Study On The Geological Characteristics And The Origin Of Metallogenic Elements From Nuri Cu-W-Mo Deposit In Tibet

Nuri Cu-W-Mo deposit ilocated in the Yanshan Himalaya tectonic stage of continental margin magmatic arc in the eastern part of the Yarlung Zangbo River suture zone, the northern margin of the Gangdise metallogenic belt, is a typical skarn deposit.The ore bodies are controlled by anticline area control.which exists in the anticline and syncline overlapping sections of the K1b4 interlayer fracture and fractured zone of skarn.. A total of 12 orebody delineation, is mainly stratoid, lenticular and vein. The main ore minerals are chalcopyrite, molybdenite, scheelite, mainly in fine-grained euhedral hypidiomorphic texture, disseminated, speckled, massive structure. The gangue minerals include garnet, epidote, quartz, carbonate rocks and a very small amount of calcite.High field strength elements(HFSE) of Trace elements in Molybdenite which enrich the LREE is loss. The ratio that Y/Ho, Zr / Hf, Nb/Ta has a certain difference in range in Molybdenite. It Indicates that the main metallogenic stage ore-forming fluid mixed with different level external fluid. The overall features are still given priority to with early chemical and physical properties of ore-forming fluid. The distribution patterns of the fluid whic Rich molybdenum try to right, the anomaly of Eu and Ce is negative. The anomaly of loss Eu may be associated with the skarnized magma crystallization separation microtek in caused a lot of plagioclase, the original fluid loss in Eu strongly;Negative Ce anomaly might be due to the initial fluid for oxidation environment, Ce3+by oxidation of Ce4+ with rare earth separation system.Scheelite ore trace elements characterized by loss of high field strength elements(HFSE), LREE enrichment.the ratio range of Hf/Sm、Th/La、Nb/La is far less than 1, the ratio range and extent of Y/Ho、Zr/Hf、 Nb/Ta have some differences. It Suggest that Nuri deposits overall is given priority to with rich Cl hydrothermal ore-forming fluid. In the main metallogenic period with the external fluid, different level overall features are still given priority to with early chemical and physical properties of ore-forming fluid. ΣREE is not high, LREE is relatively HREE more enrichment; showing the right distribution mode again, the element structure is single, particular value changed small, indicated that the scheelite REE is highly homologous. δE negative anomaly is weak which particular value of theδE range of 0.768~0.910, with a mean of 0.825, the variation range is narrow; TheδCe range of 1.066~1.066, with a mean of 1.087, basically did not see the Ce or very weak positive Ce anomaly, largely represents the reductive environment characteristics of ore-forming fluid.The value of δ18 OH2 O in Fluid inclusions of Garnet and quartz range from2.96 to 7.14 ‰.Magmatic is the subject of the ore-forming hydrothermal, at the same time receive a large amount of rain in the hydrothermal migration, ore-forming hydrothermal made initial primary magma water gradually transition to the native a mixture of magmatic water and rain.The value of the δ34S ranged very small, and mostly positive, occasional negative, distribution is typical of the tower, and positive deviation. Shows that the S-isotope have a high degree in homogenization, occurrence in the ore-forming fluid of sulfide in the process of crystallization precipitation is not which aroused the fierce attacks from the S-isotope fractionation, suggested that the source of the sulfur is relatively single.The characteristic value of isotope of Pb are less than 9.58, between the crust and mantle, and indicates that metallogenic material of Nuri deposit mainly comes from mantle source, may be mixed with some shell source material in the process of migration.Combined with comprehensive analysis found that Re isotope, Mo in copper molybdenum tungsten deposit metallogenic substances may comes from a single deep mantle source. The scheelite is likely to come from deep crust source magma crystallization differentiation after rich tungsten fluid along the process of tectonic fissures and surrounding rock strata contact metasomatic reaction than horse group, eventually leading to Ca2 + and WO3-4 combine to form the scheelite. Mainly for the initial primary magma and hydrothermal ore-forming water gradually transition to the native magmatic water and mixed fluid of tianshui. Structure is relatively single, S isotope shows that S the main source of magma. Pb isotopes show that Pb deposit for excluding radiogenic lead normal, for mixed source.