VMS deposits are commonly associated with regionally developed iron- and (or) manganese-rich metalliferous sediment and chert
developed at the same time-stratigraphic horizon as the massive sulfide deposits.
Folk, "Exogenous carbonaceous microstructures in Early Archaean cherts
and BIFs from the Isua Green-stone Belt: Implications for the search for life in ancient rocks," Precambrian Research, vol.
Caption: Billions of years ago, localized hydrothermal activity, not globally warm oceans, heated and altered this South African chert
(rocks in the foreground) that formed on the seafloor.
Rhyolite, slightly coarser than the cherts
and chalcedonies, also became relatively more prominent in C2, especially within the tool assemblage.
Brookite, the orthorhombic trimorph of [TiO.sub.2], occurs in fine, doubly terminated, deep reddish brown crystals in chert
cutting Hale Creek, Trinity County, California.
More than 12,000 years ago, local natives started to quarry chert
from a small Alibates-capped hill within the Canadian River Valley, and tribes continued to quarry the colorful chert
for weapons and tools into historic time.
Both the Shepherds Bush and the Spotted Dog Prospects are topographically dominated by a ridge of outcropping chert
and ironstone, with zones of brecciation, silicification and quartz veining along the strike of this unit.
Key words: geochemical analysis, energy dispersive X-ray fluorescence; Mackenzie Inuit, Dene, Kuukpak, lithic raw material procurement, quarry sites, Thunder River chert
, oral history
Raw materials include banded light, dark grey and patinated cherts
, but white quartzite predominates.
Bedrock consists of limestone, sandstone, shale, chert
and mafic igneous rocks (Selkregg, 1974).
The gravel portion of the deposits are dominantly composed of chert
commonly containing Paleozoic fossils of crinoids, brachiopods, corals, bryozoans, gastropods, stromatolites, stromotoporids, and rare trilobites.
The name New Harmony Group was proposed by Becker & Droste (1978) to include the Grassy Knob Chert
, Backbone Limestone, and Clear Creek Chert