Alaska Geochemical Database: Mineral Exploration Tool for 

the 21st Century—PDF of Presentation

By Matthew Granitto, Jeanine M. Schmidt, Keith A. Labay, Nora B. Shew, and Bruce M. Gamble 

Open-File Report 2012–1060

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

KEN SALAZAR, Secretary 

U.S. Geological Survey 

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia: 2012 

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod 

Telephone: 1-888-ASK-USGS 

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its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov 

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Suggested citation: 

Granitto, Matthew, Schmidt, J.M., Labay, K.A., Shew, N.B., and Gamble, B.M., 2012, Alaska Geochemical 

Database—Mineral Exploration Tool for the 21st Century—PDF of presentation: U.S. Geological Survey 

Open-File Report 2012–1060, 33 p.

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endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 
iii

Contents

Abstract ......................................................................................................................................................................... 1 

Introduction .................................................................................................................................................................... 2 

Slides ............................................................................................................................................................................. 3 

References ...................................................................................................................................................................33
Alaska Geochemical Database—Mineral Exploration Tool 

for the 21st Century—PDF of Presentation

By Matthew Granitto, Jeanine M. Schmidt, Keith A. Labay, Nora B. Shew, and Bruce M. Gamble 

Abstract

The U.S. Geological Survey has created a geochemical database of geologic material samples 

collected in Alaska. This database is readily accessible to anyone with access to the Internet. Designed 

as a tool for mineral or environmental assessment, land management, or mineral exploration, the initial 

version of the Alaska Geochemical Database—U.S. Geological Survey Data Series 637—contains 

geochemical, geologic, and geospatial data for 264,158 samples collected from 1962–2009: 108,909

rock samples; 92,701 sediment samples; 48,209 heavy-mineral-concentrate samples; 6,869 soil samples; 

and 7,470 mineral samples. In addition, the Alaska Geochemical Database contains mineralogic data 

for 18,138 nonmagnetic-fraction heavy mineral concentrates, making it the first U.S. Geological Survey 

database of this scope that contains both geochemical and mineralogic data. Examples from the Alaska 

Range will illustrate potential uses of the Alaska Geochemical Database in mineral exploration. 

Data from the Alaska Geochemical Database have been extensively checked for accuracy of 

sample media description, sample site location, and analytical method using U.S. Geological Survey 

sample-submittal archives and U.S. Geological Survey publications (plus field notebooks and sample 

site compilation base maps from the Alaska Technical Data Unit in Anchorage, Alaska). The database 

is also the repository for nearly all previously released U.S. Geological Survey Alaska geochemical 

datasets. Although the Alaska Geochemical Database is a fully relational database in Microsoft®

Access 2003 and 2010 formats, these same data are also provided as a series of spreadsheet files in 

Microsoft®Excel 2003 and 2010 formats, and as ASCII text files. A DVD version of the Alaska 

Geochemical Database was released in October 2011, as U.S. Geological Survey Data Series 637, and 

data downloads are available at http://pubs.usgs.gov/ds/637/. Also, all Alaska Geochemical Database 

data have been incorporated into the interactive U.S. Geological Survey Mineral Resource Data web 

portal, available at http://mrdata.usgs.gov/.

Introduction

The U.S. Geological Survey (USGS) has recently completed a comprehensive geochemical 

database for Alaska: the Alaska Geochemical Database (AGDB). The AGDB has been published 

digitally as a USGS Data Series DVD (Granitto and others, 2011) and information about the AGDB 

dataset is summarized in a recent USGS Fact Sheet (Schmidt and Granitto, 2011). This report is a 

record of a presentation prepared by the authors and presented to the Alaska Miners Association Annual 

Convention in Anchorage, Alaska, on November 9, 2011 by senior author Matthew Granitto. It 

describes information about the AGDB database and gives examples from two areas of the Alaska 

Range to illustrate how AGDB data can be sorted, selected, and combined with other geological 

information (for example, the Alaska Resource Data Files (ARDF)) to provide information and analysis 

useful for mineral exploration or mineral-assessment purposes.

1
2
USGS geochemical data for geologic material samples collected in Alaska are now readily accessible to 

anyone with a powerful personal computer and access to the Internet. The Alaska Geochemical 

Database (AGDB)—Geochemical Data for Rock, Sediment, Soil, Mineral and Concentrate Sample 

Media was released in October, 2011 as the USGS publication Data Series 637 

(http://pubs.usgs.gov/ds/637).

3
The AGDB DVD contains geochemical, geological, and mineralogical data for geologic material 

samples collected in Alaska and from its adjacent marine waters; all have geographic coordinates. For 

ease of use, the data have been grouped by sample-media type. For example, rock data are kept 

separate from data for other sample-media types. 

4
A Microsoft® Access relational database, constructed in both 2010 and 2003 versions, is the primary 

repository of this data. This DVD also provides the data as Access® “flat file” or spreadsheet tables, 

which is useful for those who are not familiar with relational databases. 

The data are also provided as Microsoft® Excel 2010 spreadsheets, and as ASCII text files. 

The AGDB DVD is available from the authors (granitto@usgs.gov or jschmidt@usgs.gov). The data, 

pamphlet, and metadata files can also be downloaded from the USGS Publications Warehouse website 

(http://pubs.usgs.gov/ds/637).

5
The data types, sample media, Quality Assurance/Quality Control procedures, metadata, and references 

of the AGDB are summarized in a 2-page Fact Sheet which is available in hard copy from the authors 

(granitto@usgs.gov or jschmidt@usgs.gov) or online at the USGS Publications Warehouse 

(http://pubs.usgs.gov/fs/2011/3130). 

6
The data in the AGDB consist of both recent and legacy geochemical data. The USGS legacy databases 

RASS (Rock Archival Storage System) and PLUTO contributed more than 75 percent of all the AGDB 

data. Most of the remainder is from the current USGS National Geochemical Database (NGDB). The 

NGDB is the data warehouse for all USGS geochemical data from all 50 states and from foreign 

countries. 

Most of the AGDB data has been released over the past 45 years as datasets of varying size in paper or 

digital publications. For the first time, these and other data have been compiled to produce an 

exhaustive geochemical database for geologic media samples collected in Alaska in support of USGS 

programs. 

The AGDB contains Alaskan datasets more recently released to the public, including datasets from 

projects such as the Tintina Gold Province, Federal Lands in Alaska—Geologic Studies (reanalysis of 

Alaska Range stream sediments), the Taylor Mountains quadrangle, the Pebble Cu-Mo-Au deposit, and 

the Red Dog and Drenchwater Creek Zn-Pb-Ag deposits. All of the Alaskan sample data from the 

National Geochemical Survey (which includes the reanalysis of National Uranium Resource Evaluation 

program archival samples) are also included in the AGDB. 

7
Work on the AGDB was initiated by the Minerals Data Information Rescue in Alaska Program from 

1998 to 2003 in an effort to make USGS Alaskan geochemical data readily available to the public. Data 

from samples analyzed between 1962 and 1995 were first released as spreadsheets accessible at USGS 

websites. 

The AGDB was completed under the Federal Lands in Alaska—Geologic Studies project as a fully 

relational geochemical database. Data from samples collected and analyzed from 1996 to 2009 have 

been included, which brings Alaskan geochemical data up to date for the user. 

8
The majority of the analytical data in the AGDB is from rock and stream-sediment samples, most of 

which were collected by the Alaska Mineral Resource Assessment Program (AMRAP) during the 

1970s and 1980s. Most AGDB materials were collected by USGS field parties between 1962 and 2009, 

although the database includes samples collected by the Alaska Division of Geologic and Geophysical 

Surveys, the U.S. Bureau of Mines, and by the National Uranium Resource Evaluation (NURE) 

program. The data from 6,686 reanalyzed NURE sediment and soil samples (that is, the National 

Geochemical Survey) are included in the AGDB. 

In the AGDB, heavy-mineral concentrates, primarily derived from the panning of bulk stream sediment 

in the field, have been given their own media type which keeps their data easily separate from that of 

other sample media. Detailed sample-preparation information is included in the concentrate dataset. 

Data for mineral and soil samples are also included in the AGDB. Although most of the mineral data 

are derived from samples for geochronology, the geologic ages and dating analyses are not included in 

the AGDB. 

The AGDB is an enormous database—it contains data for more than 264,000 geologic material 

samples. 

9
The AGDB also contains all known USGS Alaskan panned-concentrate mineralogy data. This 

represents more than 18,000 samples—most of which also have chemical data for the same nonmagnetic sample fraction. Most of these samples were collected for AMRAP projects, but 

mineralogical data from the recent Taylor Mountains quadrangle project are included here as well. 

Mineralogical identifications were derived from optical-microscopy observations of sample grains—

most of which was done by Richard B. Tripp of the USGS, a fact that provides continuity of analysis 

and consistency of data reporting. 

10
Over the years, USGS scientists recognized several problems with legacy databases. Three primary 

issues were: location coordinates (either incorrect or lacking), sample media (not precisely identified), 

and analytical method of detection (also not precisely identified, or actually missing from the early 

PLUTO database structure). 

In 1998, re-processing of Alaskan data from these databases was initiated to correct errors in sample 

locations, to add sample locations when missing, and to correctly identify the sample media and 

analytical protocol of each record. This re-processing consisted of checking the information on sample 

media, location, and analytical method against the original sample submittal forms, the original 

laboratory reports, published reports, field notebooks and sample location base maps, and discussions 

with sample submitters and analysts. As necessary, fields were added to the original data to more fully 

describe the sample-preparation methods used and sample media analyzed. Sample records that could 

have been entered in RASS and PLUTO, but were not, have been included, resulting in the addition of 

tens of thousands of sample data records to the AGDB. 

For sample media, details regarding media type, mineralization, alteration, stratigraphy, geologic age, 

sample source, collection method, and sample preparation have been checked, corrected when in error, 

and added when absent but later found. 

For sample location, many archive sample-site maps were digitized and sites plotted to gain new or 

more accurate coordinates. The use of geographic information systems has been a great assistance in 

this effort. Detailed information regarding sample locations was also added to the AGDB. 

11
1:250,000-scale quadrangles are often used to group Alaskan sample data, so the names of these 

quadrangles were added as attributes to the AGDB. 

12
These are the sample localities of the current version of the AGDB. The blue dots are sediment, soil, 

and heavy-mineral concentrate sample localities. The red dots are rock and mineral sample localities. 

The red dots often overlie, and in some cases obscure, the blue dots. Not shown on this map are a few 

sample localities in the western Aleutian Islands. Most of the quadrangles with heavy sample density 

represent USGS AMRAP study areas. 

13
Details of the analytical methods, such as sample digestion and decomposition, were added as the 

method types were researched, documented, and referenced in the AGDB. The actual analytical data 

were not checked in great detail, but obvious errors were corrected. All corrections, additions, and 

enhancements will be entered into the NGDB. In January, 2012, an enhanced interface to search, select, 

and retrieve AGDB data by various criteria (for example, hydrologic unit) was made available at the 

USGS Mineral Resource Data website. The refined data in the AGDB will also be input in the national 

databases already at this site. 

14
The AGDB is a Microsoft® Access relational database. Because of the scope and complexity of 

geologic-materials data collected by diverse Alaskan geochemical-assessment projects, a relational 

database structure was designed for data storage. It is both a tool to be used for data synthesis and 

analysis, and an archive of data collected during these projects. The database structure and format are a 

modification of that used by the NGDB because more than 85 percent of the data were retrieved from 

the NGDB. These data are also provided as Access “flat file” or spreadsheet tables, as a series of 

spreadsheet files in Microsoft® Excel, and as ASCII text files. 

15
Microsoft® Access has programmatic size limitations that needed to be addressed during the creation of 

the AGDB. The AGDB actually consists of two databases. All of the data are contained in the split 

relational database that is AGDB and AGDB_Chem. As these databases are linked by the common 

field LAB_ID, they can reside on a computer hard drive as if they were one entity. Together, they 

greatly exceed 2 GB, which is the maximum allowable database size limit set by Access. When linked, 

they operate very well together. 

16
The beauty of relational databases is illustrated by the relationships of data tables to one another. The 

Geol table contains geospatial, geologic, and descriptive attributes for all sample records (recs) in the 

AGDB with chemical and mineralogical data. 

Related to the Geol table is the Mnrlgy table that contains all the mineralogical data found in the 

AGDB. All “mnrlgy” records are linked to “geol” records in a one-to-one relationship, where each 

“mnrlgy” record is also found in the Geol table. 

Also related to the Geol table is the Chem table that contains all the chemical determination data found 

in the AGDB. All “chem” records are linked to “geol” records in a one-to-many relationship, where one 

“geol” record may have one or more “chem” records associated with it. The relationship diagram shows 

the three core tables: Geol, Chem, and Mnrlrgy. Note the size of the Chem table—it records nearly 

9.7 million chemical determinations as unique individual records. 

17
The reference or “lookup” tables provide definitions and descriptions for all of the data fields in the 

AGDB and function as “on-board” metadata within the database. Information regarding the method of 

analysis or measurement used to obtain data is found in the AnalyticMethod table—a look-up table 

that provides additional information on the 85 field and laboratory techniques used for analysis of the 

various geologic materials. The table includes a description of the analytical methods and relevant 

published references and is linked to bibliographic reference information in the table 

AnalyticMethodBiblio—a table of references for analytical methods used to obtain chemical data. 

18
The table FieldNameDictionary is also a reference table. It contains the field name, size, definition, 

and general data type of the 974 fields that are used in the tables of the AGDB, as well identifying the 

table or tables in which these fields appear. FieldNameDictionary is a lookup table that is not directly 

linked (white line) to other tables in the relational database. It is of particular importance for the nondatabase user as it also contains the descriptions of field names used in the Excel and ASCII text data 

tables. 

This relational database structure provides for efficient storage of information and built-in dataverification checks. For example, all valid chemistry results must have corresponding geologic sample 

information. Relations between these tables are depicted as lines. Geol is linked to Chem by including 

a common field (LAB_ID) in both tables. Therefore, a chemical value cannot exist without having a 

corresponding sample in Geol. Data may be extracted from the AGDB to meet specific user needs by 

constructing user-defined queries. USGS Data Series 637 (http://pubs.usgs.gov/ds/637) contains a 

number of completed sample queries to help the user take advantage of the relational nature of the 

AGDB (Granitto and others, 2011). 

19
Let’s look at some of the types of data included in the AGDB and what you can do with it. We will start 

with the Clearwater Mountains area in the central Alaska Range, spanning the Healy and Mt. Hayes 

quadrangle boundary. 

20
Exploration for nickel, copper, and platinum-group-element sulfide deposits is currently underway in 

the Amphitheatre Mountains, which straddle the east boundary of this map, east of the Maclaren River. 

The geologic units of primary interest, the Triassic (Tr) Nikolai Greenstone and related gabbro and 

ultramafic (UM) sills (in purple), continue westward into the Clearwater Mountains, which take up the 

central and western part of this map, west of the Maclaren River. Other geologic units represented on 

this map are Permian-Pennsylvanian (PIP) metasediments (in blue), the Mesozoic Maclaren 

metamorphic flysch (in green), and Tertiary-Cretaceous (TK) granites. Note that the Healy/Mt. Hayes 

quadrangle boundary is indicated by a change in the style of mapping of Quaternary units (in tan), as 

this slide shows a compilation of two geologic maps (Wilson and others, 1998). 

21
This map of the same area shows that analytical geochemistry or mineralogy data are available for 

1,616 samples (spls) of geologic materials from this 1,350 square mile area. Heavy-mineral-concentrate 

sample localities are a subset of sediment localities, because the concentrates were derived from the 

panning of bulk sediments in the field. All mineralogy localities are also concentrate localities. In the 

next few slides, we will illustrate how the AGDB data can be used to identify areas of exploration 

interest. 

22
We plotted the distribution of copper in bulk stream sediments versus that in panned concentrates and 

can compare those distributions to the bedrock geology. Copper values in stream sediments (blue 

circles) are uniformly high in areas underlain by the Nikolai Greenstone (in purple) with a cluster of 

very high values in the Pass Creek area (lower left) of the southern Clearwater Mountains. 

Copper in concentrate samples (red squares), in contrast, is elevated in several areas underlain by 

Cretaceous metamorphic rocks and Tertiary granites (in the greens and reds in the upper central part of 

the map). 

One area indicated as of possible exploration interest is the central ridge of the Clearwater Mountains 

(inside the red oval in this map), where both sediment and concentrate samples are consistently 

elevated in copper, and where geophysical data suggest that the Maclaren metamorphic rocks may form 

a relatively thin sheet thrust southward over Nikolai and related magnetic rocks. 

23
If we look at the distribution of nickel, we find that the high nickel concentration in stream sediments 

(blue circles) are clustered in two areas (inside the blue ovals in this map): Pass Creek area on the 

southern ridge of the Clearwater Mountains (in the lower left corner of the map), and in the 

northwestern Amphitheatre Mountains (at the right edge of the map). Heavy-mineral concentrates (red 

squares) show a completely different distribution of high nickel values (inside the red oval in this map), 

located in the Maclaren metamorphic belt and Tertiary granitic rocks north of the region underlain by 

Nikolai Greenstone. 

24
Data from the AGDB can also be combined with other types of geologic information to further develop 

and refine exploration targets. The Alaska Resource Data File (ARDF) is the USGS database of mines, 

prospects, and mineral occurrences for Alaska. In this example, we have plotted from the ARDF 

occurrences in which either nickel (blue triangles) or copper (black triangles) were the primary or 

secondary commodities present. Known nickel-bearing occurrences cluster at the east end of the map 

area, unlike a much broader distribution of copper-bearing prospects, the majority of which are 

underlain by Nikolai Greenstone (in purple). 

However, the AGDB includes mineralogical observations as well as analytical data. A search of AGDB 

mineralogic data for heavy-mineral-concentrate samples in which chalcopyrite was optically identified 

shows a distribution (red circles) significantly different than that of the known copper occurrences. This 

suggests that copper-sulfide minerals (such as chalcopyrite) have been derived from sources much 

more widely distributed than the known prospects. 

25
Our second example of AGDB data use is in the area near Mt. Estelle in the western Alaska Range, 

situated at the junction of the Lime Hills, McGrath, Talkeetna, and Tyonek quadrangles. 

26
The 3,390-square-mile area around Mt. Estelle includes 4,157 samples (spls) for which analytical 

geochemistry or mineralogy data are available. This plot shows the variation in sample media types, 

sample density, and sample distribution within our area of interest. Note that the McGrath quadrangle 

(upper left) and the Tyonek quadrangle (lower right) show limited sample distribution and only a single 

sample media type—sediment samples (black circles). Distribution plots such as this identify target 

regions where additional sampling of one or more media is needed. 

27
Between 2007 and 2009, stream-sediment samples collected during the Heavy Metals Program (1966-

1970) and the Alaska Mineral Resource Assessment Program (AMRAP, 1970s-1980s) were retrieved 

from the USGS sample archives and reanalyzed for additional elements. In this case, sample points in 

red are those for which no gold determinations existed prior to this reanalysis program. These new data 

identified new areas with anomalous gold values. Both the old and new chemical data for these and 

similarly reanalyzed samples are included in the AGDB and are linked by field IDs so that reanalyzed 

samples can be clearly identified. 

The map background shown here (from Wilson and others, 1998) indicates Cretaceous flysch of the 

Kahiltna assemblage and the Kuskokwim Group in pale green, Tertiary plutonic and volcanic rocks in 

various shades of red and purple, and pre-Mesozoic sedimentary rocks in blue. 

28
The mineralogy data included in the AGDB provides yet another type of exploration information. Here 

in the Mt. Estelle area high values of gold analyzed from heavy-mineral-concentrate samples (red 

squares) and bulk stream sediments (blue circles) do not indicate all of the areas in which visible gold 

has been identified by optical microscopy (yellow squares). 

29
AGDB data can also be combined with geologic information from other sources, such as the Alaska 

Resource Data Files (ARDF). In this plot, concentrate samples from the AGDB in which cassiterite was 

identified optically (red triangles), indicate a wide range of potential tin occurrences. Many of these are 

in regions not previously identified as having mineral occurrences (from the ARDF) in which tin (blue 

circles) or fluorite (black circles) are the primary commodity. 

30
AGDB mineralogical data also provide information not necessarily available from the analytical data. 

Comparing the distribution of high molybdenum values in concentrates (red squares) and in stream 

sediments (blue circles) with the distribution of molybdenite identified optically (black triangles) 

highlights three distinct regions of potential for molybdenum-bearing mineral occurrences, each 

associated with a different suite of igneous rocks (shown in the reds and pinks). 

31
Version 1.0 of the AGDB is currently available as a DVD or for download online. It is also available on the 

USGS Mineral Resource Data website (http://mrdata.usgs.gov), where it may be queried interactively and 

offers a variety of downloadable formats. Version 2.0 of the AGDB, to be released in 2012, will include 

analytical data for water-, organic-, and leachate-sample media. 

For further information on the AGDB, copies of Fact Sheet 2011-3130 are available at the USGS 

Publications Warehouse (http://pubs.usgs.gov/fs/2011/3130). 

If you have comments regarding the AGDB format and coverage, or corrections to current data, please 

send them to Matt Granitto or Jeanine Schmidt. 

32
References Cited

Granitto, Matthew, Bailey, E.A., Schmidt, J.M., Shew, N.B., Gamble, B.M., and Labay, K.A., 2011, 

Alaska Geochemical Database (AGDB)—Geochemical data for rock, sediment, soil, mineral, and 

concentrate sample media: U.S. Geological Survey Data Series 637, 31 p. pamphlet and database, 1 

DVD. (Available at http://pubs.usgs.gov/ds/637.) 

Schmidt, J.M., and Granitto, Matthew, 2011, The Alaska Geochemical Database, v. 1.0—Geologic 

Materials: U.S. Geological Survey Fact Sheet 2011–3130, 2 p. (Available at 

http://pubs.usgs.gov/fs/2011/3130/.) 

Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, 

Geologic map of Central (Interior) Alaska: U.S. Geological Survey Open-File Report 98–133-A, 

v.1.2. (Available at http://pubs.usgs.gov/of/1998/of98-133-a/.) 

33