11) via listric detachment faults, with brittle-ductile transitions on the footwall from
chloritic breccia to semi-ductile mylonite, fanning dips in syn-extensional upper-plate conglomerate units, domino-style upper-plate faults, and consistent angles of 50-70 degrees between detachments and bedding in conglomerate units (Seranne and Seguret 1987; Howard and John 1987; Lister and Davis 1989; Spencer and Reynolds 1989, 1991; Dickinson 1991).
These anomalously older ages maybe related to one or both of: (1) recoil effects due to the presence of K-free
chloritic phases in the altered samples that are synchronous with zeolite formation (Kontak 2000), or (2) incorporation of excess argon during post-eruptive alteration attending zeolite formation.
A 2 X 3 X 4-meter zone in the lower workings has produced the blocky tabular crystals for which the locality is famous, as well as unusual crystals elongated on the a axis, with {001} and {102} termination faces; slender twinned prisms with "feathered" terminations; highly elongated prismatic crystals measuring to 8 cm with "stepped" terminations and associated with chloritic and byssolitic quartz; flattened and slightly curved, smaller crystals nearly identical to those found in Copper Mountain's Jumbo #4 mine; one or two black, nearly opaque, flat, dime-sized, pseudo-hexagonal tablets; and unusual fans and aggregated fans of bi-colored "jackstraw" crystals, some of which penetrate, or are penetrated by, single prismatic crystals and crystal clusters of heavily included quartz.
The intact portion of the pocket--the part we muck out each year--produced slender, prismatic but mostly broken epidote associated with the mountain's largest and perhaps most pleasing green chloritic quartz crystals.
PLS13-055 intersected three radioactive intervals within sheared, graphitic,
chloritic, sulfide-bearing metapelitic gneiss, including two discrete narrow intervals of off-scale radioactivity.
The chemical composition corresponds to the distinction between dominantly talcose and dominantly chloritic ore, and to the amount of barren inclusions (unaltered rock: residual dolomite, pegmatite and mica schist).
Footwall rocks (Cambrian): The footwall consists of pegmatite and calc-silicate gneiss overlain by a few thrust outliers of mica schist or aluminosilicate formations in contact with the chloritic mineralization.
Another scepter quartz, this one from Winterstock, Furka, Switzerland, sits on a
chloritic matrix about 10 X 10 cm; the quartz crystal measures 3 X 10 cm and has a pale purple amethystine head.
The local series is composed of the metamorphic rocks, mostly sericite-phyllites,
chloritic and amphibolitic schists.
The early "feldspar-quartz-mica phase" of Thoreau (1928) cropped out as a
chloritic breccia and enlarged the network of fissures in the Kakontwe.
Andreas also showed me a gorgeous deep yellow-green
chloritic fishtail titanite 5 cm long, which at first I assumed to be from Pakistan or perhaps from some remarkably beneficent Alp, but no, it is so far the only piece taken from a locality to watch for: Gamsberg.
