| The Duobuza copper deposit is located in Ali Region Gaize county and Wumatownship of Tibet, is discovered by Tibet Provincial Bureau of geological prospectinggeological five teams in super large ore deposits with prospects. The deposit is locatedin the Qiangtang-Sanjiang composite plate of Duobuza tectonomagmatic belt,Metallogenic belt belong to the Western Section of Bangonghu-Nujiang MetallogenicBelt.In this paper, the geological background of the deposit characteristics, orestructure, chemical composition, fluid inclusions geochemical characteristics werestudied. The system summarizes the Duobuza copper deposit, geological characteristicsand the nature of the fluid inclusions. Studies have shown that：1) The Duobuza copper deposit of Tibet is located in the Qiangtang Sanjiangcomposite plate of Duobuza tectonomagmatic belt, metallogenic belt belong to theBangonghu-Nujiang Metallogenic Belt, is a typical porphyry copper deposit. Theorebody produced in the granodiorite porphyry body and the contact zone, LowerJurassic Quse group as the main host strata, Ore body toward the southwest, inclined tothe south. the Duobuza copper deposit formed in the tectonic setting is the activecontinental margin.2)Structure of ores is disseminated-veinlet-disseminated structures, vein-finevein structure, blocky structure, as the brecciated structure, honeycomb structure, soilstructure, crumb structure, gelatinous structure. Ore structure mainly for the crystallinestructure, metasomatic texture, as exsolution structure and crushed between the grainstructure. Ore minerals are mainly chalcopyrite, pyrite, magnetite, for molybdenite,malachite, azurite, bornite, copper etc.The Duobuza copper deposit, alteration ofcountry rock alteration type of special development, mainly for potassium, silk ofBritish rock, silicification, pyritization, as clay, green plate lithification etc. Root Zelkowa acuminata deposit mineral assemblages, the mineralization is divided into thelate magma, hydrothermal period, supergene stage, where in the hydrothermal period isdivided into magnetite-molybdenite stage, chalcopyrite-pyrite stage, The anhydrite-pyrite stage.3) Various types of ore are mainly developed with mineral inclusions, time forfluid inclusions and gas inclusions, pure gas inclusions, the pure liquid inclusions arerelatively few. Homogenization temperature mainly concentrated in350400℃,indicating that the deposit belongs to the medium and high temperature hydrothermaldeposit; Different mineralization stages homogenization temperature change range issignificantly different, from magnetite-molybdenite chalcopyrite and pyrite phase tophase to hard gypsum and pyrite stage, the average temperature decreased significantly,from379.4℃to333.6℃and322.9℃. Metallogenic pressure between35x105Pa70x105Pa, the deposit was formed in a high pressure environment. Frommagnetite-molybdenite chalcopyrite and pyrite stage to stage pressure decreasedsignificantly, from114.5x105Pa to47.9x105Pa, whereas in hard gypsum and pyritestage pressure also increased to74.8x105Pa.Ore forming fluid salinity mainlyconcentrated in the340wt%NaCl.eqv, belong to high salinity fluid；The salinity ofthe fluid of different mineralization stages are not the same, the magnetite-molybdenite phase average salinity of42.8wt%NaCl eq, pyrite chalcopyrite-phaseaverage salinity of36.6wt%NaCl eq, hard gypsum and pyrite stage average salinity of39.3wt%NaCl eq. Density changes in the1.0761.095g/cm3. Magnetite-molybdenitestage average fluid density is1.076g/m3, pyrite chalcopyrite-phase average fluiddensity is1.087g/m3, whereas in hard gypsum and pyrite stage average fluid density is1.080g/m3.4)Inclusion gas is the main component of CO2, H2O and CH4, component isrelatively simple, represent an oxidizing environment. Liquid phase compositionmainly contains the Cl-, SO42-, Na+, Ca2+, K+, F+, and the Na+and Cl-ionsconcentration is high, that contains a large number of inclusions in halite daughtercrystal. Ore forming fluid is rich in Na, K, Cu, Ca and other elements. Quartz δ18Ovalue of6.8per thousand to10.3per thousand, average of8.15per thousand. Theδ18OH2Ovalue of0.47per thousand to3.92per thousand, average of2.29per thousand.δDH2Ovalue of-97.9per thousand to-76.4per thousand, average of-87.9per thousand.Characteristics of hydrogen and oxygen isotopes suggest, ore-forming fluid comesmainly from magmatic water.5) Through domestic and international famous porphyry copper contrast, foundDuobuza copper and they have similar geological features and fluid properties, suggesting the Duobuza copper also have the potential to form superlarge porphyrycopper deposit in. |
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