METALS IN PENNSYLVANIAN BLACK SHALES FROM ORE FLUIDS NOT FROM SEAWATER

rmccoveneyr@umkc.edu

Illinois

METALS IN PENNSYLVANIAN BLACK SHALES

FROM ORE FLUIDS NOT SEA WATER

sphalerite in Stark shale, N MO

Zinc in Pennsylvanian black shales, Kansas City

Coveney 1979 Economic Geology

The Hushpuckney black shale, one of several metal-rich beds in Kansas City, contains >0.2 wt % Zn (>2000 ppm).

Typical metal values for metalliferous Pennsylvanian black shales, central USA

Mecca-type shales>20% Corg + <1% P2O5

Heebner-type shales <20% Corg + >1% P2O5

Zn 3350 3020 1620 1930Mo 1430 2260 80 86Ba 300 290 360 190

V 2850 3170 790 1050U 165 140 39 64

from Schultz & Coveney, 1991, Chemical Geology

Metalliferous Pennsylvanian black shales contain abundant Mo.

IllinoisBasin

Mo Pb

Tri-State

UMV

Cherokee Basin

Forest CityBasin

Arkoma Basin

Shale Basins and MVT Ore Districts

SalinaBasin

Hydrothermal dolomite + crystalline kaolinite* * or dickite (Schroeder & Hayes 1968; Keller 1988)

IllinoisBasin

Mo Pb

Tri-StateCherokee

Basin

Forest CityBasin

Arkoma Basin

SalinaBasin

Sphalerite in Mecca Qu. Shale equiv., central MO

1 cm

SalinaBasin

Sphalerite in Pennsylvanian black shales

Hushpuckney Shale Mbr, Kansas City MO

from Coveney 1979 Economic Geology

from Coveney 1984 C.R. IX ICC

Mecca Quarry Shale Mbr, Parke Co. IN

Sphalerite cleat in Stark Shale

sph

from JC Cobb, U IL dissertation, 1981

sph. cleat in coal

Sphalerite in coal

1 cm

sph

MVT mineralization occurs

in other beds as well.

MVT minerals, sphalerite and kaolinite in Pennsylvanian limestone. Stark KS

sphal

kaolinite

Bethany Falls limestone mbr., Stark, KS

hydrothermal passageways hydrothermal passageways

Bethany Falls Limestone, North Farlinville KS

Hydrothermal venting through root casts or burrows Bethany Falls Limestone

North Farlinville KS

back

kaolinite

sph

Kaolinite in hydrothermally corroded limestone

U.S. Hwy 36 Livingston Co MO

Keller’s SEMof sugary white kaolinite in Winterset limestone,

Kansas City MO

from W.D. Keller, 1988, Clays and Clay Minerals 36,154

Mineralized tubes with dolomite, calcite, sphalerite and kaolinite

Bethany Falls Limestone, Mound City KS

Mineralized tubes with hydrothermal dolomite, calcite, sphalerite and crystalline kaolinite

Dolomite veinlets I-470 Kansas City

ferroan dolomite+ tr sphal.

MVT minerals in Pennsylvanian limestone, Kansas City MO

barite

ferroan dolomite

wall of Central United Methodist Church

A mid-Mississippian to mid-Pennylvanian DRM or CRM paleopole

for Stark Shale fits with syngenetic magnetism

Kawasaki et al. 2007 Geophysical Journal International

Log-Log plots Mebl sh vs. Mes.w.from HD Holland Econ. Geol. 1979

Mineralization of black shales has been attributed to sea water* but this conclusion depends on log-log plots that minimize deviations from the

central trend.*Brongersma-Sanders 1966 Geol. Rundschau;

Heckel 1977 AAPG Bulletin; Holland 1979 Economic Geology

x for molybdenum in shales and muds

Mecca Quarry shale 1500 ppmCarioca Trench 150Black Sea 77 Kau Bay, Indonesia 100 average black shale 100 average shale 3

Turekian and Wedepohl, 1961; Holland 1979, 1984; Calvert 1990; Middelburg 1990; Dean et al. 1999; Zheng et al. 2000 GCA;

after Coveney, Goebel & Ragan 1987 Economic Geology

Th for primary fluid inclusions in sphalerite; calcite dates (yellow)

251 Ma

66 Ma136 Ma

39 Ma

Zn & Pb ore deposition

53-96o

65-12218-24%

o

NaCl65-122

18-24% o

NaCl65-122

18-24%

o

NaCl

oil

251 Ma

Pennsylvanianblack shale deposition

~290-251 Ma 73-8110%

o

NaCl

66 Ma

52-730%

o

NaCl

39 Ma

73-84o

53-800-11%

o

NaCl53-80

0-11% o

NaCl53-80

0-11% o

NaCl

oil

137 Ma

modern

<52 C 0-23%

o

NaCl

0 Ma

Alleghanian orogeny etc.

100200 0 Ma

Laramide Orogeny

300 Ma

late calcitedeposition

from Coveney et al 2000, Geology

Chronology for MVT ores, petroleum migration, regional tectonics, and black shales

Sources of metals for shales

Key Facts

• Zinc, Mo and other metals are widespread in Pennsylvanian shales.

• MVT minerals are ubiquitous throughout the central US craton in Paleozoic strata.

• Hydrothermal sphalerite occurs in shales, limestones, and coals of the US craton.

• Ores formed during the late Paleozoic.• Hydrothermal fluids traversed the region for long

periods.

Zn in shale from sea water????

• No. • More likely the Zn for sphalerite in the shales

came from the same source as the Zn in the MVT ores, having been transported by regional flow of basinal brines.

Hydraulic head ca. 300-250 Ma

Ouachita Mtns

Ap

pal

ach

ian

sA

ncestral R

ocky M

tns

A chronology for mineralization from basinal brines in the U.S. Midcontinent

• Early venting of hydrothermal fluids to Pennsylvanian seas and sediments with deposition of trace MVT ore and gangue minerals in accumulating Paleozoic sediments and rocks.

• Shales, mainly gray, sealed hydrothermal systems. • Continued hydrothermal activity plugged minor passageways and

led to formation of major ore deposits. • Dates on calcite gangue show that sporadic migration of basinal

brines continued for >100 million years.• Even today basinal brines from the Rockies reach central MO.• Hydrothermal basinal brines were the sources of metals for black

shales.

THANK YOU!

Metals in Midwestern Pennsylvanian shales did not come from sea water.