samples. In addition, as a 

result of the standards being exposed on a separate 

photographic plate, the standards need only be prepared and excited occasionally. Having once obtained 

the transmittance values for the analytical lines, 

these values can be used repeatedly for obtaining the 

intensities from succeeding calibration curves established for unkown-sample plates.

Two sets of standards—one set using standard 

solutions, the other using Ir-Pt and Ru-Pt wire— 

were used in obtaining the data in table 4. When 

compared with the literature values for both Ir and 

Ru, the values obtained using solution and wire 

standards are both seen to be within acceptable 

limits. However, standard solutions are preferred 

for analysis because they are more convenient to 

prepare. In another study, known amounts of Ir-Pt 

and Ru-Pt wire were added to a flux contained in a 

fire-clay crucible and run as unknown samples; favorable results were obtained for both elements using 

either set of standards. This demonstrates that when 

Ir and Ru are present as an alloy, acceptable results 

can be obtained. Thus, it appears that the method is 

not significantly affected by the chemical form in 

which Ir and Ru exist in geological samples.

PRECISION AND ACCURACY

The precision of the method is illustrated by the 

results shown in table 5. The standard deviations 

were obtained by running eight 15-g portions of the 

South African reference sample. Standard deviations for iridium and ruthenium using both solution 

and wire standards are comparable.

A measure of the accuracy is obtained by comparing the values obtained by this method with those 

obtained using other techniques (table 4), namely, 

atomic-absorption spectroscopy, optical emission 

spectrography, and neutron-activation analysis.
G4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 4.—Comparison of iridium and ruthenium values obtained by this method ivith those quoted in the literature

[Data are in parts per million. For samples run more than once, values shown are averages.

All samples weighed 15 g]

This method

Sample Sample 

runs

Merensky Reef 

reference E 

(South Afri 

Rustenburg Pi 

(South Afri 

H chromitite 

J chromitite 

A chromitite 

A chromitite

* ore, 

sample,

; ore

(20MV68)- 

(HBE68) — 

(8WF68)— 

(13WF68)-

8 

2

1 

1 

1 

1

Solution standards

Ir

0.086

.11 

.025 

.089 

.6k 

.13

Ru

0.1*5

.56 

.15 

.59 

.91 

.35

Wire standards

Ir

0.083

.11 

.015 

.085 

.61

.12

Ru

o.Ho

• 50

.17 

• 53 

.81 

.31

Literature Values

Ir

0.01k

.Ik 

.030 

.086 

.530 

.170

Ru

O.k3

.61 

.232 

.U82 

.900 

.270

Source

Steele and others (1975).

Broadhead and others (1972). 

Page and others (1976). 

Do. 

Do. 

Do.

TABLE 5.—Precision of the Ir-Ru method

[(S) = by solution standards; (W) = by wire standards; n =

Element

Ruthenium (S) — - 

Ruthenium (W) ——

Average 

Concentration 

(ppm)

0.086 

.083

A5

.ko

Standard 

deviation 1

0.0070

.0065

.069 

.061

Coefficient 

of variation2

8.1 

7.8

15 

15

/£ j2

1 Standard deviation = /———- where n is the number of 

v n - 1

individual results, and d is the difference between individual 

results and their average.

Standard deviation x 1QQ___ 

average of individual results Coefficient of variation =

REFERENCES CITED

Bastron, Harry, Barnett, P. R., and Murata, K. J., 1960, 

Method for the quantitative spectrochemical analysis of 

rocks, minerals, ores, and other materials by a powder 

d-c arc technique: U.S. Geological Survey Bulletin 1084- 

G, p. 165-182.

Broadhead, K. G., Piper, B. C., and Heady, H. H., 1972, Fire 

assay-emission spectrographic determination of iridium, 

ruthenium, and osmium: Applied Spectroscopy, v. 26, no. 

4, p. 461-467.

Cabri, L. J., and Harris, D. C., 1975, Zoning in Os-Ir alloys 

and the relation of the geological and tectonic environment of the source rocks to the bulk Pt:Pt+Ir+Os 

ratio for placers: Canadian Mineralogist, v. 13 p. 266- 

274.

Crosswhite, H. M., 1950, Photoelectric intensity measurements in the iron arc: Spectrochimica Acta, v. 4, p. 

122-151.

Haffty, Joseph, Riley, L. B., and Goss, W. D., 1977, A manual 

on fire assaying and determination of the noble metals in 

geological materials: U.S. Geological Survey Bulletin 

1445, 58 p.

Koda, Y., 1970, Determination of radio ruthenium using a 

polyethylene film: Journal of Radioanalytical Chemistry, 

v. 6, p. 345-357.

Page, N. J., Rowe, J. J., and Haffty, Joseph, 1976, Platinum 

metals in the Stillwater Complex, Montana: Economic 

Geology, v. 71, p. 1352-1363.

Rajamani, V., Chou, C. L., and Naldrett, A. J., 1977, Partitioning of Pt-group elements between sulfide and basaltic 

melts [abs.] : Geological Society of America Abstracts 

with Programs, v. 9, no. 7, p. 1135-1136.

Steele, T. W., Levin J. Copelowitz I., 1975, The preparation 

and certification of a reference sample of a preciousmetal ore: Johannesburg, South Africa, National Institute for Metallurgy, report no. 1696, 50 p.
Complexity of Titaniferous Magnetites 

from Essex County, New York, as a 

Hindrance to Beneficiation by a Method 

Based on Curie Temperature Differences

By HARRY KLEMIC and PATRICIA J. LOFERSKI

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-H

The compositions of some titaniferous magnetite 

concentrates separated magnetically at high 

temperatures are presented

CONTENTS

Page

Abstract __________________________________________— HI

Introduction ______________________________________ 1

Characteristics of source materials ________________________________ 1

Magnetic properties __________________________________—_____ 2

Sample preparation and separation procedures ______________________—_____ 4

Results of high-temperature magnetic tests ______________ — __——___ 4

Conclusions __________________________________________ 5

References cited _________________________________———__ 5

ILLUSTRATION

Page

FIGURE 1. Curie points of minerals in magnetite-ulvospinel series and in hematite-ilmenite series ____—__—___ H3

TABLES

Page

TABLE 1. Spectrographic analyses of magnetite-ilmenite ore and magnetite concentrates from Essex County,

N.Y _____________________________________________________________________________________ H2

2. Range in composition of separates of heated magnetite concentrates from Little Pond deposit, Essex

County, N.Y _______________________.______________________________ 5

3. Partial results of spectrographic analyses of separates of heated magnetite concentrates from Little

Pond deposit, Essex County, N.Y _____________________—________—_—_____—_—___—_____ 5

in

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

COMPLEXITY OF TITANIFEROUS MAGNETITES FROM

ESSEX COUNTY, NEW YORK, AS A HINDRANCE TO BENEFICIATION BY 

A METHOD BASED ON CURIE TEMPERATURE DIFFERENCES

By HARRY KLEMIC and PATRICIA J. LOFERSKI

ABSTRACT

Titanium and some other elements that substitute for iron 

in magnetite lower the Curie temperature of the magnetite. 

We made high-temperature magnetic separations of magnetite concentrations from mineralogically complex magnetiteilmenite ores from the Little Pond and Sanford Lake deposits, Essex County, N.Y., in an attempt to obtain separates having different titanium contents. Finely ground 

samples of magnetite concentrates were heated to temperatures of 500° C and higher and were separated magnetically while hot by means of a hand magnet. The magnetic and 

nonmagnetic fractions obtained contained 3-4 percent 

titanium and lesser amounts of aluminum, magnesium, manganese, and vanadium as determined by spectrographic analysis. However, the magnetic and nonmagnetic separates 

were almost identical in composition.

We concluded that the magnetites from the Little Pond 

deposit are too complex in mineralogic association and composition to be beneficiated by the methods we used. We believe, however, that the method is worthy of testing where 

more refined equipment and techniques are used and that it 

may be applicable to the benefication of some titaniferous 

magnetites and other magnetic minerals.

INTRODUCTION

The high titanium content of the magnetite in 

ilmenite ores of Essex County, N.Y., is a detriment 

in smelting the magnetites for iron. Although the 

titanium content of the iron-rich part of the ores 

can be reduced by magnetic separation of most of 

the magnetite from the ilmenite, the magnetite concentrates still contain excessive amounts of titanium. Examinations of samples of ore-grade material 

from the Little Pond deposits have shown compositional variations in the magnetite.

Titanium and some other elements that substitute 

for iron in magnetite serve to lower the Curie temperature below that of pure magnetite. Ideally, this 

effect might be used to advantage in the beneficiation

of titaniferous magnetite. It should be possible to 

separate titaniferous magnetite concentrates into 

fractions having different amounts of titanium by 

heating the magnetite concentrate feed to above the 

Curie temperature of part of the material, which 

will render that part nonmagnetic, and by performing a magnetic separation of the heated material.

We have tried such a method on material from 

the Little Pond and Sanford Lake deposits. Although separations of heated material into magnetic 

and nonmagnetic fractions were obtained well below 

the Curie temperature of pure magnetite, the compositions of separates of Little Pond material were 

almost identical, as determined by spectrographic 

analyses. We consider the results of the tests of the 

Little Pond material to be unsatisfactory. A sample 

of Sanford Lake magnetite concentrate tested at a 

furnace temperature of 500° C was nonmagnetic. 

No further tests or analyses of this material were 

made.

CHARACTERISTICS OF SOURCE MATERIALS

The magnetite-ilmenite ores of Essex County are 

mineralogically complex. The Little Pond ores occur 

in gabbro, and they contain gangue minerals such 

as plagioclase, pyroxene, hornblende, olivine, spinel, 

and garnet. Most magnetite grains in the ore-grade 

material are less than 3 mm in diameter, and many 

grains contain blebs and exsolution lamellae of 

gangue minerals. The magnetite also contains titanium and other impurity elements in solid solution.

Chemical analyses of the Little Pond magnetite 

ores reported by Kemp (1899) showed about 8 and 

11 percent titanium in two samples. Spectrographic 

analyses by J. L. Harris and Leung Mei of the U.S.

Hi
H2 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 1.—Spectrographic analyses of magnetite-ilmenite 

ore and magnetite concentrates from Essex County, N.Y.

[Analyses by J. L. Harris and Leung Mei, U.S. Geological Survey. Elements looked for, but below minimum limits assigned for method used, 

are: As, Au, B, Be, Cd, Ce, Cu, Dy, Er, Eu, Gd, Ge, Hf, Ho, In, Ir, La, 

Lu, Nd, Os, Pd, Pr, Pt, Re, Rh, Sb, Sm, Ta, Tb, Tl, Tm, U, and 

W. H was not determined because of interference. The standard deviation of any single result should be taken as +50 percent and —33 

percent]

Element

Little Pond 

Magnetite-ilmenite

ore, sample No.

74Jy23-2, lab. No.

W-187770, sample

spectrum

Sanford Lake 

Magnetite concentrate, sample No. 

HKSL-M, lab. No. 

W-192907, sample 

spectrum

Percent

Si __________ 3.6 3.3

Al __________ 2.8 1.8

Fe __________ >24 >24

Mg _________ 4.6 0.59

Ca __________ 0.83 0.12

Na _________ 0.1 0.007

K ___________ H H

Li ___________ H H

Ti __________ 5.3 3.4

P __________ <0.07 <0.07

Mn _________ 0.33 0.13

Parts per million

Ag __________ 0.5 0.97

Ba _______—— 17 9.7

Co ___________ 169 110

Cr __________ >6,80'0 1300

Ga __________ 64 110

Mn _________ 3,270 1,300

Mo _________ <2.1 12

Nb _________ 21 <22

Ni __________ 420 180

Pb __________ 50 62

Pr __________ 34 68

Sc __________ 13 9.5

Sn __________ <14.7 41

Sr __________ 17 3.2

V__________ >1,000 x 1,500

Y __________ 9.6 23

Yb ________ 1.9 2.9

Zn __________ 580 650

Zr __________ 59 68

1 Visual reading of plate.

Geological Survey in studies made for this report 

show 5.3 and about 6 percent titanium in two oregrade samples. The results of these analyses and of 

an analysis of magnetite concentrate from the Sanford Lake deposits are shown in table 1.

The ilmenite-magnetite ores of the Sanford Lake 

deposits include two major types: anorthositic ore 

having a ratio of total Fe:Ti02 of greater than 2:1, 

and gabbroic ore having a ratio of total Fe:Ti02 of 

less than 2:1 (Gross, 1968; Kays, 1961). Granular 

magnetite and ilmenite occur together in the ores 

and are commonly coarse grained. The magnetite 

generally contains exsolution laths and blebs of 

titanium-bearing minerals, including ilmenite, 

rutile, ulvospinel, hercynite, and possibly coulsonite 

(FeV2 04 ). Some vanadium may also be in the magnetite lattice (Balsley, 1943; Gross, 1968). As much

as 35 percent of the volume of some magnetite 

grains consist of ilmenite intergrowths (Stephenson, 1945).

As shown in the results of the spectrographic 

analyses, the Little Pond ore specimen contains 

more magnesium, aluminum, calcium, silicon, and 

titanium than does the Sanford Lake concentrate, 

probably because of the presence of more of the 

gangue minerals in the ore.

Although some of the titanium in both samples is 

in ilmenite, which is mostly in discrete grains in the 

Little Pond specimen and in exsolution laths in the 

Sanford Lake magnetite concentrate, some of the 

titanium is in the magnetite. Electron microprobe 

studies of the Little Pond magnetite (Bird and 

Klemic, 1976) revealed compositional variations both 

within single grains and between different magnetite grains. The material was analyzed for eight 

elements: Fe, Ti, Al, Mg, Mn, Si, V, and Cr. Major 

variations were noted for Ti (4.5-13.4 percent) and 

Al (1.01-5.2 percent). Variations for the less 

abundant elements were also noted.

Because of these compositional variations, we inferred that in grinding the grains to finer particle 

sizes, the fine particles would have a spectrum of 

compositions and that they would have a related 

spectrum of Curie temperatures.

MAGNETIC PROPERTIES

The principal oxide minerals that are commonly 

present in titaniferous iron deposits are magnetite 

(Fe3 04 ) and ilmenite (FeTi03 ). Maghemite 

(Fe2 03 ), ulvospinel (Fe2Ti04 ), and hematite 

(Fe2 03 ) may also be present. Magnetite and ulvospinel form a compositional series, and hematite and 

ilmenite form another compositional series. In 

major titaniferous magnetite deposits, the bulk of 

the magnetite is nearer in composition to the magnetite end member than to ulvospinel, and the bulk 

of the ilmenite is nearer in composition to the 

ilmenite end member than to hematite. The magnetic susceptibilities of these two minerals differ 

considerably at room temperature.

The temperatures above which the minerals of the 

magnetite-ulvospinel series and the ilmenite-hematite series are nonmagnetic (Curie points) are 

shown in figure 1. The curves in figure 1 are based 

on data reported by Syono (1965, p. 79, fig. 2) and 

Stacey and Banerjee (1974, p. 37) and are in part 

from earlier reports by Akimoto (1962), Ishikawa 

and Akimoto (1958), Nagata and Akimoto (1956), 

and Bozorth and others (1957).
COMPLEXITY OF MAGNETITES, ESSEX COUNTY, N.Y., A HINDRANCE TO BENEFICIATION H3

700

PERCENT Ti

F6203 (hematite) (ilmenite) FeTi03

0 3.15 6.3 9.45 12.6 15.15 18.9 22.05 25.2 28.35 31.5

600

500

400

g 300

3

200

100

-100

\

\

\

\

\

\

\

\ xHematite-ilmenite series 

\

Magnetite-ulvospinel series

0 2.14 4.29 

FeaOa (magnetite)

6.43 8.57 10.72 12.86 

PERCENT Ti

15.0 17.14 19.29 

(ulvospinel)

21.43

FIGURE 1.—Curie points of minerals in magnetite-ulvospinel series and in hematite-ilmenite series. Different temperature have been reported by different authors for magnetites near the upper part of the curve.
H4 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

In both series, the Curie temperatures decrease 

as titanium content increases. Magnetite from the 

deposits of interest to us in this study probably 

contains less than 25 percent of the ulvospinel in 

solid solution (about 5 percent Ti) ; therefore, 

the Curie points of the magnetite should be higher 

than 430° C.

SAMPLE PREPARATION AND SEPARATION 

PROCEDURES

The Little Pond "ore" was crushed and ground, 

and the Sanford Lake magnetite concentrate was 

also ground. Both samples were sieved, and the 

fractions between 170- and 325-mesh sizes were 

selected for tests. These samples were repeatedly 

separated magnetically by a hand magnet to eliminate nonmagnetic minerals. Some of the material 

was ground to minus 325-mesh size and again separated magnetically. X-ray analyses indicated that a 

small amount of ilmenite, probably less than 5 percent, was still present in the magnetic samples.

After some preliminary trials in which we noted 

problems related to cooling of the samples during 

separation tests and other undesired effects, we decided to use Pyrex1 test tubes as sample holders. 

The samples were spread thinly in the test tubes, 

which were laid on their sides in grooves on pieces 

of insulation bricks in an electric furnace. The furnace was heated to desired temperatures for the different test runs. Prior to removal of the tubes from 

the furnace for magnetic tests, the tubes were tapped and rolled to reduce the sintering effect of 

heating. Some magnetic tests were made while the 

tubes were inside the furnace but near the mouth 

of the furnace. In other tests, the test tubes and the 

pieces of insulation bricks were removed from the 

furnace for convenience of handling. The heat of 

the enclosing tubes tended to reduce the rate of 

cooling of the samples during the time necessary to 

make the magnetic separations.

The use of the tubes as sample holders also made 

it possible to maintain fairly uniform distances between the magnet and the hot samples. The magnet 

was placed against the upper side of the sample 

tube and moved along the length over which the 

sample was spread. Any material that had retained 

its magnetism at the test temperature was attracted 

to the upper side of the tube and was drawn along 

the tube to a separate place and dropped by removal of the magnet. The magnet was again placed

1 Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the 

U.S. Geological Survey.

above the remaining nonmagnetic part of the hot 

sample. As the sample cooled, it recovered its magnetism, and the time lag for recovery could be noted.

RESULTS OF HIGH-TEMPERATURE 

MAGNETIC TESTS

After a few tests using the Pyrex tubes as sample 

holders, we concluded that placing the samples in 

the preheated furnace at temperatures of 410° C 

or more and heating to higher temperatures in runs 

of less than an hour duration gave desired results 

in the altering of part of the material to a nonmagnetic state. Nonmagnetic material was present in 

all but one of the Little Pond samples tested magnetically at a furnace temperature of 500° C or 

higher, but that one sample may not have reached 

furnace temperature before the magnetic test was 

made. In some of the tests, the amount of nonmagnetic material was greater than the amount of 

material that retained its magnetism at the test 

temperatures.

Only one test was performed on Sanford Lake 

material after the preliminary tests. That sample, 

tested at 500° C, was nonmagnetic.

Magnetic and nonmagnetic separates obtained 

from Little Pond "ore" in separations made ait furnace temperatures of 520° C were analyzed by X-ray 

diffraction, primarily to compare their ilmenite contents. In two pairs of separates, no obvious difference in their ilmenite contents was found. In one 

other pair of separates, the nonmagnetic fraction 

contained slightly more ilmenite.

The results of the magnetic tests show that parts 

of the Little Pond concentrates became nonmagnetic at 500° C, and other parts remained magnetic 

at 540° C, the highest furnace temperature used in 

the final tests.

Magnetic and nonmagnetic fractions of Little 

Pond concentrates from four heating runs were 

analyzed spectrographically by J. L. Harris, of the 

U. S. Geological Survey. The ranges, reported in 

abundance of 19 elements that were present in most 

of the fractions, are shown in table 2. The Sanford 

Lake separates were not analyzed spectrographically after heating.

The amounts of the more abundant elements that 

are likely to proxy for iron in magnetite in each of 

the separates, as determined by spectrographic analysis, are shown in table 3 for convenience of comparison. These elements are titanium, aluminum, 

magnesium, manganese, and vanadium. The standard deviation of +50 percent and —30 percent of
COMPLEXITY OF MAGNETITES, ESSEX COUNTY, N.Y., A HINDRANCE TO BENEFICIATION H5

TABLE 2.—Range in composition of separates of heated magnetite concentrates from Little Pond deposit, Essex County, 

N.Y., as determined by spectrographic analyses

[Analyst: J. L. Harris, U.S. Geological Survey. Other elements looked for 

but below minimum limits assigned for method used are Ag, As. Au 

B, Ba, Be, Bi, Cd, Ce, Dy, Er, Eu, Gd, Ge, Hf, Ho, In, Ir, La, Lu, Mo, 

Nb, Nd, Os, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sm, Sn, Ta, Tb, Te, Th, Tl, 

Tm, U, W, Y, and Yb. The standard deviation of any single result 

should be taken as +50 percent and —33 percent]

Element

Ti

Al __ _ Mg _

Mn _ __

Si _ ____

Fe ___ _ _

Ca __

Na __ _

V 1 ______ Cr 1

Range, 

in percent

2.88 4.18

1.66-2.48

1.40-1.91

.30- .36

2.50-3.73

>23.5

.67 .85

.02- .05

.15- .3

about 1

Element

Co

Pn

Ga _______

Ni _ _ _

Pb _______

Op

er

Zn

rj-f

K __ _ _

Range, 

in parts 

per million

127 -155

29.2- 62.2

48.5 75.2

309 -400

110 -154

71 — Q 0

8 7 17

452 -643

54 - 74

1 Visual reading of plate.

the amounts reported for elements analyzed by the 

spectrographic method greatly exceeds the reported 

differences in compositions.

CONCLUSIONS

On the basis of our tests and the analytical results, we believe that the titaniferous magnetite of 

the Little Pond deposit is too complex, both in composition and in content of gangue minerals in the 

form of exsolution lamellae and minute blebs, to be 

beneficiated by magnetic separations made on the 

basis of differences in Curie temperatures.

We believe, however, that the method of mineral 

separation based on Curie temperature differences 

is worthy of further testing. The construction and 

development of a magnetic separator for operation 

at controlled temperatures and through a broad 

range of magnetic intensities may make it possible 

to separate not only titaniferous magnetites but also 

other more weakly magnetic minerals that are difficult to separate at ordinary temperatures. Success 

in the application of this method to mineralogically 

complex magnetite concentrates may depend on the 

use of very fine particle sizes.

REFERENCES CITED

Akimoto, Syuniti, 1962, Magnetic properties of FeO-Fe2O^- 

Ti02 system as a basijs for rock magnetism: Physics 

Society of Japan Journal, v. 17 (supp. B-I), 706 p.

Balsley, J. R., Jr., 1943, Vanadium-bearing magnetite-ilmenite 

deposits near Lake Sanford, Essex County, New York: 

U.S. Geological Survey Bulletin 940-D, p. D99-D123.

Bird, M. L., and Klemic, Harry, 1976, Vanadium, manganese, 

chromium, magnesium, and aluminum in minerals of 

some magnetite-ilmenite deposits of the eastern Adirondacks [abs.] : Geological Society of America Abstracts 

with Programs, v. 8, no. 2, p. 134.

Bozorth, R. M., Walsh, D. E., and Williams, A. J., 1957, 

Magnetization of ilmenite-hematite system at low temperatures: Physical Review, v. 108, no. 1, p. 108-157.

Gross, S. 0., 1968, Titaniferous ores of the Lake Sanford 

district, New York, in One deposits of the United States, 

1933-1967 (Graton-Sales volume), v. 1: New York, 

American Institute of Mining, Metallurgical, and Petroleum Engineers, p. 140^153.

Ishikawa, Yokichi, and Akimoto, Syuniti, 1958, Magnetic 

property and crystal chemistry of ilmenite (FeTi03) and 

hematite (Fet>03 ) system, 2, magnetic property: Physics 

Society of Japan Journal, v. 13, p. 1298.

Kays, M. A., 1961, Petrography of the Sanford Hill titaniferous magnetite deposit, Essex County, New York: St. 

Louis, Mo., Washington Univ., Ph. D. thesis, 127 p.

Kemp, J. F., 1899, Titaniferous iron ores of the Adirondacks: 

U.S. Geological Survey 19th Annual Report, pt. 3, p. 

377-422.

Nagata, Takesi, and Akimoto, Syuniti, 1956, Magnetic properties of ferromagnetic ilmenites: Milan, Geofisica Pura 

e Applicata, v. 34, p. 36.

Stacey, F. D., and Banerjee, S. K., 1974, The physical principles of rock magnetism: New York, Elsevier Scientific 

Publishing Co., Development of Solid Earth Geophysics, 

no. 5, 195 p.

TABLE 3.—Partial results of spectrographic analyses of separates of heated magnetite concentrates from Little Pond deposit, Essex County, N.Y.

[Analyst: J. L. Harris, U.S. Geological Survey. Results are in percent. Chromium estimated to be about 1 percent in all separates by visual examination of spectrographic plate. Vanadium content estimated by visual examination of spectrographic plate. The standard deviation of any single 

result should be taken as +50 percent and — 33 percent, mg, magnetic; nmg, not magnetic

Element

Ti _ _ _ _

Al __ _ __

Mg ____________

Mn __ _ _ __

V ___ __

A 

mg

3.1 

2.0 

1.7 

0.3 

0.3

Run 8

B

nmg

3.6 

2.3 

1.8 

.4 

0.2

Run 11

C

nmg

3.7 

2.4 

1.7 

.4 

0.2

D 

mg

4.1 

2.2 

1.9 

.3 

.2

E

nmg

2.9 

2.5 

1.8 

.4 

.2

F 

mg

3.3 

2.1 

1.6 

.3 

.3

Run 12

G 

nmg

3.0 

2.5 

1.6 

.3 

.2

Run 16

H 

nmg

3.3 

1.7 

1.8 

.3 

.2

j

mg

3.5 

2.3 

1.4 

.3 

.2

K 

nmg

4.2 

2.2 

1.9 

.3 

.2

Run 8.—Sample put in furnace at 480° C, heated to 500° C. Total heating time, 50 minutes.

Run 11.—Sample put in furnace at 460° C, heated to 510° C. (All magnetic at 500° C.) Total heating time, 25 minutes.

Run 12.—Sample put in furnace at 500° C; furnace kept at 500° C. Total heating time, 15 minutes.

Run 16.—Sample put in furnace at 480° C, heated to 500° C. Total heating time, 15 minutes.
H6 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

Stephenson, R. C., 1945, Titaniferous magnetite deposits of 

the Lake Sanford area, New York: New York State 

Museum Bulletin 340, 95 p.

Syono, Yashuko, 1965, Magnetocrystalline anisotropy and 

magnetostriction of Fe3O4-Fet.TiO4 series—with special 

application to rock magnetism: Japanese Journal of 

Geophysics, v. 4, no. 1, p. 71-143.
A Technique for the

Decomposition and Dissolution of Rocks

and the Determination of

Lithium, Calcium, and Magnesium

Using Atomic-Absorption Spectroscopy

By ALLEN L. MEIER

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1129-1

This technique eliminates fluoride precipitation 

encountered during hydrofluoric acid 

decomposition of rocks

CONTENTS

Page

Abstract _________________________________________ — — ________ — — __ — __ II

Introduction ____________________________________________ 1

Procedure ___________________________________________ 2

Apparatus and equipment _______________________________ — ___________ 2

Reagents ________________________________________ 2

Standards _-______________________________________ 2

Sample decomposition and dissolution _______________________________ 2

Estimation ___________________________________________ — ____ — ___ 2

Results and discussion _____________________________________________ — ___ 3

References cited ________________________________________________________ 5

TABLES

Page

TABLE 1. Operating conditions used with the atomic-absorption instrument __________________________ — __________ 13

2. Readings obtained for lithium, calcium, and magnesium on the atomic-absorption instrument ___ — ______ 3

3. Comparison of replicate analyses using three techniques for decomposition and dissolution of rocks _______ 4

4. Comparison of lithium, calcium, and magnesium as determined by proposed technique with recommended

values for some standard rocks ______________________________________________________________ 4

in

SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

A TECHNIQUE FOR THE DECOMPOSITION AND DISSOLUTION OF ROCKS

AND THE DETERMINATION OF LITHIUM, CALCIUM, AND MAGNESIUM

USING ATOMIC-ABSORPTION SPECTROSCOPY

By ALLEN L. MEIER

ABSTRACT

Hydrofluoric acid is used in the proposed technique for the 

decomposition of rocks; a combination of hydrochloric acid 

and boric acid is used for sample dissolution prior to the 

determination of lithium, calcium, and magnesium using 

atomic-absorption spectroscopy. Results obtained using the 

proposed technique compare favorably with results obtained 

using other techniques. The problem of fluoride precipitation 

encountered in techniques using hydrofluoric acid for sample 

decomposition is eliminated with the use of boric acid.

INTRODUCTION

The decomposition of silicate rocks is usually accomplished by fusion with carbonate or borate fluxes 

or by using hydrofluoric acid with a mixture of other 

acids. The flux or hydrofluoric acid attacks the silicate, rendering the rock soluble in acid or water. The 

solution produced is used for subsequent analysis.

Fusion with carbonate or borate fluxes has been 

used for the decomposition of silicate rocks by Ingamells (1964), Suhr and Ingamells (1966), Shapiro 

(1967), Van Loon and Parissis (1969), Medlin and 

others (1969), Abbey (1970), O'Gorman and Suhr 

(1971), Abbey and others (1974), and Saavedra 

and others (1974). Cremer and Schlocker (1976) 

reported that the use of lithium borate-mineral acid 

in the decomposition and dissolution of silicate rocks 

was unsatisfactory in attacking some accessory minerals. Other problems with fusion techniques are 

that a high salt concentration is added to the solution to be analyzed and that the determination of the 

ion used in the flux is precluded (Bernas, 1968).

Langmyhr and Sveen (1965) investigated the decomposition of silicate rocks in hydrofluoric acid and 

found that 21 of 28 major and some minor minerals 

that may be present in silicate rocks were decomposed effectively at 95° C. The remainder of the minerals, with the exception of topaz, decomposed at 

higher temperatures in a TeflonMined bomb. Langmyhr and Sveen (1965) also reported that hydrofluoTic acid alone was more effective than a mixture 

of acids.

Decomposition of rocks with hydrofluoric acid 

leads to the precipitation of slightly soluble fluorides 

(Langmyhr and Sveen, 1965; Dolezal and others, 

1968; Bernas, 1968; Meier, 1976). Langmyhr and 

Sveen (1965) used an aluminum salt to complex and 

dissolve precipitated fluorides. Bernas (1968) reported the use of boric acid to dissolve precipitated 

fluorides. Fluoride removal can also be accomplished 

by evaporation to dryness with perchloric acid or 

sulfuric acid (Langmyhr and Sveen, 1965; Langmyhr and Paus, 1968; Ward and others, 1969). Sulfuric acid should not be used if atomic-absorption 

determinations are to be made because sulfate may 

cause interference (Langmyhr and Paus, 1968).

The proposed decomposition and dissolution procedure provides a rapid and efficient technique to 

dissolve rocks for atomic-absorption analysis. This 

technique has the advantages of hydrofluoric-acid 

decomposition without the use of perchloric acid for 

fluoride removal, particularly when a laboratory is 

not equipped with the fume hoods that are necessary 

for the safe use of perchloric acid. The decomposition and dissolution procedure used to provide a solution for the determination of lithium, calcium, and 

magnesium can also be used for the determination of 

other major and minor metal constituents of silicate 

rocks. Silicon cannot be determined, however, be1 Any use of trade names and trademarks in this publication is for 

descriptive purposes only and does not constitute endorsement by the 

U.S. Geological Survey.

II
12 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

cause it is removed as a volatile tetrafluoride during 

the decomposition of the rock.

PROCEDURE

APPARATUS AND EQUIPMENT

Teflon beakers: 50 mL [molded of TFE Teflon].

Volumetric flasks: 100 mL and 10 mL.

Hot plate.

Wash bottle.

Atomic absorption spectrophotometer.

Hollow cathode lamps, Ca, Mg, Li.

REAGENTS

Boric acid solution: Dissolve 50 g of reagent-grade 

boric acid in 1 liter of demineralized water.

Hydrochloric acid (6 normal) : Dilute 500 mL concentrated hydrochloric acid to 1 liter with demineralized water.

Hydrofluoric acid: 48 percent.

Lanthanum chloride solution (10 percent La) : 

Weigh 58.7 g lanthanum oxide (La2 03 ) into a 

1,000-mL beaker and wet with demineralized 

water. Cautiously add 100 mL of concentrated hydrochloric acid in small portions. When the oxide 

is completely dissolved, slowly dilute to 500 mL 

with demineralized water while stirring to avoid 

overheating.

Lanthanum chloride solution (1.1 percent La) : 

Dilute 110 mL of lanthanum chloride solution (10 

percent La) to 1,000 mL with demineralized 

water.

STANDARDS

Calcium stock solution, 1,000 fug mL" 1 : Dissolve 

2.497 g of dried calcium carbonate (overnight at 

100° C) in a mixture of 50 mL of demineralized 

water and 10 mL of 6 N hydrochloric acid. Dilute 

to 1,000 mL with demineralized water.

Lithium stock solution, 1,000 /xg mL- 1 : Dissolve 

9.9349 g of lithium nitrate in demineralized water 

and dilute to 1,000 mL with demineralized water.

Magnesium stock solution, 1,000 ^g mL- 1 : Dissolve 

1.000 g pure metallic magnesium in a minimum 

amount of 6 N hydrochloric acid (approx. 15 mL) 

and dilute to 1,000 mL with demineralized water.

Calcium working-standard solution: Prepare a series 

of standard solutions containing 0 to 100 /*g mL- 1 

by dilution of the calcium stock solution. For each 

mL of working standard to be prepared, add 0.1 

mL of lanthanum-chloride solution (10 percent 

La), 0.05 mL of 6 N hydrochloric acid, and 0.05 

mL of boric-acid solution.

Lithium working-standard solution: Prepare a series 

of standard solutions containing 0 to 10 /*g mL- 1 

by dilution of the lithium stock solution. For each 

milliliter of working standard to be prepared, add 

0.05 mL of 6 N hydrochloric acid, and 0.05 mL 

of boric-acid solution.

Magnesium working standard solution: Prepare a 

series of standard solutions containing 0 to 10 /xg 

mL" 1 by dilution of the magnesium stock solution. 

For each milliliter of working standard to be prepared, add 0.1 mL of lanthanum-chloride solution 

(10 percent La), 0.05 mL of 6 N hydrochloric acid, 

and 0.05 mL of boric-acid solution.

SAMPLE DECOMPOSITION AND DISSOLUTION

1. Weigh 0.20 g of powdered rock or soil in a 50-mL 

Teflon beaker.

2. Add 15 mL of hydrofluoric acid to the beaker.

3. Place the beaker on a hot plate set on high (approx. 250° C), and heat until all of the acid has 

been boiled off and all fumes have dissipated.

4. Add 5 mL of 6 N hydrochloric acid, and heat 

until acid begins to boil.

5. Add 5 mL of boric acid solution, and heat until 

the solution comes to a slight boil.

6. Remove the beaker from the hot plate, and transfer the solution to a 100-mL volumetric flask. 

Dilute to volume with demineralized water. 

Mix well by shaking, and use for lithium 

determination.

7. Transfer a 1-mL aliquot of the solution used for 

lithium determination to a 10-mL volumetric 

flask, and dilute to volume with lanthanumchloride solution (1.1 percent La). Mix well by 

shaking, and use for calcium and magnesium 

determination.

ESTIMATION

An atomic-absorption spectrophotometer is set to 

the operating conditions recommended by the manufacturer and calibrated using prepared working 

standards for each element. Lithium is determined 

by aspirating the solution contained in the 100-mL 

volumetric flask; calcium and magnesium are determined by aspirating the solution in the 10-ml volumetric flask. Concentration in the samples is calculated as follows:

ppm Li = instrument reading in /xg 

mL- 1 x 500, and

percent Ca or Mg = instrument reading in /xg 

mL- 1 X 0.5
DETERMINATION OF LITHIUM, CALCIUM, MAGNESIUM BY ATOMIC-ABSORPTION SPECTROSCOPY 13

Sensitivity and detection limits vary from one 

atomic absorption instrument to another; therefore, 

absolute limits of detection and working ranges are 

not stated. The working range for each element is 

limited to the linear portion of a curve plotted from 

concentration versus absorbance. This range can be 

extended by using an instrument with scale-expansion and curve-correction capabilities, reducing sensitivity by rotating the burner, or by diluting the 

sample. Any or all of these techniques should be used 

to fit the concentration range of the samples to be

TABLE 1.—Operating conditions iised with the atomic-absorption instrument

Lithium Calcium Magnesium

Grating ____——_ — _. 

Wavelength counter __. 

Slit _______________

Scale expansion _______

Lamp current _________

Source lamp __________

Integration ___________

Burner _______________

Fuel ___________. 

Oxidation ____________

Flame type ___________

Filter ___________

.VIS ____VIS ______UV

-335 ____211 ____285. 

.3 ______4 ______4. 

.1 x -——-1 X — — 1 X 

.10 ma ___10 ma __10 ma.

-Li _____Ca ____Mg. 

.3 sec ___3 sec ___3 sec. 

.10 cm ___10 cm _____10 cm.

-Acetylene -Acetylene -Acetylene. 

_Air ____Air _____Air.

-Lean, blue -Lean, blue-Lean, blue.

-In _____Out ____Out.

TABLE 2.—Readings obtained for lithium, calcium, and magnesium on the atomic-absorption instrument

(fig mL'1 )

0.1 _ _ . 1 _ __ .

2 _ __ . 3 _____

- 5 _ _ ___.

10 _ .

0.7 _ ___ .

1 _

2

3 _ _ _ . 10

25 _ _

50 ________

100 _ _ .

0.1 __ _ _.

I

2 __ ___

3 _ _ _

5 __ _ . 10 __ ___.

25 __ __

50 _ _

Absorbance

Burner in line

Lithium

0.017

._ _ __ .172

. _ __ .337

. _ _ _ .488

- __ __ .766

- __ _ 1.313

Calcium

- ____ 0.009

._ __ _ .101

- _ _ .191

.424

_______ .835

_ _ _ 1.502

__ _ __ 1.843

1.905

Magnesium

0.082

___ _ .753

_ _ _ 1.242

_ __ __ 1.724

. _ 1.939 ( 2 )

_______ (»)

_______ (•)

Burner rotated 90°

0)

0.007

.013

.020

.034

.068

(')

0.003

.006

.015

.031

.071

.146

.292

0.003

.029

.059

.089

149

.291

1.741

1.405

1 Below absorbance range of the instrument.

2 Above absorbance range of the instrument.

analyzed to the capabilities of the instrument to be 

used. The operating conditions listed in table 1 were 

used with a Perkin-Elmer model 603 atomic-absoTptiom instrument, and the readings obtained using 

those conditions are given in table 2.

Typical working ranges, using the described procedure without use of curve correction, are as 

follows:

Lithicum concentration in sample

0- 500 ppm ______Burner in line with sample beam. 

500-5000 ppm ______Burner rotated 90° to sample beam. 

>5000 ppm _____..Dilution.

Calcium concentration in sample

0- 2 percent __________ Burner in line with sample beam.

2-50 percent ______Burner rotated 90° to sample beam.

>50 percent __________Dilution.

Magnesium concentration in sample

0 -0.5 percent ______-Burner in line with sample beam.

0.5-5 percent ____Burner rotated 90° to sample beam. 

>5 percent _____ — -Dilution.

RESULTS AND DISCUSSION

Using the technique discussed in this paper, five 

replicate analyses were made on each of five selected 

samples to establish a mean value and a confidence 

interval for lithium, calcium, and magnesium. The 

same samples were also analyzed by two other methods. One of the methods, described by Ward and 

others (1969), uses a combination of nitric, perchloric, and hydrofluoric acids for sample decomposition, followed by hydrochloric-acid dissolution of the 

residue. The other method employs the decomposition procedure of Ward and others (1969) but was 

followed by the proposed hydrochloric- and boricacid dissolution. Table 3 compares results obtained 

by these three methods.

Five replicate analyses were made on each of six 

standard rock samples to establish a mean value and 

to determine the standard deviation for lithium, calcium, and magnesium by the proposed method. Comparisons of the results to recommended values are 

shown in table 4.

The low values obtained for calcium on sample 

MAG 638 and for magnesium on sample MAG 754 

using a combination of nitric, perchloric, and hydrofluoric acids (Ward and others, 1969) indicate that 

perchloric acid is not completely effective in the removal of fluorides when high concentrations of calcium or magnesium are present. The addition of 

boric acid in the dissolution procedure effectively 

redissolves these precipitated fluorides. The relatively good agreement of values obtained by the 

technique proposed in this paper with the other tech-
14 SHORTER CONTRIBUTIONS TO GEOCHEMISTRY, 1979

TABLE 3. — Comparison of replicate analyses using three techniques for decomposition and dissolution of rocks

[Values shown are averages of replicate analyses and limits at the 95 percent 

confidence level. Lithium analyses in ppm, calcium and magnesium analyses 

in percent]

Technique 1

1

2

3

1

2

3

1

2

3

Element

Li

Li

Li

Ca

Ca

Ca

Mg

Mg

Mg

Sample number and material

MA I 180

840

802

790

3

3

2

3

3

3

Clay

+14

+11

+16

.10+ .05

.01+ .09

.98+ .18

.25+ .05

.10+ .04

.07+ .16

MA I 413

Clay

135

148

140

3.

4.

3.

3.

3.

3.

+3

+7

+3

90+ .27

10+ .18

88+ .19

27+ .16

40+ .16

24+ .14

MAH 430

Tuff

705

709

714

7

7

7

1

1

1

+23

+21

+12

.43+ .64

.42+ .27

.36+ .10

.48+ .13

.45+ .07

.47+ .01

MAG 754

Carbonate

574 + 6

584 +14

542 +25

2*. 1 4+ .

2.20+ .

2.18+ .

25.1 + .

25.2 + .

19.6 + .

09

11

07

1

1

1

MAG 638

Carbonate

787 +30

758 +17

775 +28

25.0 + 1

25.7 +

23.8 +

3.88+

3.98+

3.94+

.3

.3

.9

.32

.11

.18

techniques:

1. HF decomposition, HC1-H 3 B0 3 dissolution (proposed in this paper).

2. HF-HN0 3 -HC104 decomposition, HC1-H 3 B0 3 dissolution.

3. HF-HN0 3 -HC104 decomposition, HC1 dissolution.

TABLE 4.—Comparison of lithium, calcium, and magnesium as determined by the proposed technique, with recommended values

for some standard rocks

[Leaders (—) indicate no value available]

Sample No. 

and material

NBS 97a,

NBS120a, 

phosphate rock--

G-2,

D7S-1,

PCC-1,

GSP-1, 

granodiorite----

Average, 

proposed 

technique 

(ppm)

517 

6.4 

29.0 

<1 

<] 

28.4

Lithium

Standard Recommended 

deviation value 

(ppm)

2.39 !511 

.89 

1.00 2 34.8 

2< 2 

2 <2 

.55 2 32.1

Average, 

percent, 

proposed 

technique

0.072 

29.9 

1.29 

.095 

.32 

1.34

Calcium

Standard 

deviation

0.002 

.50 

.080 

.009 

.047 

.026

Recommended 

value, in 

percent

!0.079 

'30.3 

2 1.39 

2.107 

2.36 

2 1.44

Average, 

percent, 

proposed 

technique

0.090 

.13 

.44 

30.1 

26.1 

.59

Magnesium

Standard 

deviation

0.002 

.002 

.008 

.45 

.45 

.025

Recommended 

value, in 

percent

io.ogo

1.19 . 

2.46 

2 30.0 

226.0 

2.58

Certified value, U.S. National Bureau of Standards. 

2 Value recommended by Flanagan (1973).
DETERMINATION OF LITHIUM, CALCIUM, MAGNESIUM BY ATOMIC-ABSORPTION SPECTROSCOPY 15

niques discussed shows it to be a useful procedure 

for decomposition and dissolution of rocks for 

atomic-absorption analysis, especially when perchloric acid cannot be used.

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atomic absorption spectroscopy, pt. 3 of A lithium-fluoborate scheme for seven major elements: Geological Survey 

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of rocks and minerals using an atomic absorption speHrophotometer, pt. 5 of An improved lithium-fluoborate 

scheme for fourteen elements: Geological Survey of 

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337..

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135-139.

Shapiro, Leonard, 1967, Rapid analysis of rocks and minerals 

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analysis based on the lithium metaborate fusion followed 

by atomic-absorption spectrophotometry: The Analyst, v. 

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& U.S. GOVERNMENT PRINTING OFFICE: 1980 O- 311-344/41