Petrochemical characteristics of carbonaceous shales in the eastern Bureya massif and their precious-metal mineralization

2013 ◽  
Vol 54 (6) ◽  
pp. 627-636 ◽  
Author(s):  
A.I. Khanchuk ◽  
V.G. Nevstruev ◽  
N.V. Berdnikov ◽  
Nechaev
1990 ◽  
Vol 54 (376) ◽  
pp. 485-493 ◽  
Author(s):  
C. J. Stanley ◽  
A. J. Criddle ◽  
D. Lloyd

AbstractPrecious and base metal selenide minerals have been identified in gold-bearing carbonate veins cutting Middle Devonian limestones of the Torquay Limestone Group at Hope's Nose, Torquay. The selenide assemblage consists of clausthalite (PbSe), tiemannite (HgSe), klockmannite (CuSe), umangite (Cu3Se2), tyrrellite (Cu,Co,Ni)3Se4, trustedtite (Ni3Se4), penroseite (NiSe2), naumannite (Ag2Se), eucairite (AgCuSe) and fischesserite (Ag3AuSe2), only clausthalite having previously been reported from Britain. They are associated with palladian gold, gold, hematite, and accessory pyrite and chalcopyrite in a gangue consisting predominantly of calcite; alteration products include cerussite, malachite, aragonite and goethite.The relative abundance of Au, Ag, Hg and Se is a characteristic feature in the uppermost parts of some precious metal ‘epithermal’ systems. The occurrence at Hope's Nose is related to both structural and lithological factors: a deep-seated NW-SE structural lineament, the Lundy-Sticklepath-Lustleigh-Torquay fault; local thrusting, and to an association of basic-intermediate igneous rocks with a sedimentary sequence including carbonaceous shales and limestones. The mineralization is considered to be post-Variscan, probably Permo-Triassic in age.


Author(s):  
Autumn Flynn ◽  
Kelly McDaniel ◽  
Meredith Hughes ◽  
David Vogt ◽  
Nathan Jui

A photocatalytic system for the dearomative hydroarylation of benzene derivatives has been developed. Using a combination of an organic photoredox catalyst and an amine reductant, this process operates through a reductive radical-polar crossover mechanism where aryl halide reduction triggers a regioselective cyclization event, giving rise to a range of complex spirocyclic cyclohexadienes. This light-driven protocol functions at room temperature in a green solvent system (aq. MeCN), without the need for precious metal-based catalysts or reagents, or the generation of stoichiometric metal byproducts.


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