Research On The Relationship Of Alteration Characteristics And Mineralization Of Layikeleke Porphyry Deposit From East Junggar, Xinjiang

Layikeleke porphyry deposit is located at the south-central segrnment of Qiongheba district, the district is one of the most important Cu-Au metallogenic belt. On the basis of petrology, mineralogy, mineral deposit geology, geochemisty, zircon U-Pb geochronology and Re-Os ages of molybdenite, this study makes investigation on geological characteristics of the deposit. And the geological features, the alteration and mineralization of Layikeleke Porphyry Deposit were systematically researched.The feature of alteration type, alteration zoning and mineral assemblages were confirmed.At the same time, age and genesis of rock, metallogenic material source and genesis of the deposit also were considered. Based on theses evidences, we extracted the prospecting information, and established the prospecting model.The geochemical of tonalite in Layikeleke mine show that rocks are peraluminous low potassium calc-alkaline. The primitive mantle normalized trace element patterns are characterized by the enrichment of the LILE (K、Rb、 Ba、Sr) and depletion of the HFSE (Nb,Ta, P, Ti). High Ba, Sr, high La^/YbN, Sr/Y ratios, distinct Nb, Ta and Ti depletion, and are comprehensively called high Ba-Sr granitoids. The testing results of Hf isotope, shows that Layikeleke tonalite has high and positive εHf(t) (+10.88～+15.83) and younger model age(439.10Ma～711.66Ma). These geochemical and Hf isotope characteristics indicate that they were related to partial melting of subducted oceanic crust. In this paper, U-Pb dating of SHRIMP zircon of the rock is 418Ma-419Ma, Re-Os ages of molybdenite is 409Ma-411Ma, suggesting that, Layikeleke porphyry deposit was derived from late Silurian-early Devonian magmatic and hydrothermal activity.Layikeleke porphyry deposit developed alteration. Late hydrothermal alteration to the original rocks in turn can be divided into five stages. The first stage is potassic alteration; the main type is the metasomatism of secondary biotite to amphibole. The second stage is sericitization alteration; the main type is the metasomatism of microcrystalline sericite to plagioclase. Then is phyllic alteration, the main type is the replacement of the secondary quartz and phyllic to the combination of plagioclase-biotite-quartz in original rocks. The fourth stage is silicification, the mian type is different size and inregularly shaped quartz veinlets distributed along the rock fissures or cut through the altered rocks. The last stage is laumontitization and carbonatitization, superimposed on the above alteration. Alteration mainly controlled by the occurrence of rocks and the structure. The center is tonalite, from the inside out followed developed pyrite phyllic zone, sericitization zone, muddy zone, propylitization zone. Pyrite phyllic zone is the innermost zone of the deposit, mianly developed phyllic, sericitization, pyritization, silicification, etc., which is closely related to the mineralization. Sericitization zone mainly developed sericitization, silicification, etc.. Muddy zone obviously controlled by fault structer in mine and developed clayzation, silicification, etc. Propylitization zone mainly developed in the contact zone of tonalite and the wall rocks. The alteration includes epidotization, chloritization, and carbonate and so on, which is weak alteration and mineralization.Mineralization is close to alteration in Layikeleke porphyry deposit and mainly developed in altered rocks, which show no mineralization in unaltered tonalite. With the evolution of alteration, copper-molybdenum mineralization starts to appear. In early potassium stage, only magnetite output, with the development of sericitization, pyrite and chalcopyrite begin to appear. Phyllic alteration stage is the most important enrichment period of pyrite and chalcopyrite, and molybdenite appears in this stage. Then in silicification stage, also developed chalcopyrite and molybdenite, superimposed on pre-alteration, enriched on mineralization. The lead and zinc mineralization in the west mine is the result of late hydrothermal alteration.Extracted ore prospecting information of geologic, geophysical, geochemical, we established the following prospecting model:(1) lower Devonian Tuoranggekuduke Formation neutral and acidic volcano clastic rock;(2)tonalite;(3) the combination of abnormal-high polarization, low resistance, low magnetic anomaly andlow gravity;(4) Zn、As、Au、Co、Cr、 Cu、Mn、Mo、Nielements geochemical anomaly distribution area.