(Click on thumbnail image for an expanded view.)
Base metal sulfide mineralization.
Late-stage calcite replacing nonplanar (saddle) dolomite.
Note the abundant pyrite associated with the calcite and dolomite. OH3267
core, Strayer #1 well, Allen County, OH, 1230.3 ft.
A. Calcite replacing nonplanar (saddle)
dolomite. Although the large, almost white crystal on the right side
of the SEM photo exhibits the characteristic morphology of saddle
dolomite, it's lighter color in the backscattered electron mode means
that it's composition is different than the adjacent saddle dolomites
in the picture. The EDS spectrum shown in B shows calcium excess in
the crystal. Trenton Formation, OH 3479, Anderson well, Hancock Co.,
OH, 1337.8 ft.
B. EDS spectra of the crystal shown
Authigenic quartz replacing anhydrite in the Trenton Formation,
Anhydrite and quartz replace nonplanar (saddle) dolomite
and fill a large vug in the Trenton Formation in the subsurface of northwestern
Authigenic quartz partially filling a small vug in the
Black River Formation, Gray #1 well, Steuben County, NY, 7803 ft.
Supergene mineralization in the Black River Formation in
the subsurface of south-central NY. Gray #1 well, 7799.9 ft., Steuben
A. Bitumen coats a crystal of delafossite,
a copper-iron oxide that commonly occurs as a secondary mineral near
the base of the oxidized zone of copper deposits. Black crystals of
delafossite fill many small vugs in the Grey well core (it appears
white in this backscattered electron photomicrograph due to the high
atomic number of the copper and iron).
B. and C. show
the location of EDS analysis in this sample and the EDS spectra for
the white mineral.
Nonplanar (saddle dolomite fills this small vug in the
Black River Formation (Gray #1 well, Steuben County, NY, 7803 ft.). White
specks throughout the SEM photo are anhydrite.
Opal partially fills a small vug in peloidal limestone
in the Black River Formation in the subsurface of north central Pennsylvania.
This sample is from a zone about 70 ft. above an extensively dolomitized
section in the well. Identification of the white mineral as opal is based
on its isotropic behavior under crossed polars and its index of refraction
less than epoxy. Bayles #1 well, Bradford County, Pa, 12,300 ft.
Bitumen filling intercrystalline pore space in dolostone, Grey #1 well, Steuben County, NY, 7803 ft.
Bitumen filling intercrystalline pore space in dolostone, Whiteman #1 well, Chemung County, NY, 9531 ft.
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