Mineralogy,textures, and whole-rock geochemistry of advanced argillic alteration: Hugo Dummett porphyry Cu–Au deposit,Oyu Tolgoi mineral district,Mongolia     

Bat-Erdene Khashgerel  Imants Kavalieris  Ken-ichiro Hayashi 《Mineralium Deposita》2008,43(8):913-932

Advanced argillic (AA) alteration is developed over a vertical interval of 500 m, above (and enclosing) Late Devonian quartz monzodiorite intrusions that accompany porphyry-style Cu–Au mineralization at the Hugo Dummett deposit. The AA alteration is mainly in basaltic rocks and locally extends into the overlying dacitic ash-flow tuff for about 100 m. The AA zone overprints porphyry-style quartz veins associated with quartz monzodiorite intrusions, but at least partly precedes high-grade porphyry-style bornite mineralization. Mineralogically, it consists of andalusite, corundum, residual quartz, titanium oxides, diaspore, alunite, aluminum phosphate-sulfate (APS) minerals, zunyite, pyrophyllite, topaz, kaolinite, and dickite, as well as anhydrite and gypsum, but is dominated by residual quartz and pyrophyllite. Alteration zonation is not apparent, except for an alunite-bearing zone that occurs approximately at the limit of strong quartz veining. Whole-rock geochemistry shows that the AA alteration removes most major elements except Si, Al, Ti, and P, and removes the trace elements Sc, Cs, and Rb. V, Zr, Hf, Nb, Ta, U, and Th are relatively immobile, whilst light REEs (La to Nd), Sr, Ba, and Ga can be enriched. Middle REEs (Sm to Gd) are moderately depleted; Y and heavy REEs (Tb to Lu) are strongly depleted except in two unusual samples where middle to heavy REEs are enriched.  相似文献   

Mongolian coal-bearing basins: Geological settings, coal characteristics, distribution, and resources     

Bat-Orshikh Erdenetsogt  Insung Lee  Delegiin Bat-Erdene  Luvsanchultem Jargal 《International Journal of Coal Geology》2009,80(2):87-104

This paper presents geological settings, stratigraphy, coal quality, petrography, reserves and the tectonic history of the Mongolian coal-bearing basins. This is based on a synthesis of the data from nearly 50 coal deposits. The results of ultimate and proximate analyses, and calorific value, maceral composition and vitrinite reflectance data is given.The coal deposits of Mongolia tend to become younger from west to east and can be subdivided into two provinces, twelve basins, and three areas. Main controlling factor of coal rank is the age of the coal bearing sequences. Western Mongolian coal-bearing province contains mostly high rank bituminous coal in strata from Late Carboniferous. The basins in southern Mongolia and the western part of central Mongolia have low rank bituminous coal in strata from the Permian. The northern and central Mongolian basins contain mainly Jurassic subbituminous coal, whereas the Eastern Mongolian province has Lower Cretaceous lignite. The Carboniferous, Permian and Jurassic coal-bearing sequences were mainly deposited in foreland basins by compressional tectonic event, whereas Cretaceous coal measures were deposited in rift valleys caused by extensional tectonic event. Petrographically, Mongolian coals are classified as humic type. Vitrinite/huminite groups of Carboniferous, Permian, and Cretaceous coal range from 44.9% to 82.9%. Inertinite group varies between 15.0% and 53.3%, but liptinite group does not exceed more than 7%. Jurassic coals are characterized by high percentages of vitrinite (87.3% to 96.6%) and liptinite groups (up to 11.7%). This might be explained by paleoclimatic conditions. Mongolian coal reserves have been estimated to be 10.2 billion tons, of which a predominant portion is lignite in the Eastern Mongolian province and coking coal in the South Gobi basin.  相似文献