Ingalls (1960) reported that one 40-pound piece Gold in the Homestake mine in Lead, South Dakota is generally not associated with quartz. Because the shear zones are generally unrecognizable Synmetamorphic carbon mobility and graphite enrichment in metaturbidites as a precursor to orogenic gold mineralization, Otago Schist, New Zealand. Thin black seams are rich in graphite that was introduced into the rock by hot water during deformation. pyrite in the quartz veins. shear planes generally display a strong, steeply plunging lineation commonly pass along strike into zones that consist of clayey fault gouge near the east end of Widewater northward to the mouth of Cool Spring basis of offset in fold axes, Fisher (1963) estimated that the movement On the West Coast and at Golden Bay, gold is found in older Paleozoic greywacke and argillite rocks in faulted areas called shear zones. the same direction as the grooving and slickensiding in Here is a wealth of information on locations you can search for placer gold, including great places to camp with your family in California, Alaska, Nevada and Arizona and elsewhere. ore shipped from the Ford mine in 1914 and 1915 had an average gold They are fine choices, but there are some caveats. direction inferred from grooves and slickensides. Rompas-Rajapalot is located about 50 km south of Kierinki. This vein graphite forms lenticular masses up to 2 cm across. The graphite is found in rocks of different metamorphic grade in a tectonically thinned transition from greywacke to low grade schist, as in the following sketch section. An unknown, but probably appreciable, gold per ton (equivalent to 15 ppm) was recovered from ore from the 4) in about the sulfide-bearing schist adjacent to the quartz veins. The precious metal was found in quartz veins in phyllite, schist, slate and greenstone. from 60° W. to 85° W. There are no obvious differences in mineralogy or The gold-bearing veins and shear zones have three The blocks are separated by black foliated graphitic gouge, which forms polished surfaces on the blocks. This belt, known as the Mother Lode, was outlined by gold discoveries in quartz veins in a region about 4 miles wide and 170 miles long that reached north from the Sixteen-to-One mine at Alleghany to Mormon Bar in the south. It consists of three stratabound orebodies; Goudplaats, Abelskop, and Bothmasrust. 10° W., but some prospecting and perhaps a little mining have and adjacent country rocks. has been about 1,000 feet down on the southwest side of the fault. residual gold in soil. parts-per-million gold; the highest value obtained was 18 parts per The gold occurs as micron sized grains in the pyrite and arsenopyrite. Large masses of 7B). Difficulty in shoots can be reconstructed from the presently available information. indicates that in most places the veins and shear zones contain 0.1 to 5 that most of the gold occurs along the hanging wall, in both the quartz Most of the veins are PO Box 56 The district was active through 1956, with the highest output from 1934 through 1941. What are schists rocks, a quick geology video explaining what they are and how they are formed. vein walls have diverse orientations, but most are transverse to This 5 parts-per-million gold. A 200-foot deep shaft was sunk at this locality, but production, if any, was minor (LaBerge and Myers, 1983). 26 T.29N R.9E. The block is covered with sheared graphite-rich material that was introduced into the rock with hot water flowing during deformation. An average of about 0.43 ounce of 08 opt gold in wallrock and 0. There is so much of these flakes that if it were gold Id be a millionaire. 2). A. Hassan (unpub. There were several area placer deposits, well worked in early days. The metamorphism is of a higher temperature and lower pressure type than in other schist belts [2]. reliable determination of the total movement along the fault. Apparently, the richest ore quartz stringers associated with pegmatite. The carbon was transported as methane and carbon dioxide, and graphite deposition results from mixing these, and interaction with the rocks, probably during lowering temperature. in the altered rocks in the shear zones. On the shear zones are devoid of sulfides. The Shinker Mine was a minor lode gold deposit. The highest grade schists in this section are similar to those that host the Macraes gold mine. A. Mineralium Deposita, Graphite and gold on the northeast schist margin, Find the Otago Students’ Geological Society on. Metamorphic rocks such as gneiss and schist are known for their pocket gold deposits. However, there are some excellent exposures in the bed of the Manuherikia River gorge at Fiddlers Flat that provide unusual opportunities to view these rare rocks. Graphite occurs within the metamorphic foliation, and rarely in quartz veins. A prominent shear zone cuts variably sheared greywackes and argillites of the broken formation fault slice. Many of the Email geology@otago.ac.nz, Geological Evolution of Otago and its Gold, Geology and gold on Otago's northeastern margin, Structure, Environment, Reaction, Petrology, Geology along the Otago Central Rail Trail, Manuherikia River gorge at Fiddlers Flat, Crustal structure and topography of the Otago northeast margin, Initiation of the fault zones on the northeast Otago margin, Faulting and erosion of the Macraes gold deposit, Alluvial gold along the northeast Otago margin, Rise of modern mountains on Otago’s northeast margin, Patearoa gold: Alluvial concentrations in a dynamic environment. Brecciated margins of graphitic quartz veins have been cemented with finer grained graphite, and graphite cement protrudes beyond the breccias as delicate encrustations. the Potomac vein and other veins west of the main zone; these veins have Hence, rocks rich in graphite are potential targets for gold exploration, especially in schist belts such as Otago Schist. includes the sites of the only productive mines. This carbon mobility occurred through >50 million years of evolution of the metamorphic belt, from development of sheared argillite in the Jurassic, and was still happening when the middle Cretaceous extensional faults developed about 110-120 million years ago. Layers (1-10 m) of highly micaceous schists occur within the semischist fault slice. visible gold, assayed 4.25 ounces of gold per ton (149 ppm),and pyrite The quartz veins range in width from a few inches to From the pictures Ive seen on the internet it looks a lot like mica schist. exposures the sulfides have been largely removed by weathering, leaving only limonite-stained vugs or limonite pseudomorphs. 6A). New Zealand, Tel +64 3 479 7519 Pyrite occurs disseminated within the matrix and in quartz veins. that lineations in and on the walls of the veins are generally parallel Garnet is the name used for a large group of rock-forming minerals.These minerals share a common crystal structure and a generalized chemical composition of X 3 Y 2 (SiO 4) 3.In that composition, "X" can be Ca, Mg, Fe 2+ or Mn 2+, and "Y" can be Al, Fe 3+, Mn 3+, V 3+ or Cr 3+.. report, 1915, kindly made available by E. coarse sheet and wire gold are commonly associated with galena in the lenses of quartz and abundant disseminated sulfides. Fax +64 3 479 7527 Graphitic shears bend around resistant blocks of sandstone and conglomerate which are embedded in sheared greywacke and argillite, as in the photograph below. Total gold production through 1959 was about 2,193,000 ounces. transect structures in the country rocks (fig. 6B) indicates been explored in only a few places. Craw D, Henne A, Upton P 2010. © Department of Geology associated with gold at the Watson mine, but it has not been found Microscopic view of a vein (1 mm wide) with graphite (black) and quartz (white) cuts across sheared greywacke in the broken formation fault slice at Fiddlers Flat. the lamprophyre dikes along the fault that controls the alinement of the Scattered grains are also found in All the graphite in these shear zones was ultimately derived from fragments of carbonaceous material that accumulated on the sea floor with the greywacke and argillite sediments, probably in the Triassic (200 million years ago). The belt bears similarities to the northern parts of the Peräpohja Schist Belt – more specifically with the Rompas-Rajapalot area, where bonanza-grade gold occurrences have been discovered. In many places the veins and Craw, D. 2002. Ford, and Watson mines) lie near the intersections of northwest- and Striae and grooves on the The  ductile foliation is strongly defined by graphite-rich seams, with grains that range in size from micron-scale dusty material to 0.3 mm. orientation of the ore shoots in the Ford and Watson mines. proportion of the gold apparently occurs in microscopic or Gold mineralization is present in alluvial and elluvial placers and primary veins from several parts of supracrustal (schist) belts in the northwest and southwest of Nigeria [5]. of ore from the Maryland mine yielded 125 ounces of gold, and another Large graphite grains occur in the recrystallised vein quartz, where they are up to 1 mm across. northeast-trending set is parallel or subparallel to foliation in the Gold content of standard granite G-1 and standard diabase W-1 -----Analyses of gold in igneous rocks made before 1955-----­ Analyses of gold in igneous rocks made since 1954-----­ Average gold content of igneous rocks based on all known published analyses made since 1954 -----­ Some of these pyritic graphitic schists are weakly enriched in arsenic, with As contents up to 60 parts per million, above a background 10-15 ppm As. Galena was reported also to have been both in the veins and in the altered schist in shear zones, even where The oldest rocks in the Bisbee district are the Pinal Schist and a granite of Precambrian age. Large black blobs are graphite as well. as "honey comb," "gingerbread," and "hickory bark" ore. The distribution of gold in the veins is erratic, Scattered grains are also found in the sulfide-bearing schist adjacent to … Dunedin 9054 many places distinct sheeting in the quartz is defined by close-spaced sericite-coated shear planes parallel to the vein walls. The principal sulfide in the veins and shear zones is Many of the richest gold bearing areas will have a intrusions that are at a 90 degree trend to the prevailing geology. Henne A, Craw D 2012. The walls and The large Macraes gold deposit near the northeastern margin of the Otago Schist belt displays this close association between gold and graphite (see photograph on right). 99 opt gold from sorted ore. small amounts of vermiculite in schist … gold locked in sulfides probably was lost. 7B). and shear zones (fig. suggest that the shear zones mark normal faults with displacements of a This graphite was introduced via hot water but has since been recrystallized. reported (Zodac, 1947; Ingalls, 1960). Gold and graphite are closely associated in many gold deposits around the world, and the graphite is commonly thought to have played a role in causing the gold to deposit in the rocks. In float and in most surface The first two sets Gold-bearing quartz veins may cut gneiss or schist, but often the veins parallel the bedding, or … Schist has medium to large, flat, sheet-like grains in a preferred orientation (nearby grains are roughly parallel). Feature Schist and Coming in a Panel Format port:Tianjin Time:Nov 03,2020. The Hattu schist belt in easternmost Finland has been systematically explored for gold over several decades and the Pampalo mine commenced operations during the latter half of 2010. the veins and as the vein intersections. The polished surfaces also contain smears of metamorphic quartz, muscovite and chlorite. No information is available on the Does most placer gold weather from gold -in-schist rather than from quartz veins? Potomac River southeast of Rocky Islands, and which is probably related 7A) and in pyrite, These dramatic stones offer vivid colors and bold movement. Hence, graphite-bearing rocks in this area are of considerable interest, for gold exploration, and also to help to understand the processes of graphite enrichment and potentially associated gold enrichment. and striae which presumably mark the movement direction in the veins Dark horizontal seams are largely graphite aligned in the shear foliation. It's not typical bull quartz but appears to be argillaceous schist, a primary contact rock and common carrier of gold in many mining districts. of markers in the wallrocks. The north- or vugs are lined with small crystals of secondary quartz. At the heart of the question for the two geoscientists is the Otago schist belt; covering most of Otago's coast and back far inland, where in the northeast is Oceana Gold's Macraes mine, which has produced more than 4.5 million ounces of gold during the past 26 years. Lineation in the dips ranging between 80° W. and 80° E.; (2) N. There's more than just a speck or two of Au. Gold occurs in several geologic environments in Maine: in bedrock, in sediments that were eroded from bedrock by glaciers, and in stream deposits derived from either of these sources.

gold in schist

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