The Tungmuling Cassiterite-bearing Pegmatite,Nankang,S.Kiangsi

正 INTRODUCTION The Tungmuling, well known for its cassiterite deposits, is situated in the northern part of the Nankang district, S Kiangsi. It lies about 15 km SW of Shati, a station about 30 km NNW of the Kanhsien City along the Kanhsien-Chian Highway. The tin mine may be reached by following this     

The mineralogy of the Golden Sunlight gold-silver telluride deposit, Whitehall, Montana, U.S.A.

Summary The Golden Sunlight gold-silver telluride deposit, hosted primarily within the Mineral Hill breccia pipe (MHBP), is spatially related to a high-level, Late Cretaceous multiple intrusive, alkaline to subalkaline porphyry system. Base metal veins and manganese (rhodochrosite) mineralization occur up to 2km from the MHBP and form part of a regional mineral zonation pattern genetically related to a low-grade porphyry molybdenum system. Proterozoic rocks of the LaHood Formation and the informally named Bull Mountain Group host the MHBP and contain stratabound sulphides/ sulphosalts (up to 50% pyrite with minor to trace amounts of chalcopyrite, tennantite, pyrrhotite, sphalerite, galena, and molybdenite). Four periods of hypogene mineralization occur in the breccia pipe. Stages I and IV constitute ,99% of the mineralization; native gold (4–11 wt.% Ag), calaverite, tetradymite, tellurobismuthite, Se-bearing Bi sulphosalts (aikinite, lindströmite, krupkaite, gladite, bismuthinite, and ?benjaminite), tennantite (Zn, Fe, Te, and Bi varieties), coloradoite, melonite, galena (up to 6.7 wt.% Bi and 6.4 wt.% Se), stannite, chalcocite, and the rare mineral buckhornite are included in stage Ib. Minor amounts of base metals are present in stage II. Gold-silver tellurides (krennerite, petzite, sylvanite, and possibly the rare x-phase) developed in stage III whereas barite, fluorite, dolomite, magnesite, trace kaolinite, and sericite formed during stage IV. Utilizing the mineral assemblages in stage Ib, calculated values of logf Te₂ and logf S₂ range from -10.5 to -9.7, and -12.6 to -5.5, respectively.Ore forming components (e.g., Au, Ag, Te, Cu, Bi, Mo, and much of the S) were likely derived from the Late Cretaceous intrusive system with possible contributions from the Proterozoic host rocks.

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Mineralogie der Golden Sunlight Gold-Silber-Tellurid-Lagerstätte, Whitehall, Montana

Zusammenfassung Die Golden Sunlight Gold-Silber-Tellurid-Lagerstätte, die hauptsächlich im Brekzienschlot von Mineral Hill (Mineral Hill breccia pipe, MHBP) eingelagert ist, steht räumlich mit einem erzreichen, multi-intrusiven, alkalischen bis sub-alkalischen Porphyritsystem aus der Oberkreide in Beziehung. Erzadern und Mn-Mineralisation (Rhodochrosit) finden sich bis zu 2 km vom MHBP entfernt und sind Bestandteil einer regionalen Vererzung die genetisch zu einem erzarmen Mo-hältigen Porphyritsystem in Beziehung steht. Proterozoische Gesteine aus der LaHood-Formation und der inoffiziell benannten Bull Mountain Group umgeben den MHBP und enthalten schichtgebundene Sulfide und Sulfosalze (bis zu 50% Pyrit mit Neben- bis Spurenmengen von Kupferkies, Tennantit, Pyrrhotin, Zinkblende, Bleiglanz und Molybdänit).[Der Brekzienschlot zeigt vier Phasen hypogener Mineralisation. Stufen I und IV enthalten 99% der Mineralisation: gediegen Gold (4–11 Gew.% Ag), Calaverit, Tetradymit, Tellurobismuthit, Se-hältige Bi-Sulfosalze (Aikinit, Lindströmit, Krupkait, Gladit, Bismuthinit und ?Benjaminit) Tennantit (Zn-, Fe-, Te- und Bi-Varietäten), Coloradoit, Melonit, Bleiglanz (mit bis zu 6.7 Gew.% Bi und 6.4 Gew.% Se), Zinnstein, Chalcocit, sowie das seltene Mineral Buckhornit treten in Stufe Ib auf. Geringere Mengen von Buntmetallen kommen in Stufe II vor. Gold-Silber-Telluride (Krennerit, Petzit, Sylvanit und möglicherweise die seltene X-Phase) sind in Stufe III ausgebildet und in Stufe IV wurden Baryt, Flusspat, Dolomit, Magnesit, Spuren von Kaolin und Serizit gebildet. Unter Verwendung der Mineralassoziationen der Stufe Ib lassen sich Werte von logf Te₂ zwischen - 10.5 und - 9.7 und von logf S₂ zwischen - 12.6 und - 5.5 errechnen.[Die erzbildenden Komponenten (z.B. Au, Ag, Te, Cu, Bi, Mo und der Grossteil von S) stammen wahrscheinlich vom Intrusivsystem aus der Oberkreide, möglicherweise mit Beiträgen der proterozoischen Umgebung.[/ p]

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With 10 Figures     

The Cretaceous-Tertiary boundary on the cape fear arch,North Carolina,U.S.A.

Petrologic and faunal study of a 72.5 m continuous corehole drilled in southeastern North Carolina has provided an opportunity to study a relatively uninterrupted vertical sequence across the Cretaceous-Tertiary boundary. The following stratigraphic sequence occurs; upper middle Maastrichtian Peedee Formation, −65.8 m to −51.8 m below mean sea-level (BMSL), upper middle Maastrichtian Rocky Point Member of the Peedee Formation, −51.8 m to −27.4 m BMSL, and middle to upper (?) Eocene Castle Hayne Limestone, −27.4 m to −15.2 m BMSL (base of casing).The Peedee Formation consists of moderately indurated, very fine to fine, sandy foraminiferal biomicrite and sandy biomicrite. Silt-size zoned dolomite rhombohedra form up to 30% of the upper Peedee Formation and are most abundant where bioturbation is common. A diverse and well-preserved foraminiferal fauna indicates a middle to outer continental shelf environment.The Rocky Point Member conformably overlies typical Peedee Formation lithology and consists of well-indurated sandy, fossiliferous biomicrite that grades upward into sandy, pelecypod biomicrosparite, and finally pelecypod biomicrudite. The Peedee Formation and the Rocky Point Member represent an overall shallowing-upward sequence with the upper surface forming the Cretaceous-Tertiary boundary.The Castle Hayne Limestone disconformably overlies the Rocky Point Member and consists of lithoclast-bearing, bryozoan-molluscan biomicrudite grading upward into bryozoan biomicrudite. The Castle Hayne Limestone was deposited in an open, normal salinity environment between 30 m and 100 m in water depth.     

The mineralogy and origin of some Silurian bentonites, Welsh Borderland, U.K.

ABSTRACT Thirty clay-rich horizons from the Wenlock and Ludlow Series of the Welsh Borderland were analysed to investigate their mineralogy and possible origins. Two mineralogical assemblages were determined: an assemblage of illite-smectite and kaolinite of volcanic origin which was associated in many samples with an assemblage of illite and chlorite of detrital origin. Immobile chemical discriminants (Zr/TiO₂ versus Nb/Y) infer an originally rhyolitic ash composition with a possible temporal progression, from the Wenlock to Ludlow, to more differentiated compositions. The thin nature of the bentonites and lack of juxtaposed subduction related calc-alkaline magmatism suggests that the tuffs were derived from distant explosive eruptions from volcanic centres, possibly in NE Europe.