Franciscan deposits differ mineralogically from Olympic
Peninsula deposits in several ways. Carbonate-bearing as-
semblages seem to be more common in Franciscan deposits
but are minor in Olympic Peninsula deposits. In constrast,
Olympic Peninsula deposits seem to be more silicate rich, and
bementite and neotocite are abundant manganese silicates.
Furthermore, hausmannite is an important economic ore
mineral in Olympic Peninsula deposits, whereas psilomelane
is important in Franciscan deposits.

Accessory pyrite and quartz occur in all the deposit types.
Copper minerals, hematite, calcite, and barite are present in all
except Cyprus deposits. Cinnabar is presentin Franciscan and
Olympic Peninsula deposits but is absent in Cuban and
Cyprus deposits.

Host Rock

The host rocks among the four deposit types are distinct
(table 2). The major host rock in Cuban deposits is dacitic to
basaltic pyroclastic rocks and flows. Franciscan deposits are
hosted mostly in white, red, or green massive to thin-bedded
chert. Olympic Peninsula deposits are hosted in basalt or in
the contact between basalt and limestone. Cyprus deposits are
hosted in basalt flows and sedimentary rocks, such as clay,
marl, chalk, or chert.

Shape, Dimensions, and Volume

Generally, ore bodies in the deposits are thin, narrow to
wide ellipsoids; these shapes suggest a genetic association
with linear structural features on the sea floor where the
deposits were deposited. The range of shapes in the bedding
plane is shown schematically by region and deposit type in
figure 4. Lengths and widths among the deposit types differ
significantly except among Cuban and Cyprus deposits,
which are the largest in extent. Cyprus deposits are also
significantly thicker than the other deposit types. Length-to-
width ratios among the types are similar; for example,
Franciscan, Cuban, and Olympic Peninsula deposits are about
3 times as long as they are wide, and Cyprus deposits about 4
times as long as they are wide. Length-to-thickness ratios
range from 9 for Olympic Peninsula deposits to 47 for Cuban
deposits. Width-to-thickness ratios range from 3 for Olympic
Peninsula deposits to 18 for Cuban deposits. Interestingly, the
length-to-thickness and the width-to-thickness ratios are
similar for Franciscan and Cyprus deposits, two types formed
in similar tectonic environments. The volumes for Cyprus and
Cuban deposits are significantly larger than for Franciscan
and Olympic Peninsula deposits (fig. 7; table 3).

Tonnage

The differences in tonnage among the deposit types are
plotted in figure 18. Cyprus deposits have the largest median
tonnage, and Olympic Peninsula deposits the smallest. The

tonnages for Cyprus and Cuban deposits are significantly
larger than for Franciscan and Olympic Peninsula deposits.

Grade

The differences in manganese grade among the groups are
plotted in figure 19. Cuban deposits have the highest median
grade, and Cyprus deposits the lowest. Manganese grades
among the deposit types do not differ significantly, except for
Cyprus deposits. The median iron grade for Cyprus deposits
is at least 5 times that for the other types (fig. 20).

Contained Metal

The differences in contained manganese metal among the
deposit types are plotted in figure 21. The median contained
metal for Cuban deposits is significantly larger than for both
Franciscan and Olympic Peninsula deposits. Although,
Cyprus deposits do not differ significantly from the other
types, because of their wide range in Mn content they are the
largest in contained metal and tonnage of all submarine
volcanogenic deposits.

Mineral-Deposit Density

Mineral-deposit densities for the four deposit types are
listed in table 4. Deposit densities within each type vary by as
much as two orders of magnitude, as in Fiji (0.0066) and Cuba
(0.1), possibly because of the different levels of exploration in
these two countries or the favorability levels of different types
or ages of host rock. Deposit densities among the deposit
types differ; for example, in the Kitakami Mountains, north-
eastern Honshu, Japan (Franciscan type), and in the Troodos
Complex, Cyprus (Cyprus type), deposit densities differ by an
order of magnitude. Because the differences in mineral-
deposit densities within types can vary as much as those
among types, comparison of deposit densities among types
should be done with care.

APPLICATION OF THE MODELS AND
CONSTRAINTS ON GENETIC MODELS

The application or usage of the volcanogenic manganese
models for resource assessment is a three-step process
(Singer, 1975, 1984) that involves: (1) delineating a tract or
domain which contains rocks permissive for the occurrence of
a particular deposit type, (2) estimating the number of undis-
covered deposits, and (3) predicting the tonnage and grade
characteristics of the undiscovered deposits by analogy to
those of the same type known elsewhere. Combinations of
characteristics from the descriptive models (appendixes A-
D), particularly depositional environment, tectonic setting,
and rock types, allow boundaries to be drawn around tracts or
domains with geologic, geochemical, and geophysical con-
straints similar to the model. Each tract, defined in this way,

16 Models of Volcanogenic Manganese Deposits in Oceanic Environments


California, jasper and chert are the host rocks for 86 percent
of deposits. Jasper is a minor host rock in Cuba and Fiji.
Limestone, argillite, agglomerate, chert, marl, and volcanic
flows are all minor host rocks (table 2).

Shape and size.—Ore bodies of Cuban deposits are gen-
erally thin ellipsoids (fig. 4). Lengths range from 1.5 to 2,900
m, widths from 0.4 to 470 m, and thicknesses from 0.1 to 15
m. For 60 deposits, the median length is 99 m, the median
width 38 m, and the median thickness 2.1 m (table3). Because
of the small number of Cuban deposits in Turkey, Fiji, and
California, the sizes shown in figure 4 may not be representa-
tive of deposits in those regions.

Tonnage, grade, and volume.—For 84 Cuban deposits,
the median tonnage is 6,400 t, and the median manganese
grade is 39 weight percent Mn (figs. 9, 10). The mean iron
grade for 6 deposits is 4.4 weight percent Fe. The median
volume for 75 deposits is 6,040 m3 (fig. 7; table 3). Tonnage
is correlated with Mn content (r = 0.18, n = 84) and Fe content
(r = 0.8, n = 6) at the 5-percent-confidence level.

Mineral-deposit density—Deposit densities were
determined for Cuban deposits in the Oriente Province, Cuba,
using a 1:50,000-scale geologic map (Lewis and Straczek,
1955), and in Viti Levu, Fiji, using a 1:250,000-scale geo-
logic map (Rodda and Bank, 1966). In the east half of the
Cobre Formation, which consists of 1,197 km? of Upper

‘Cretaceous to middle Eocene limestone, tuff, and jasper, there

is 10x10" deposit per square kilometer (table 4). In the
pyroclastic member of the Cobre Formation, a similar deposit
density is expected. Deposit densities for the Cobre
Formation vary by as muchas three orders of magnitude (table
4). In Viti Levu, Fiji, manganese-bearing rock units, which
consist of 2,723 km? of Eocene to Pliocene andesite tuff and
sedimentary rocks, yield 6.6x10° deposit per square
kilometer (table 4). Deposit densities for individual rock units
in Viti Levu are listed in table 4.

Olympic Peninsula Type

The type area for the Olympic Peninsula type of Mn
deposits is the Olympic Peninsula, Wash. The deposits are
hosted in argillaceous red limestone lenses that occur within
asequence of tholeiitic pillow basalt or at the contact between
these two rock types. Some deposits occur within the basalt
in the absence of limestone. Tuff, agglomerate, argillite, and
graywacke are associated with the host rocks. These rocks,
which are Eocene, are believed to have formed as seamounts
in deep to shallow ocean basins; some of the basalt may have
been deposited subaerially (Cady, 1975). Appendix C con-
tains a descriptive model for Olympic Peninsula deposits in
the form of Cox and Singer (1986). A generalized model
based on the data of Park (1941, 1946) is shown in figure 11.

The ore bodies are commonly elongate tabular lenses,
concordant to bedding. The ore is finely crystalline, massive
or banded, with spongy or colloform structures, algal struc-
tures, or fecal pellets (that is, evidence of concretionary
growth). Silicates, carbonates, and oxides of manganese are
present; secondary manganese oxides form near the surface
and along joints as oxidation products of bementite and other
primary manganese minerals. Some veinlets of manganese
silicates, quartz, hematite, calcite, and barite are present
(Green, 1945; Magill, 1960; Cady, 1975).

Mineralogy.—The most abundant minerals in Olympic
Peninsula deposits are bementite, hausmannite, and neotocite
(table 1); less abundant minerals include pyrolusite, inesite,
braunite, rhodochrosite, rhodonite, and manganocalcite. The
silicate-oxide assemblage occurs in 77 percent of the cases,
followed by the carbonate-silicate-oxide assemblage (17
percent). Small blebs or seams of cinnabar and disseminated
specks of native copper and pyrite are locally present. Quartz,
hematite, calcite, and rare barite are gangue minerals.

BAR

an

an

AS S

awe . ~
DN, Voleanic rocks \)s>
DAD ARRAY
PPE PELE LLL LLL ILS
SS SS SS SS SS SSSA LESS
PAREAARE EAE EEA EES

Figure 8. Generalized model of a Cuban-type deposit, based on the data of Simons and

Straczek (1958).

10 Models of Volcanogenic Manganese Deposits in Oceanic Environments


Cady, W.M., 1975, Tectonic setting of the Tertiary volcanic
rocks of the Olympic Peninsula, Washington: U.S. Geo-
logical Survey Journal of Research, v. 3, no. 5, p. 573-582.

Constantinou, G., and Govett, G.J.S., 1972, Genesis of sulphide
deposits, ochre and umber of Cyprus: London Institution
of Mining and Metallurgy Transactions, v. 81, sec. B, no.
783, p. B34-B46.

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models:
U.S. Geological Survey Bulletin 1693, 379 p.

Crerar, D.A., Namson, Jay, Su Chyi, Michael, Williams, Loretta,
and Feigenson, M.D., 1982, Manganiferous cherts of the
Franciscan Assemblage; |. General geology, ancient and
modern analogues, and implications for hydrothermal
convection at oceanic spreading centers: Economic
Geology, v. 77, no. 3, p. 519-540.

Crittenden, M.D., Jr., 1964, Manganese, in U.S. Geological
Survey and Nevada Bureau of Mines, Mineral and water
resources of Nevada: Nevada Bureau of Mines Bulletin
65, p. 113-119.

Cyprus Geological Survey Department, 1982, Mineral re-
sources map of Cyprus: scale 1:250,000.

Elderfield, H., Gass, |.G., Hammond, A., and Bear, L.M., 1972,
The origin of ferromanganese sediments associated with
the Troodos Massif of Cyprus: Sedimentology, v. 19, no.
1-2, p. 1-19.

Gass, |.G., 1968, Is the Troodos Massif of Cyprus a fragment of
Mesozoic ocean floor?: Nature, v. 220, no. 5162, p. 39-
42.

Geological Survey of Japan, 1978, Geological map of Japan:
scale 1:1,000,000.

Georgiou, E., Christodoulou, E., and Panayiotou, A., 1981,
Report on the investigations of the umber quarry licences
of the Umber Corporation of Larnaca, Ltd.: Cyprus,
Geological Survey Department report G/MR/001/81, 16

p.

Green, S.H., 1945, Manganese deposits of the Olympic Penin-
sula, Washington: Washington Division of Mines and
Mining Report of Investigations 7, 45 p.

Hein, J.R., Koski, R.A., and Yeha, Hsueh-wen, 1987, Chert-
hosted manganese deposits in sedimentary sequences of
the Franciscan Complex, Diablo Range, California, in
Hein, J.R., ed., Siliceous sedimentary rock hosted ores
and petroleum: New York, Van Nostrand-Reinhold, p.
206-230.

Hewett, D.F., 1966, Stratified deposits of the oxides and carbon-
ates of manganese: EconomicGeology, v. 61, no. 3, p.
431-461.

—-1972, Manganite, hausmannite, braunite—features,
modes of origin: Economic Geology, v. 67, no. 1, p. 83-
102.

Hunt, C.B., McKelvey, V.E., and Wiese, J.H., 1942, The Three
Kids manganese district, Clark County, Nevada: U.S.
Geological Survey Bulletin 936-L, p. 297-319.

Huntting, M.T., Bennett, W.A.G., Livingston, V.E., and Moen,
WS., 1961, Geologic map of Washington: Washington
Division of Mines and Geology, scale 1:500,000.

Jennings, C.W., Strand, R.G., and Rogers, T.H., compilers,
1977, Geologic map of California: California Division of
Mines and Geology, California Geologic Data Map Series
2, scale 1:750,000.

Koski, R.A., 1986, Descriptive model of volcanogenic Mn, in
Cox, D.P., and Singer, D.A., eds., Mineral deposit mod-
els: U.S. Geological Survey Bulletin 1693, p. 139.

Lewis, G.E., and Straczek, J.A., 1955, Geology of south-central
Oriente, Cuba: U.S. Geological Survey Bulletin 975-D, p.
171-336.

Magill, E.A., 1960, Manganese deposits of the Olympic Penin-
sula, Washington: U.S. Bureau of Mines Report of Inves-
tigations 5530, 82 p.

Mitchell, A.H., and Bell, J.D., 1973, Island-arc evolution and
related mineral deposits: Journal of Geology, v. 81, no. 4,
p. 381-405.

Mosier, D.L., 1986, Grade and tonnage model of volcanogenic
Mn, in Cox, D.P., and Singer, D.A., eds., Mineral deposit
models: U.S. Geological Survey Bulletin 1693, p. 139-
141.

Namson, Jay, Chyi, M.S., Crerar, D.A., Feigenson, M.D., and
Williams, L., 1981, Evidence for a hydrothermal origin of
manganiferous cherts from the Franciscan assemblage
[abs.]: Geological Society of America Abstracts with
Programs, v. 13, no. 2, p. 99.

Park, C.F., Jr., 1941, Manganese resources of the Olympic
Peninsula, Washington: A preliminary report: U.S. Geo-
logical Survey Bulletin 931-R, p. 435-457.

——-1942, Manganese deposits of Cuba: U.S. Geological
Survey Bulletin 935-B, p. 75-97.

——-1946, The spilite and manganese problems of the Olympic
Peninsula, Washington: American Journal of Science, v.
244, no. 5, p. 305-323.

Robertson, A.H.F., 1975, Cyprus umbers: Basalt-sediment
relationships on a Mesozoic ocean ridge: Geological
Society of London Journal, v. 131, pt. 5, p. 511-531.

Rodda, P., and Band, R.B., 1966, Geology of Viti Levu: Geologi-
cal Survey of Fiji Report G.S. 432, scale 1:250,000.

Simons, F.S., and Straczek, J.A., 1958, Geology of the manga-
nese deposits of Cuba: U.S. Geological Survey Bulletin
1057, 289 p.

Singer, D.A., 1975, Mineral resource models and the Alaskan
Mineral Resource Program, in Vogely, W.A., ed., Mineral
materials modeling—a state-of-the-art review: Baltimore,
John Hopkins University Press, p. 370-382.

Singer, D.A., 1984, Mineral resource assessments of large
regions: Now and in the future, in Geological Survey of
Japan, ed., U.S.-Japan joint seminar on resources in the
1990's: Tokyo, Japan, Earth Resources Satellite Data
Analysis Center, v. 2, p. 32-40.

Skiba, W.J., 1964, Geological studies in southwest Viti Levu:
Geological Survey of Fiji Memoir 1, 56 p.

Snyder, W.S., 1978, Manganese deposited by submarine hot
springs in chert-greenstone complexes, western United
States: Geology, v. 6, no. 12, p. 741-744.

Taliaferro, N.L., and Hudson, F.S., 1943, Genesis of the manga-
nese deposits of the Coast Ranges of California, in Man-
ganese in California: California Division of Mines Bulle-
tin 125, p. 217-275.

Trask, P.D., Wilson, I.F., and Simons, F.S., 1943, Manganese in
California—a summary report, in Manganese in Califor-
nia: California Division of Mines Bulletin 125,p. 51-215.

Watanabe, Takeo, Yui, Shunzo, and Kato, Akira, 1970, Meta-
morphosed bedded manganese deposits of the Noda-

20 Models of Volcanogenic Manganese Deposits in Oceanic Environments


Descriptive and Grade-Tonnage Models of
Volcanogenic Manganese Deposits
in Oceanic Environments—a Modification

By Dan L. Mosier and Norman J Page

Abstract

Four types of volcanogenic manganese deposits,
distinguished on the basis of geologic, geochemical, and
geophysical characteristics, appear to result from a combin-
ation of volcanic and hydrothermal processes related to hot-
spring activity inoceanicenvironments. We compare these four
deposit types, here called Franciscan, Cuban, Olympic
Peninsula, and Cyprus, with respect to host rocks, associated
rocks, minerals, deposit shape, dimensions, volume, tonnage,
grade, and mineral-deposit density (number of deposits per unit
area).

Franciscan-type deposits occur in obducted oceanic ridge
and backarc marginal-basin environments, are associated with
chert, shale, and graywacke around the margins of mafic
volcanic centers, and have a median tonnage of 450 t and
median grades of 36 weight percent Mn and less than 5.1
weight percent Fe. Cuban-type deposits occur in island-arc
environments, are associated with tuff and limestone around
domal structures or intrusions inferred to be volcanic centers,
and have a median tonnage of 6,400 t and median grades of 39
weight percent Mn and less than 4.4 weight percent Fe.
Olympic Peninsula-type deposits occur in obducted oceanic
midplate settings, are associated with argillaceous limestone,
argillite, and graywacke around mafic volcanic centers
(seamounts or islands), and have a median tonnage of 340 t and
median grades of 35 weight percent Mn and less than 6.5
weight percent Fe. Cyprus-type deposits occur in the same
tectonic environments as Franciscan type but are associated
with basalt, mart, chalk, silt, and chert off the ridge-axis position
and have a median tonnage of 41,000 tand median grades of 33
weight percent Fe and 8 weight percent Mn. All these deposits
are thin ellipsoids, concordant to the host rocks, but Cyprus- and
Cuban-type deposits are larger than Franciscan- and Olympic
Peninsula-type deposits. Except for Cyprus-type deposits,
which are manganiferous iron (umber) deposits composed of
hydrated iron and manganese oxides, all volcanogenic
manganese deposits contain manganese oxides, silicates, and
carbonates.

Mineral-deposit densities, along with grade and tonnage
information, are useful for estimating the number, size, and
grades of these deposits in resource assessments.

INTRODUCTION

This investigation modifies the descriptive (Koski, 1986)
and grade-tonnage (Mosier, 1986) models for volcanogenic
manganese deposits formed on the sea floor. The original
descriptive model represents deposits varying in geologic
characteristics, and the original grade-tonnage model yields a
median tonnage (47,000 t) and median grade (42 weight
weight weight percent Mn) that may not be indicative of those
for deposits with similar geologic attributes in particular
tectonic environments, such as a midoceanic ridge. In this
report, we differentiate volcanogenic manganese deposits on
the basis of geologic characteristics and lithotectonic
environments, and from these observations, we develop new
models that may represent more accurately the different types
of deposits and that may be applicable to resource assessment
and exploration. We propose four types of submarine
volcanogenic manganese deposits and compare them with
respect to tonnage, grade, size, shape, volume, mineralogy,
host rocks, associated rocks, and mineral-deposit density
(number of deposits per unit area). For each deposit type, on
the basis of the criteria in the descriptive model, we present
grade and tonnage models, as well as mineral-deposit
densities, for quantitative, probabilistic resource estimations.

Volcanogenic manganese deposits consist of stratabound
lenses of manganese oxides, silicates, and carbonates in
volcanic-sedimentary sequences. Manganese ore bodies may
have either a proximal or a distal relation to volcanic rocks.
Beneath the lenses, the rocks may be altered to clay, chlorite,
and zeolite, and veined by quartz, calcite, barite, hematite, and
manganese minerals. The genetic implication is that these
deposits are formed by hydrothermal solutions emanating
from ocean-floor vents as a result of volcanic processes.
Taliaferro and Hudson (1943) suggested that the manganese
deposits found in chert and basalt of the Franciscan Complex,
Calif., were derived from submarine hydrothermal activity,
similar to the processes occurring at oceanic spreading
centers. Recently, these deposits have been compared to the

Introduction 1


F Cu cy
09

0.8
O07 -
0.6

05 -

i

0.4

03

PROPORTION OF DEPOSITS

0.2

a1

1 1 1

00034 00045  .0064
poi

0.0
0000001 = .000002 000025 -0004
-0000004 -000006 .0001

.0063 A 1.6 25
0016 025 4 6.3

TONNAGE, IN MILLIONS OF METRIC TONS

Figure 18. Cumulative frequencies of tonnages and median tonnages for four types of volcanogenic
manganese deposits: Cu, Cuban; Cy, Cyprus; F, Franciscan; O, Olympic Peninsula.

1.0

oy roc! |
0.9
0.8F
0.7F

0.6

T T T T T

0.5

0.4

0.3

PROPORTION OF DEPOSITS

0.2F

oi y
8
0.0 1

3536 39
i i

1 i i 1

(0) 10 20 30 40

50 60 70 80 90 100

Mn GRADE, IN WEIGHT PERCENT

Figure 19. Cumulative frequencies of manganese grade and median manganese
grades for four types of volcanogenic manganese deposits: Cu, Cuban; Cy,
Cyprus; F, Franciscan; O, Olympic Peninsula.

Application of the Models and Constraints on Genetic Models

7


APPENDIX A

DEPOSIT TYPE Franciscan-type volcanogenic manganese. MODEL 24 c-1

DESCRIPTION Lenses and stratiform bodies of manganese oxide, carbonate, and silicate in chert
associated with sedimentary and mafic volcanic rocks. Genesis related to volcanogenic processes.

GENERAL REFERENCES Trask and others (1943), Koski (1986).

GEOLOGIC ENVIRONMENT

Rock Types Chert, shale, sandstone, graywacke, jasper, tuff, basalt, and serpentine. Thin- and thick-
bedded red or white chert and jasper are the predominant host rocks. Tholeiitic and alkaline volcanic

rocks.

Textures White, red, brown, and green chert in thin-bedded or massive lenses, commonly with shale
partings. Some of the chert contains radiolarians.

Age Range Paleozoic to Jurassic.

Depositional Environment Sea-floor hot spring, deep water in a zone of oceanic upwelling at or near
a continental margin.

Tectonic Setting(s) Oceanic ridges and rifted marginal basins (backarc setting) obducted onto a
continental margin.

Associated Deposit Types Hot-spring mercury, silica-carbonate mercury, podiform chromite.
DEPOSIT DESCRIPTION

Mineralogy Abundant psilomelane, pyrolusite, rhodochrosite, hausmannite, braunite, and neotocite;
minor bementite, wad, rhodonite, inesite, pyrochroite, tephroite, ganophyllite, dannemorite, py-
roxmangite, stilpnomelane, spessartine, pyrophanite, nsutite, manganite, cryptomelane, jacobsite,
manjiroie, Mn-phlogopite, todorokite, piedmontite, hollandite, manganocalcite, bimnessite, alleghanyite,
galaxite, and alabandite.

Texture/Structure Fine-grained massive crystalline aggregates, botryoidal, colloform in bedded and
lensoid masses; veinlets and disseminations.

Alteration Primary carbonates and silicates altered to oxides; some silicates altered to carbonates.
Ore Controls Sufficient structure and porosity to permit sub-sea-floor hydrothermal circulation and
sea-floor venting; redox boundary at sea-floor/seawater interface around hot springs; supergene

enrichment to upgrade Mn content.

Weathering Strong development of secondary manganese oxides (psilomelane, pyrolusite, todorokite,
bimnessite, manganite) at the surface and along fractures.

Geochemical Signatures Mn, Fe, Cu, Hg, and Ba.

Examples Ladd mines, USCA (Hein and others, 1987); Noda-Tamagawa, JAPN (Watanabe and
others, 1970; Yamada and others, 1980).

Appendixes 25


Table 5. Information level and geologic, geochemical, and geophysical characteristics of volcanogenic manganese desposits

Information Geologic, geochemical, and geophysical characteristics
Franciscan type Cuban type Olympic Peninsula Cyprus type
type
Environments obducted onto a continental margin (tectonic environment)
1
Midoceanic ridge or inner- | Island arc Ocean basin Midoceanic ridge or
arc basin (mid plate setting) inner arc basin
Volcanic-rock types present

2 Basaltic volcanic rocks Mafic to silicic Basaltic volcanic Basaltic volcanic

related to ophiolites volcanic and volcani- rocks related to rocks related to
clastic rocks seamounts ophiolites
Associated rock types present
3 Interbedded tuffaceous Thick wedges of Interbedded fine- Interbedded marl,
limestone or limy tuff graywacke, sandstone, grained argillaceous chalk, silt, and
shale, and chert limestone, gray- chert
wacke, and argillite
Changes in depositional environment or evidence for cessation of volcanism
Rapid clastic sedimen- Volcanism followed Thick pillow basalt, Thick pillow-

4 tation (turbidites) by carbonate-rich tuff, and agglomerate | basalt sequences
followed by slower rate sedimentation followed by clastic with fault-con-
of sedimentation (thin- thin-bedded trolled depres-
bedded chert) sedimentary rocks sions, followed

by sedimentation
Local tectonic position of deposition
Margins of volcanic Presence of domal Absence of ultramafic linor amount of
5 centers structures, or intrusions | and mafic rocks of sulfide mineraliza-
inferred to be volcanic ophiolitic origin, tion, suggesting
centers suggesting a mid- off-ridge-axis
plate position position
Evidence of hydrothermal circulation systems
Mn carbonates and Pervasive and fracture- Veinlets of Mn ‘e oxide in
silicates, along with controlled montmor- silicates, quartz, fractures and

6 quartz and rare calcite, rillonite, zeolite, non- specular hematite, breccias
aragonite, and barite tronite, barite, calcite, calcite, barite, and
in fractures and breccias and chlorite alteration zeolites in fractures

and joints
Geochemical anomalies
7 Mn, Fe, Cu, Hg, Ba Mn, Fe, Cu, Ba Mn, Fe, Cu, Hg, Ba in, Fe, Ni, Cu,
Zn, Co
Presence of manganese deposits, prospects, or occurrences
Mn oxide and Mn Mn oxide and Mn silicate and |Absence of Mn

8 carbonate-oxide silicate assemblages oxide assemblages silicate or
assemblages dominant dominant dominant carbonate assem-

blages

Application of the Models and Constraints on Genetic Models

19


of a manganese silicate or carbonate mineral in Cyprus
deposits; an amorphous manganese hydroxide is the only
major manganese mineral in the umbers of Cyprus deposits.
All the deposit types contain manganese oxides or
hydroxides, either as primary or secondary minerals. For
example, hausmannite and manganite may be primary
minerals in some deposits (Hewett, 1972), and psilomelane
and pyrolusite are common secondary products of
weathering.

Cuban deposits differ from both Franciscan and Olympic
Peninsula deposits in the paucity or absence of manganese
carbonate minerals, such as rhodochrosite or manganocalcite.
Cuban deposits characteristically have manganese silicate-
oxide assemblages, and braunite is the most common silicate
mineral; however, the most common silicate mineral in
Franciscan and Olympic Peninsula deposits is neotocite and
bementite, respectively (table 1), except in Japan, where it
appears to be braunite.

occa eene Reef limestone
Ses Sees Or Snes ce aes es ns Se es Se es os SS oS OS oe on OO os ee eo en ee ee eee
[os aS os Se Se OOO SS OO SS OO Os

i Bentonitic clay, argillite

‘chert, and gri

tine
<Fe-rich veins:

eee

Figure 14. Generalized model of a Cyprus-type deposit, based on the data of Constantinou and Govett

(1972) and Robertson (1975).

1.0 T T T

0.9F

0.8F

0.7F

0.6

O5-

0.4-

0.3-

PROPORTION OF DEPOSITS

0.2

O.1-F v
0011
i 1

0.0

041 1.8
iT i i j 1

000025 .0001 .0004 .0016 .0063 .025 1 4°16 63 25

TONNAGE, IN MILLIONS OF METRIC TONS
Figure 15. Cumulative frequency of tonnages for Cyprus-type deposits.

14 Models of Volcanogenic Manganese Deposits in Oceanic Environments


Table 2. Frequencies and percentages of host-rock types in the four types of volcanogenic manganese deposits.

[The value on the left side of each column is the number of times a rock type was hosting a deposit, and the value in parentheses on the right
is the percentage of the rock type calculated to 100 percent. Data are derived from type areas discussed in the text]

Franciscan Olympic
Ci t pi
Host rock type ban type Peninsula type Cyprus type
Rhyolite to andesite tuff 2.00 (0.37) | 65.14 (50.52) | 1.00 (1.02) :
Agglomerate ++: 433 (3.36) wee .
Rhyolite to andesite flow oot 441 (3.42) ote oot
Jasper 16.34 (3.06) | 27.49 (21.32) | 3.50 (3.57) -50 (0.55)
Limestone 33 (0.06) | 11.91 (9.24) 144.00 (44.90)} 1.00 (1.10)
Mudstone, shale, clay, or argillite | 36.34 (6.81) 8.83 (6.85) ] 3.00 (3.06)} 3.50 (3.85)
Marl 2.82 (2.19) see 9.30 (10.23)
Chert or radiolarite 441.50 (82.68) 400 (3.10) ue 5.00 (5.50)
Basalt or greenstone 24.00 (4.49) ote 46.50 (47.45) | 62.80 (69.09)
Chalk wee -e- 7.80 (8.58)
Serpentine 1.00 (0.19) 50 (0.55)
Gabbro -ee -50 (0.55)
Slate 2.00 (0.37) aa
Horfel 50 (0.09) wee
Glaucophane or mica schist 2.00 (0.37) see
Sandstone 8.00 (1.50) “ss wee wee
Total number of deposits 534.01 (99.99) | 128.93 (100.00) [98.00 (100.00) | 90.90 (100.00)
to) 50 METERS
LLL
Japan Cuba
3.2
Philippines 560
Fiji
0 1.4 Mexico
California Q45
013 "419 Turkey .
. Washington | Cyprus
Oregon California 8 %
Franciscan type Cuban type Olympic Cyprus
Peninsula type
type

Figure 4. Comparison of median length, width, and thickness for volcanogenic manganese deposits by region and type.
Length is vertical dimension, width is horizontal dimension, and thickness is number in center of or next to ellipse.
Dimensions of deposits are listed in table 3.

Models of Volcanogenic Manganese Deposits in Oceanic Environments


APPENDIX D

DEPOSIT TYPE Cyprus-type volcanogenic manganese. MODEL 24 c-4

DESCRIPTION Lenticular bodies of umber (manganiferous Fe-rich sedimentary rock) overlying
pillow-basalt flows at the base of a sedimentary sequence. Genesis is related to volcanogenic processes.

GENERAL REFERENCE Constantinou and Govett (1972).
GEOLOGIC ENVIRONMENT

Rock Types Umber, silt, grit, conglomerate, radiolarian chert, pillow basalt, red jasper, chalk, and marl;
tholeiitic volcanic rocks.

Textures Basalt shows pillow structures and brecciation.

Age Ranges Late Cretaceous.

Depositional Environment Deep to shallow marine basin near continental margin.

Tectonic Setting(s) Interarc-basin and midoceanic-ridge settings obducted onto a continental margin.
Associated Deposit Types Cyprus massive sulfide deposits.

DEPOSIT DESCRIPTION

Mineralogy Amorphous manganese hydroxide, goethite, and maghemite. No discrete manganese
mineral has been determined.

Texture/Structure Massive, structureless, extremely fine grained lenticular masses.

Alteration Pyrite, where present, alters to iron oxides.

Ore Controls Commonly occurs in depressions on the surface of basalt flows, in interbeds between
basalt flows, in fault-controlled depressions on volcanic breccia, and in lowermost parts of the covering
sedimentary-rock sequence.

Weathering Important for manganese enrichment.

Geochemical Signatures Mn, Fe, Ni, Cu, Zn, and Co.

Examples Troulii, Drapia, and Skouriotissa, CYPS (Georgiou and others, 1981).

28 Models of Volcanogenic Manganese Deposits in Oceanic Environments GPO 585-045/78032


proportion of deposits. A logarithmic scale is used for
tonnages, and an arithmetic scale for grades. Each dot
represents one deposit, cumulated inversely in ascending
order. Smooth curves are plotted through the points, and
intercepts of the 10th, 50th, and 90th percentiles are drawn.
These smooth curves represent percentiles of a log-normal
distribution (except for grades) that have the same mean and
standard deviation as the observed data. For ease of compari-
son among deposit types, the cumulative-frequency plots for
each variable for all types are shown on a single diagram.

Host rocks for each deposit type were tested for frequency
of occurrence. A single rock type hosting a deposit was
counted as one. If more than one rock type hosts a deposit,
each type was counted asa fraction of the total number of rock
types hosting the deposit. The counts of each rock type then
were summed to give the frequency of the host-rock
occurrence in each deposit type. A special test was made for
Franciscan-type deposits in California to see whether
proximity to greenstone is significant. The deposits were
assigned to two groups, on the basis of whether or not
greenstone crops out within 1,600 m of the deposit.

Mineralogy was tested for the frequency of occurrence of
mineral assemblages in deposits and for the relative
abundance of individual minerals. In the first test, mineral
assemblages were counted and categorized into the following
groups: oxides (hydroxides), carbonate-oxides, silicate-
oxides, carbonate-silicate-oxides, and Fe-Mn material. The
counts for each group were then converted into percentages.
Inthe second test, individual minerals were ordered according
to their relative abundance in each deposit, using the method
of Bliss (in press). This test was done only for those regions
where the order of abundance of the minerals is reasonably
well known. For each mineral, individual ranks were
summed, and a median rank was calculated.

55
50f 1
45f 7

40 ¢ Inplace ore

35 F | Shipping ore 1
307 7

25F 4

20r 4
A

MEAN Mn GRADE, IN WEIGHT PERCENT
INPLACE Mn GRADE, IN WEIGHT PERCENT

15
Figure 1.

Mineral-deposit density is defined as the number of
deposits per unit area. Using the method of Bliss and others
(1986), deposit densities were determined for those regions
where exploration has been extensive, where the locations of
deposits are known, and where detailed geologic maps of an
appropriate scale are available. A closely spaced net of
gridlines was placed over the geologic map, and only the rock
unit containing deposits was point-counted to determine the
area (in square kilometers). The total number of deposits was
divided by this area to give the mineral-deposit density (in
number of deposits per square kilometer). Calculated for a
deposit type, this value can be used to estimate the number of
undiscovered deposits expected within a given unexplored
area, assuming that the unexplored area is permissive for such
deposits and geologically similar to that described for the
deposit type.

MANGANESE MODELS

The characteristics of each of the four types of volcano-
genic manganese deposits are discussed below. Generally,
these four types occur in different depositional environments
(fig. 2), and each type shows particular characteristics,
whether in petrography, mineralogy, size, or shape. Both
Franciscan and Cyprus deposits are believed to have formed
on the ocean floor at the rock-seawater interface by solutions
emanating from fractures at or near a midoceanic ridge or in
arifted basin. Olympic Peninsula deposits formed similarly
on or around seamounts in an ocean basin. Cuban deposits are
associated with felsic to intermediate island-arc volcanic
tocks and are thought to have formed from sea-floor hot
springs in a shallow marine environment.

50 T T T
y = 13.4622 + 0.304% R =0.17 n = 62
a
40 ooF a 4
30
20
10F ooo 4
B o®
0 n 1 1
20 30 40 50 60

SHIPPING Mn GRADE IN WEIGHT PERCENT

Ranges of manganese grade for inplace and shipping ore (A), and inplace versus shipping manganese grade for Francis-

can-, Cuban-, and Olympic Peninsula-type deposits (B ). Horizontal line in figure 1A is overall mean for both types of ore; circles
are the means for both types of ore; error bars, 10. Sloping line in figure 1B is curve of best fit to data points, described by equation.

n, number of data points; R, correlation coefficient.

Methodology 3


hydrothermal mounds actively forming at oceanic ridges
(Snyder, 1978; Namson and others, 1981; Crerar and others,
1982). A similar origin has been proposed for the manganese
deposits associated with limestone and tuff formed in an
island-arc environment in the Oriente Province, Cuba (Park,
1942; Simon and Straczek, 1958; Mitchell and Bell, 1973);
for the deposits associated with basaltic seamounts in the
Olympic Peninsula, Wash. (Park, 1942; Cady, 1975); and for
the manganiferous iron deposits in pillow basalt, derived from
an oceanic ridge, in Cyprus (Gass, 1968; Elderfield and
others, 1972). Because of detailed geologic studies in these
four areas, we have chosen these deposits to represent four
models of volcanogenic manganese deposits formed in
oceanic environments.

Acknowledgments

We thank Donald A. Singer and James D. Bliss, both of the
U.S. Geological Survey, for discussions on some of the
analytical techniques used in this report; Gary B. Sidder, Ted
G. Theodore, and George A. Havach, all of the U.S.
Geological Survey, for their helpful suggestions; and Andreas
Panayiotou of the Geological Survey Department, Cyprus,
for valuable information on the manganese deposits of
Cyprus.

METHODOLOGY

Submarine volcanogenic manganese deposits were as-
signed to one of four types, here called Franciscan, Cuban,
Olympic Peninsula, and Cyprus (hereafter for brevity referred
to in this report as “Franciscan deposits,” “Cuban deposits,”
“Olympic Peninsula deposits,” and “Cyprus deposits”),
named from the type locality that best represents each model.
Franciscan deposits occur in chert associated with basalt
derived from midoceanic ridges. Cuban deposits occur in
pyroclastic rocks derived from island-arc volcanism. Olym-
pic Peninsula deposits occur in limestone and basalt that are
present as seamounts in midplate settings. Cyprus deposits
are umbers associated with basalt, clay, marl, and chert on the
flanks of midoceanic ridges.

The method of collecting and grouping the data used in
this report follows that outlined by Cox and Singer (1986).
First, the descriptive (and genetic) models for submarine vol-
canogenic manganese deposits were made by describing the
attributes of deposits occurring in distinct lithotectonic envi-
ronments. Second, the grade-tonnage models were made for
each of the deposit types, and those characteristics were
compared. Third, other quantitative properties, such as size,
shape, mineralogy, host rock, and mineral-deposit density,
were analyzed for differences.

Data extracted from the literature were tabulated under the
following headings: name, length, width, thickness, volume,
tonnage, grade, minerals, geologic environment, and com-

ments. A total of 913 deposits were classified into the four
deposit types. Care was taken to include deposits from regions
where the lithologic and tectonic environments are well estab-
lished; these data are currently being compiled.

The term “deposit” refers to a single lens or bed of man-
ganese ore as it presently occurs. For example, a bed or lens
separated completely by a fault was counted as two deposits.
However, where tiny pods or nodules are closely strung out
along a bed, or thin bands of ore and rock alternate, these
materials were considered collectively as a single deposit.
The number of pits, open cuts, or underground workings
generally indicates the number of deposits present. Deposits
considered to be float or ina landslide were excluded from the
final analysis.

Dimensional properties of deposits were either taken di-
rectly from previous reports or measured from maps.
“Length” refers to the maximum dimension of the ore body,
“width” to the intermediate dimension, and “thickness” to the
minimum dimension. We used maximum values for lengths
and widths, and average values for thicknesses; however, for
some deposits, we utilized maximum values for thicknesses
when average values could not be determined. Deposit
volumes representellipsoids (in cubic meters). Tonnage isthe
total premining weight (in metric tons) of the deposit, includ-
ing either inplace reserves or production plus inplace reserves
after production. Owing to the availability of the data, only
production or shipping ore is reported for some deposits; such
data tend to cause an underestimate of the mean tonnage.
Grades for manganese and iron include the average inplace
grade of the deposit, the shipping grade (generally more than
37 weight percent Mn), or the analytical grade of grab or chip
samples. Shipping and analytical grades are used only in the
absence of average deposit grades; such data tend to cause an
overestimate of the average grade of the deposit (fig. 1).

For each mine reported, the number of deposits was deter-
mined. For some deposits, individual ore bodies were re-
ported, giving the dimensions, tonnage, and average manga-
nese grade (by production and reserves); for others, these
parameters had to be estimated from less detailed descrip-
tions. Where estimates were not possible, those variables
were left blank in the tabulation. Also, for each deposit, host
rock and mineralogy were determined from the literature. No
assumptions concerning host rock or mineralogy were made;
if these parameters were not reported, they were left blank in
the tabulation.

The tonnage, grade, volume, length, width, and thickness
data for the four deposit types were tested for differences (at
the 5-percent-confidence level), using the analysis-of-
variance F-ratio test. Comparative diagrams were made for
the logarithms of volume, length, width, and thickness, and
for the arithmetic values of iron grade, showing the median
values and the 95-percent-confidence intervals for each de-
posit type. Inverse cumulative-frequency plots for tonnage,
manganese grade, and iron grade were constructed, using the
method of Singer (1975, 1984). The horizontal axis shows
these variables, while the vertical axis shows the cumulative

2 Models of Volcanogenic Manganese Deposits in Oceanic Environments


0.9

0.8

0.7

0.6

0.5

0.4

0.3

PROPORTION OF DEPOSITS

0.2

0.41

0.0

deposits.

1.0

aru

1 1 i 1 1

30 40 50 60 70

T T
n=7
|
80 90 100

Mn GRADE, IN WEIGHT PERCENT
Figure 16. Cumulative frequency of manganese grades for Cyprus-type

0.9

0.8

O7L

0.5

PROPORTION OF DEPOSITS

02,

01

0.0

O6L

04-E

O3-

v

26 fh é 1 1 1

to)

10

20

30 40 50 60 70
Fe GRADE, IN WEIGHT PERCENT

80 90 100

Figure 17. Cumulative frequency of iron grades for Cyprus-type deposits.

Comparison of Models by Properties

15


Table 1. Abundances of manganese minerals, in order of median rank

[Cyprus-type deposits are not shown because of the paucity of manganese minerals]

Median Franciscan type Cuban type Penireula ioe
rank California Oregon Cuba Mexico Turkey California Washington
1 Psilomelane, | Pyrolusite, Psilomelane |Braunite Pyrolusite, Psilomelane, Bementite,
Mn-Fe oxide | manganite, psilomelane, Mn chert hausmannite
wad thodochrosite
2 Rhodochrosite, |Rnodonite Pyrolusite,  |Pyrolusite, Hausmannite, |Rhodonite, Neotocite
pyrolusite, bementite, | cryptomelane, | praunite, pyrolusite,
Mn chert, neotocite, bementite cryptomelane | Mn calcite,
neotocite, braunite, bementite
hausmannnite, rancieite
braunite
3 Bementite, Psilomelane |Manganite, |Neotocite, Manganite, Neotocite, Inesite,
thodonite inesite pyrolusite, thodonite thodochrosite | Mn-Fe oxide,
manganite Mn calcite
4 Wad fee Wad se ee Rhamsdelite Braunite Rhodochrosite,
thodonite,
pyrolusite
es ee Celadonite [7 --- Wad,
spessartine,
braunite
a a es Pumpellyte [------[----

minor minerals; all primary minerals have been completely
oxidized. A typical carbonate-silicate-oxide assemblage is
thodochrosite, neotocite or bementite, and manganese oxides.
A carbonate-oxide assemblage contains rhodochrosite and
manganese oxides, and a silicate-oxide assemblage consists
of bementite or neotocite and manganese oxides. In
Franciscan deposits in Japan, the assemblages are similar to
those in California, except that braunite is the primary silicate
mineral. In similar deposits in Oregon, manganite is an
abundant oxide mineral. Traces of chalcocite, cuprite,
malachite, native copper, pyrite, and cinnabar occur in some
deposits. Quartz, chalcedony, hematite, calcite, siderite, and
barite are the main gangue minerals,

Host rock.— Thepredominant host rock of the Franciscan
deposits is chert, commonly red, white, or green, in 83 percent
of the deposits; thin-bedded chert predominates over massive
(thick bedded) chert, some of which contains radiolarians.
Other host rocks include greenstone, jasper, sandstone, shale,
slate, serpentine, limestone, and schist (table 2). In the Coast
Ranges of California, only 46 percent of 461 deposits occur
within 1,600 m of an outcrop of greenstone.

Shape and size.—Ore bodies of Franciscan deposits range
in shape from thin and narrow to wide and ellipsoidal (fig. 4).
Lengths range from 1.2 to 1,200 m, widths from 0.6 to 450m,
and thicknesses from 0.01 to 14 m. For 111 deposits, the
median length is 33 m, the median width 12 m, and the median
thickness 1.5 m (table 3). Deposits in California, Oregon, and
the Philippines are thin and linear, whereas those in the
Philippines are significantly longer and thicker. Deposits in

Japan, which have the largest median length and width, form
thin ellipsoidal masses.

Tonnage, grade, and volume.—For 181 Franciscan de-
posits, the median tonnage is 450 t, and the median manganese
grade 36 weight percent Mn (figs. 5,6). The mean iron grade
for 23 deposits is 5.1 weight percent Fe. The median volume
for 210 deposits is 75 m} (fig. 7; table 3).

Mineral-deposit density —Deposit densities were calcu-
lated only for Franciscan deposits in the Franciscan Complex,
Calif., and the Kitakami Mountains, Japan. In California,
1.9x107 deposit per square kilometer (table 4) occurs in rocks
mapped as the Franciscan Complex on the 1:750,000-scale
geologic map of Jennings and others (1977). In the Kitakami
Mountains, Japan, areas were delineated on the basis of the
manganese-bearing Carboniferous to Cretaceous units, as
mapped on a 1:1,000,000-scale geologic map (Geological
Survey of Japan, 1978). Permian and younger rocks have
generally similar deposit densities, ranging from 1.9x10? to
6.7x107 deposit per square kilometer, whereas Carboniferous
rocks have a deposit density an order of magnitude smaller
(3.8x10%) (table 4).

Cuban Type

The manganese deposits occurring in the Cobre Forma-
tion, Oriente Province, Cuba, best represent the Cuban type.
These deposits occur along certain beds in a pyroclastic
sequence or along pyroclastic beds in limestone. The pyro-
clastic rocks range in composition from dacite to basalt. The

Manganese Models 5


Tamagawa mine, in Tatsumi, Tatsuo, ed., Volcanism and Sawa, Toshiaki, Hattori, Hitoshi, Satoh, Hiroyuki, and

ore genesis: Tokyo, University of Tokyo Press, p. 143- Aikawa, Tadayuki, 1980, Mines summary report, v. 1,
152. North-east Japan:Geological Survey of Japan Report 260,
Yamada, Keiichi, Sudo, Sadahisa, Sata, Takeo, Fujii, Noriyuki, p. 162.

References Cited 21


Descriptive and Grade-Tonnage Models
of Volcanogenic Manganese Deposits in
Oceanic Environments—a Modification

By DAN L. MOSIER and NORMAN J PAGE

A characterization of four types of

submarine volcanogenic manganese deposits,
based on descriptive and grade-tonnage
models for such deposits in the

Franciscan Complex of California,

Cuba, the Olympic Peninsula, and Cyprus

U.S. GEOLOGICAL SURVEY BULLETIN 1811


host rock ranges in age from Cambrian to Pliocene. The shape
of the ore bodies is tabular and elliptical, and they are mostly
stratabound and conformable to bedding, occurring as fine- to
coarse-grained massive layers, nodules, disseminations, vein-
lets, and stringers containing predominantly psilomelane,
pyrolusite, braunite, bementite, and neotocite. The adjacent
pyroclastic rocks may be altered to montmorillonite, chlorite,
and zeolite. Hematitization iscommon (Simons and Straczek,
1958). Appendix B contains a descriptive model for Cuban
deposits in the form of Cox and Singer (1986). A generalized
model based on the data of Simons and Straczek (1958) is
shown in figure 8.

Cuban deposits are found in the Oriente Province, Cuba;
Viti Levu, Fiji; the Shasta district and Sierra Nevada, Calif.;
Mexico; Panama; Honduras; Turkey; Argentina; Iran; Nova
Scotia; Great Britain; France; and Algeria. In the Oriente
Province, Cuba, these deposits are closely associated with
structural domes (Simons and Straczek, 1958).

Mineralogy.—The predominant mineral in the Cuban de-
posits are silicates and oxides; carbonates are absent. Psi-
lomelane is the most abundant oxide mineral, followed by
pyrolusite and manganite. Braunite, neotocite, and bementite
are the most abundant silicate minerals (table 1). Less
abundant are rancieite, orientite, wad, inesite, piedmontite,
hausmannite, and rhodonite. Rhodochrosite is rare; it is
reported from only two deposits in California and Turkey.
Hematite, magnetite, pyrite, chalcopyrite, cuprite, malachite,

100,000
w 10,000F
fo
we
¥ t
=
cS}
S 1,000F
(o)
Zz
ul
2
5
Oo 100
° ‘
10
Franciscan Cuban Olympic Cyprus
type type Peninsula type
type

Figure 7. Median volumes and 95-percent-confidence intervals
(vertical bars) for four types of submarine volcanogenic
manganese deposits.

0.9

0.4-

0.3

PROPORTION OF DEPOSITS

0.2F

O.1-

0.0

0 10 20 30 40

50 60 70 80 90

100

Mn GRADE, IN WEIGHT PERCENT

Figure 6. Cumulative frequency of manganese grades for Franciscan-type deposits.

8 — Models of Volcanogenic Manganese Deposits in Oceanic Environments


Table 3. Median values for dimensional extent and volume of ore bodies by region and deposit type.

[nQwt), number of deposits by length, width, and thickness; n(v), number of deposits by volume. Discrepancies
between these two numbers are due to the availability of reported data. Cu, Cuban; Cy, Cyprus; Fr, Franciscan; O,
Olympic Peninsula]

Region Length Width | Thickness n(Iwt) Volume n(v)
(m) (m) (m) (m’)
California (Fr) 26.4 8.7 14 69 78.7 164
Oregon (Fr) 12 33 13 6 46 7
Japan (Fr) 89.7 57.0 Ll 20 14 44
Philippines (Fr) 54.8 1d 3.2 5 703.0 5
Turkey (Cu) 400.0 150.0 5.6 1 4,930.0 1
California (Cu) 5.9 24 19 3 53.5 5
Cuba (Cu 211.8 68.6 2.0 34 | 13,243.0 41
Mexico (Cu) 75.2 28.0 2.8 7 5,728.0 7
Fiji (Cu) 175 10.1 5.6 2 40.2 3
Washington (O) 13.5 47 15 41 1,239.0 41
Cyprus (Cy) 133.4 36.1 3.9 26 | 6,902.4 26
Type
Franciscan 33.3 12.0 15 11 75.0 210
Cuban 99.0 38.3 2.1 60 6,039.5 75
Olympic Penin. 13.5 47 1.5 41 40.2 41
Cyprus 133.4 36.1 3.9 26 | 6,902.4 26
1.0 -—hagy a TT
0.9
osr
2 07F
ao
2 06h
Ww
a
6 05
2
So
Ee 04F
8
Q 03F
«
a
02
0.1
000013 00045
0.0 n i 14 y_.015) fh Oo An)
.0000004 .000006 0001 .0016 025 4
-000002 .000025 .0004 .0063 A 1.6

TONNAGE, IN MILLIONS OF METRIC TONS

Figure 5. Cumulative frequency of tonnages for Franciscan-type deposits.

Manganese Models 7


Franciscan Type

The manganese deposits occurring in the Franciscan
Complex of the Coast Ranges, Calif., best represents the
Franciscan type. These deposits are commonly hosted in
massive or thin-bedded chert with or without shale partings,
and range in age from Paleozoic to Tertiary. The ore deposits
are generally thin, elliptical bodies, concordant with bedding,
and composed of massive and disseminated psilomelane,
pyrolusite, rhodochrosite, hausmannite (Mn,O,), braunite
(3Mn,0,-MnSiO,), neotocite (MnSiO;H,0), and other minor
manganese oxides and silicates. Colloform and botryoidal
shapes are common. Near the surface, the primary carbonates
and silicates are commonly altered either partially or com-
pletely to oxides. In some deposits, manganese carbonates
and silicates, as well as quartz, calcite, aragonite, and barite,
occur in fractures and breccias beneath the main ore body.
Some deposits have been metamorphosed to greenschist fa-
cies (Trask and others, 1943). Franciscan deposits are found

in California, Oregon, Nevada, Japan, New Zealand, Austra-
lia, the Philippines, Costa Rica, Malaysia, New Caledonia,
Yugoslavia, Afghanistan, Pakistan, and elsewhere in Europe
and Asia. Appendix A contains a descriptive model for
Franciscan deposits in the form of Cox and Singer (1986).
Associated with the chert are mafic volcanic rocks (green-
stone), tuff, serpentine, and graywacke. A generalized model
based on the data of Crerar and others (1982) is shown in
figure 3.

Mineralogy.—In the Franciscan Complex of the
California Coast Ranges, the predominant manganese
minerals are psilomelane, rhodochrosite, pyrolusite,
neotocite, hausmannite, braunite, and bementite
[Mn,Si,O,,(OH),,] (table 1). Assemblages of only
manganese oxides occur in 70 percent of these deposits,
followed by carbonate-silicate-oxide assemblages (14
percent), carbonate-oxide assemblages (10 percent), and
silicate-oxide assemblages (4 percent). A typical manganese
oxide assemblage is psilomelane, pyrolusite, wad, and other

Franciscan type Olympic
Cuban type Peninsula type

Franciscan type

Cuban type Cyprus type

Sea level

Oceanic
crust

Midplate

seamount trench

Oceanic ridge Upper mantle

Subduction

Backarc basin

Continental

Island arc
crust

Figure 2. Original tectonic settings of four types of submarine volcanogenic manganese deposits.

-: Conglomerate: :

Basalt

Fractures

Figure 3. Generalized model of a Franciscan-type deposit, based on the data of

Crerar and others (1982).
4

Models of Volcanogenic Manganese Deposits in Oceanic Environments


contains an area with geology permissive for the occurrence
of a particular deposit type. Different levels of geologic
information are available for different areas, and so, some
adjustments can be made to the boundaries of tracts as the
level of geologic information increases. Geologically, geo-
chemically, and geophysically derived characteristics for
volcanogenic manganese deposits at different levels of infor-
mation that can be used to constrain and refine boundaries of
tracts are listed in table 5. This list is far from complete and
could include rapid burial to preserve the deposits, deep or
long-term weathering to enrich the deposits, and so on.

Once tracts have been identified, their areas, in combina-
tion with mineral-deposit density measured using the same
criteria in table 4, can be used to estimate the number of
deposits in the tracts. Such estimates should be adjusted with
respect to the number of known deposits and their exploration
history to estimate the number of undiscovered deposits in the
tracts. By analogy, half of the total number of undiscovered
deposits should have tonnages and grades below the median,
and half above the median, of the appropriate tonnage and
grade model. The size and volume distributions in this report,
in combination with local geologic knowledge, should also
help in the design of drilling programs to locate additional
deposits.

Although the purpose of this report is not to derive genetic
models for volcanogenic manganese deposits, the informa-
tion compiled and analyzed herein imposes constraints on

40
5 ‘
a 30 - 4
9
fo
wo
a b 4
io}
g 20 - 4
zZ
ul L 4
3
Oo 10h 4
D
“te
te)
Franciscan Cuban Olympic Cyprus
type type Peninsula type
type

Figure 20. Median iron grades and 95-percent-

confidence intervals for four types of volcanogenic
manganese deposits.

such models. In general, there appears to be a combination of
volcanic and hydrothermal processes akin to hot-spring activ-
ity that produces different manganese deposits in at least four
oceanic environments.

Similar processes have been postulated to be active in
continental environments (Hewett, 1966, fig. 7). For ex-
ample, the Three Kids deposit, Nev., is in a section of Pliocene
tuff and sedimentary rocks that were deposited in a shallow
lake or playa. Manganese is believed to have been carried into
the basin by hot springs rising along marginal faults (Hunt and
others, 1942). The lens of wad and minor manganite is about
915 m long, 458 m wide, and a maximum of 15 m thick; it
contains 7.4 million t of ore grading 12.5 weight percent Mn
and 1 weight percent Fe (Crittenden, 1964). Associated
manganiferous veins or active hot springs may have a sili-
ceous or calcareous apron rich in manganese. Some deposits
are rich in base and precious metals (Ohe, Japan) or tungsten
(Golconda, Nev.). Although this report focuses on the various
types of submarine-hot-spring manganese deposits, the con-
tinental-hot-spring manganese deposits, which evidently
belong to the same general class of volcanogenic manganese
deposits, should be investigated similarly as more data be-
come available.

REFERENCES CITED

Bliss, J.D., in press, Mineralogic and grade-tonnage information
on low-sulfide Au-quartz veins: U.S. Geological Survey
Open-File Report.

Bliss, J.D., Menzie, W.D., Orris, G.J., and Page, N.J, 1986,
Mineral deposit density—a useful tool for mineral-re-
source assessment [abs.], in Sachs, J.S., ed., USGS re-
search on mineral resources—1987 program and ab-
stract: U.S. Geological Survey Circular 995, p. 6.

10,000

1,000- 4

100 f

CONTAINED Mn METAL, IN METRIC TONS

Franciscan Cuban Olympic Cyprus
type type Peninsula type
type

Figure 21. Median contained manganese metal and 95-
percent-confidence intervals for four types of volcanogenic
manganese deposits.

18 Models of Volcanogenic Manganese Deposits in Oceanic Environments


APPENDIX B

DEPOSIT TYPE Cuban-type volcanogenic manganese. MODEL 24 c-2

DESCRIPTION Tabular bodies of manganese oxide and silicate lying along certain beds of a pyroclas-
tic sequence or along pyroclastic beds in limestone. Genesis is related to volcanogenic processes.

GENERAL REFERENCES Simons and Straczek (1958), Koski (1986).
GEOLOGIC ENVIROMENT

Rock Types Pyroclastic rocks, tuffaceous limestone, and volcaniclastic and volcanic rocks of basaltic to
dacitic composition; calc-alkaline volcanic rocks.

Textures Fine- to coarse-grained massive or bedded limy and fossiliferous tuff; agglomerate contains
rounded to angular fragments, as much as 15 m long, set in a tuff matrix; limestone is tuffaceous,
massive to thin bedded.

Age Range Cambrian to Pliocene.

Depositional Environment Sea-floor hot spring, shallow marine in island-arc environments.
Tectonic Setting(s) Island-arc setting obducted onto a continental margin.

Associated Deposit Types Kuroko massive sulfide deposits.

DEPOSIT DESCRIPTION

Mineralogy Psilomelane, pyrolusite, braunite, bementite, neotocite are the most common; manganite,
rancieite, wad, orientite, inesite, piedmontite are less abundant; hausmannite and rhodonite are rare.

Texture/Structure Fine- to coarse-grained massive layers, nodules, irregular masses, patches, dissemi-
nated fragments, pockets, veinlets, and stringers, mostly conformable to bedding and stratabound.

Alteration Andesitic and basaltic tuff, altered to montmorillonite clay minerals, chlorite, and zeolite;
hematitization.

Ore Controls Sufficient structure and porosity to permit sub-sea-floor hydrothermal circulation and
sea-floor venting; redox boundary at sea-floor/seawater interface around hot springs; supergene
enrichment to upgrade Mn content.

Weathering Strong development of secondary manganese oxides at the surface and along fractures.

Geochemical Signatures Mn, Fe, Cu, and Ba.

Examples Quinto and Ponupo mines, CUBA (Simons and Straczek, 1958); Nambu mine, FIJI (Skiba,
1964).

26 Models of Volcanogenic Manganese Deposits in Oceanic Environments


IV Contents

20. Diagram showing mean Fe grades and 95-percent-confidence intervals for four types
of volcanogenic manganese deposits 18

21. Diagram showing median contained manganese metal and 95-percent-confidence
intervals for four types of volcanogenic manganese deposits 18

TABLES

. Abundances of manganese minerals, in order of median rank 5

2. Frequencies and percentages of host-rock types in the four types of volcanogenic
manganese deposits 6

3. Median values for dimensional extent and volume of ore bodies by region and deposit
type 7

4. Mineral-deposit densities of volcanogenic manganese deposits by rock unit and
region 9

5. Information level and geologic, geochemical, and geophysical characteristics of

volcanogenic manganese deposits 19

APPENDIXES

A. Franciscan-type volcanogenic manganese deposits 25

B. Cuban-type volcanogenic manganese deposits 26

C. Olympic Peninsula-type volcanogenic manganese deposits 27
D. Cyprus-type volcanogenic manganese deposits 28


0.8 F

O7F

0.6

05 F

0.4-F

03fF

PROPORTION OF DEPOSITS

0.2-

O1F

00021
i it 1 1

0064
1 fl 19

0.0
-000002 -000025 .0004 0063 A
.000006 01 6

}001 .001 025

TONNAGE, IN MILLIONS OF METRIC TONS

Figure 9. Cumulative frequency of tonnages for Cuban-type deposits.

0.9

0.8

O.7F

0.4-F

0.3

PROPORTION OF DEPOSITS

0.2F

O1-

0.0

n =84

v as
2 39 63
po

4t_

Figure 10.

10 20 30 40 50 60 70 80
Mn GRADE, IN WEIGHT PERCENT

90 100

Cumulative frequency of manganese grades for Cuban-type deposits.

Comparison of Models by Properties

"W


ook
og b a]

O7b a 4
0.6L - 4

05

04-

03,

PROPORTION OF DEPOSITS

02

O1- v

.000003 .00034
1 1 1 1 1 1

a
0.0 l 1 1.035 | 1
0000001 000002 000025 0004 0063 1 1.6
0000004 000006 -0001 0016 025 4

TONNAGE, IN MILLIONS OF METRIC TONS

Figure 12. Cumulative frequency of tonnages for Olympic Peninsula-type deposits.

0.9-

0.8- 7
O.7F a 4
0.6F 4 4

O.5-

0.4-

PROPORTION OF DEPOSITS

O.1F v

0.0 i 1 !
0 10 20 30 40 50 60 70 80 90 100

Mn GRADE, IN WEIGHT PERCENT

Figure 13. Cumulative frequency of manganese grades for Olympic Peninsula-
type deposits.

Comparison of Models by Properties 13


CONTENTS

Abstract 1

Introduction 1
Acknowledgments 2
Methodology 2

Manganese

models 3

Franciscan type 4
Cuban type 5
Olympic Peninsula type 10
Cyprus type 12

Comparison of models by properties 12
Mineralogy 12
Host rock 16
Shape, dimensions, and volume 16
Tonnage 16
Grade 16
Contained metal 16
Mineral-deposit density 16

Application

of the models and constraints on genetic models 16

References cited 18

FIGURES

1

15-19.

Plots of median inplace and shipping manganese grades, and of inplace versus
shipping manganese grade, for Franciscan-, Cuban-, and Olympic Peninsula-
type deposits 3
Schematic illustration of original tectonic settings of four types of submarine
volcanogenic manganese deposits 4
Generalized model of a Franciscan-type deposit 4
Diagram comparing median length, width, and thickness for volcanogenic
manganese deposits by region and type 6
Plot of cumulative frequency of tonnages for Franciscan-type deposits 7
Plot of cumulative frequency of Mn grades for Franciscan-type deposits 8
Diagram showing median volumes and the 95-percent-confidence intervals for four
types of volcanogenic manganese deposits 8
Generalized model of a Cuban-type deposit 10
Plot of cumulative frequency of tonnages for Cuban-type deposits 11
Plot of cumulative frequency of Mn grades for Cuban-type deposits 11
Generalized model of an Olympic Peninsula-type deposit 12
Plot of cumulative frequency of tonnages for Olympic Peninsula-type deposits 13
Plot of cumulative frequency of Mn grades for Olympic Peninsula-type
deposits 13
Generalized model of a Cyprus-type deposit 14
Plot of:
15. Cumulative frequency of tonnages for Cyprus-type deposits 14
16. Cumulative frequency of Mn grades for Cyprus-type deposits 15
17. Cumulative frequency of Fe grades for Cyprus-type deposits 15
18. Cumulative frequency of tonnages and median tonnages for four types
of volcanogenic manganese deposits 17
19. Cumulative frequency of Mn grades and median Mn grades for four
types of volcanogenic manganese deposits 17

Contents Ill


APPENDIXES



DEPARTMENT OF THE INTERIOR
DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY
Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988

For sale by the

Books and Open-File Reports Section
U.S. Geological Survey

Federal Center, Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Mosier, Dan L.
Descriptive and grade-tonnage models of volcanogenic man-
ganese deposits in oceanic environments —a modification.

(U.S. Geological Survey Bulletin 1811)
Bibliography: p.
Supt. of Does. no.: 1 19.3:1811

1. Manganese ores. |. Page, Norman J, 1939-_. Il. Title.
I, Series: United States. Geological Survey. Bulletin 1811.
QE75.B9 no. 1811 557.38 87-600462

[TN490.M3} [553.4°629'09162]


APPENDIX C

DEPOSIT TYPE Olympic Peninsula-type volcanogenic manganese. MODEL 24 c-3

DESCRIPTION Tabular, conformable lenses of manganese oxides and silicates in or between argil-
laceous red limestone and pillow basalt. Genesis is related to volcanogenic processes.

GENERAL REFERENCES Green (1945), Magill (1960), Cady (1975), Koski (1986).
GEOLOGIC ENVIRONMENT

Rock Types Pillow basalt and red argillaceous limestone. Associated tuff, agglomerate, argillite, and
graywacke. Alkaline or tholeiitic volcanic rocks.

Textures Basalt flows have massive and pillow structures; limestone is very fine grained, argillaceous,
and siliceous; argillite is calcareous and ferruginous.

Age Ranges Eocene or older.

Depositional Environment Deep to shallow marine on or near basaltic seamount or islands;
sea-floor hot spring.

Tectonic Setting(s) Ocean basin with seamounts and volcanic islands (midplate setting),
obducted onto a continental margin.

DEPOSIT DESCRIPTION

Mineralogy Bementite, hausmannite, neotocite are common; inesite, manganite, rhodochrosite,
thodonite, pyrolusite, manganocalcite are less abundant; braunite, wad, tephroite, manganophyllite,
piedmontite, jacobsite, spessartine are minor.

Texture/Structure Finely crystalline massive lenses and layers (banding), spongy or colloform
layering of hausmannite, brecciation, nearly round microstructures to oolitic structures, algal structure or
fecal pellets.

Alteration Silicification, greenschist-facies metamorphism.

Ore Controls Sufficient structure and porosity to permit sub-sea-floor hydrothermal circulation and
sea-floor venting; redox boundary at sea-floor/seawater interface around hot springs; supergene
enrichment to upgrade Mn content.

Weathering Secondary manganese oxides (pyrolusite and manganite) are formed as oxidation products
of bementite or other manganese minerals; restricted to surface and along joints.

Geochemical Signatures Mn, Fe, Cu, Hg, and Ba.

Example Crescent mine, USWA (Magill, 1960).

Appendixes 27


Table 4. Mineral-deposit densities (number of deposits per square kilometer) of volcanogenic manganese deposits by rock unit and region.

Area Number of | Number of
Host Rock (km?) deposits deposits per
km?
Franciscan type
Franciscan Complex, California 23,655 453 0.019
Kitakami Mountains, Japan
Upper Jurassic to Lower Cretaceous sandstone, slate, chert 75 3 040
Permian to lower Mesozoic sandstone, slate, chert, limestone, basalt 1,048 70 067
Permian sandstone, slate, chert, limestone, conglomerate, basalt 2,241 42 019
Lower Carbonifcrou dstone, slate, limestone, basalt, andesite 530 2 0038
Cuban type
Cobre Formation, south-central Oriente, Cuba
Charco Redondo limestone member 197 16 081
Tuff, agglomerate, subordinate flows 927 93 10
Limestone 9 1 Al
Jasper 2 9 4.50
Total (includes other members not containing deposits) 1,197 119 10
Viti, Levu, Fiji
Suva Marl—marl, sandstone, limestone (Pliocene and Miocene) 81 1 O12
Navosa—andesite pyroclastic rocks, mudstone, limestone, conglomerate 254 1 0039
(Pliocene and Miocene)
Nandi Group—conglomerate, marl, limestone, andesite (Pliocene and 253 5 020
Miocene)
Singatoka—sandstone, mudstone, volcanic rock (Miocene) 316 4 013
Wainimbuka Trachyte—lithic tuff, lava, limestone (Miocene) 170 2 012
Numbuonamboto Volcanic Conglomerate—conglomerate, volcanic rocks
(Oligocene) 914 1 0011
Mount Gordon Subgroup—volcanic rocks, mudstone, limestone (Eocene) 735, 4 0054
Total 2,723 18 0066
Olympic Peninsula type
Olympic Peninsula, Washington
Pre-upper Eocene argillite and graywacke 686 9 013
Lower and middle Eocene basalt flows and breccias, limestone 2,909 100 034
Total 3,595 109 .030
Cyprus type
Troodos Complex, Cyprus
Upper Pillow Lavas 312 74 24
Radiolarite and marl 13 8.5 65
Clay 56 1S 027
Serpentine 4 1 016
Gabbro 185 5 .0027
Chalk and marl 1,334 5.5 0016
Total 1,964 91 046

native copper, and chalcocite are present in some deposits.
The main gangue minerals include quartz, chalcedony, jasper,
calcite, barite, opal, siderite, ankerite, chlorite, halloysite,
kaolinite, dolomite, feldspars, and biotite.

Host rock.—Rhyolitic, dacitic, and andesitic tuffs are host
rocks for the ore in 51 percent of Cuban deposits (table 2).
Tuff is a major host rock in all of the regions except Panama

and the Foothill belt of California, where jasper or chert is the
major hostrock. In Mexico, Cuba, Honduras, and Turkey, tuff
is a major host rock in at least 80 percent of deposits. In Fiji,
about half the deposits have tuff as a host rock. Lenses of
jasper in either tuff or limestone are a major host rock in 21
percent of Cuban deposits (table 2). In Panama, jasper is the
host rock for 65 percent of deposits; and in the Foothill belt of

Manganese Models 9


Host rock.—Of 98 Olympic Peninsula deposits, 47 per-
cent are hosted in basalt, 45 percent in limestone, and the rest
in tuff, jasper, and argillite (table 2). About a third of these
deposits occur in the contact between limestone and basalt. In
some of the limestone-hosted deposits, jasper lenses contain-
ing manganese were reported; however, jasper is not a major
host rock.

Shape and size —Ore bodies of Olympic Peninsula de-
posits are mostly thin, narrow ellipsoids. For 41 deposits, the
median length is 14 m, the median width 4.7 m, and the median
thickness 1.5 m (fig. 4; table 3). Lengths range from 0.9 to 366
m, widths from 0.3 to 152 m, and thicknesses from 0.2 to 8.5
m.

Tonnage, grade, and volume.—For 17 Olympic Penin-
sula deposits, the median tonnage is 340 t, and the median
manganese grade 35 weight percent Mn (figs. 12, 13). The
mean iron grade for 4 deposits is 6.5 weight percent Fe. The
median volume for 41 deposits is 40 m} (fig. 7; table 3).

Mineral-deposit density—The Olympic Peninsula,
Wash., has 3.0x10 deposit per square kilometer (table 4) in
an area limited by lower and middle Eocene basalt and
limestone and pre-upper Eocene argillite and graywacke, as
delineated on the 1:500,000-scale geologic map by Huntting
and others (1961). Most deposits are in lower to middle
Eocene rocks.

Cyprus Type

The manganese deposits occurring in the Troodos Com-
plex, Cyprus, best represent the Cyprus type. These deposits
generally are lenticular bodies of umber (manganiferous iron-
rich sedimentary rock) overlying pillow-basalt flows, which
are at the base of a sedimentary sequence. The umber is
massive, structureless, and extremely fine grained, composed
of goethite, maghemite, and an amorphous hydroxide of
manganese. Iron oxides also occur in fractures and breccias
beneath the umber. Umber deposits also occur in the Semail
region, Oman. Appendix D contains a descriptive model for

Cyprus deposits in the form of Cox and Singer (1986). A
generalized model based on the data of Constantinou and
Govett (1972) and Robertson (1975) is shown in figure 14.

Host rock—Most of the umbers in the Troodos Complex
are hosted in the Upper Cretaceous Upper Pillow Basalt (table
2). The umber is commonly overlain by various sedimentary
rocks, such as clay, marl, chalk, radiolarian chert, jasper, and
conglomerate.

Mineralogy.—No discrete manganese minerals have
been identified in the umbers, except for an amorphous
hydroxide. Goethite, maghemite, and rare pyrite and quartz,
compose the bulk of the ore (Constantinou and Govett, 1972).

Shape and size —Ore bodies of Cyprus deposits are thin,
wide ellipsoids. Lengths range from 10 to 968 m, widths from
5 to 387 m, and thicknesses from 0.5 to 33 m. For 26 deposits,
the median length is 133 m, the median width 36 m, and the
median thickness 3.9 m, (fig. 4; table 3).

Tonnage, grade, and volume—For 7 Cyprus deposits,
the median tonnage is 41,000 t, and the median grades 8
weight percent Mn and 33 weight percent Fe (figs. 15-17).
The median volume for 26 deposits is 6,900 m3 (fig. 7; table
3).

Mineral-deposit density—The Troodos Complex in
Cyprus has 4.6x 10 deposit per square kilometer, on the basis
of a 1:250,000-scale geologic map (Cyprus Geological
Survey Department, 1982). The most favorable host units are
the radiolarite and marl unit (6.5x10" deposit per square
kilometer) and the Upper Pillow Lavas (2.5x107 deposit per
square kilometer).

COMPARISON OF MODELS BY PROPERTIES
Mineralogy

Minerals among the four deposit types were compared by
relative abundance (table 1) and assemblage type. The most
significant difference among the deposit types is the absence

Figure 11. Generalized model of an Olympic Peninsula-type deposit, based on the data of
Park (1941, 1946).

12 Models of Volcanogenic Manganese Deposits in Oceanic Environments