Post on 29-Dec-2015
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.