The Study On Metallogenism And Magmatism Of The Darbut Tectono-magmatic Belt,Western Junggar

The magmatism of the Darbut tectono-magmatic belt during Late Paleozoic period in Xinjiang is characterized by multiple period, variable type and diverse petrogenesis, and metallogenic conditions are favorable. There are many deposits such as Hatu large gold deposit, Baogutu Cu-Au deposits, Bieluagaxi Au deposit and newly discovered deposits such as Hongyuan Cu-Mo deposit and Tuketuke Cu deposit. However, for already existing as well as newly discovered deposits(ore occurrences), the study on its magmatic metallogenic specialization and the sources of minerals is extremely weak, and it is not yet available to be well explained for the deposits which have been found already, or guidance prospecting using existing data at present, and can not be compared with the other ore-bearing porphyries in the same tectono-magmatic belt like Baogutu neither, Which largely restricted the development of the prospecting of Au, Cu, Mo in the south of Western Junggar. Therefore, whether the studies on the Au-Cu-Mo deposits(ore occurrences) which have been found already, or on the small acidic intrusions which did not show significant mineralizations, are the new entry point of mineralization connection and comparation This dissertation is object on the small acidic intrusions of the Darbut tectono-magmatic belt in the south of Western Junggar. Through the study of its petrology, petrography, geochronology and geochemistry, to explore the metallogenic specialization of Au-Cu-Mo, and gained some achievement as follows:1.The lithologies of large batholiths such as Miaoergou, Akebasitao and Tiechanggou are mainly consists of syenogranite and adamellite, its diagenetic ages are subject to 308~296 Ma, and the majority of them are alkaline series of A2 type granites, and formed in the short-lived late orogenic stage of extensional structure system during Late Carboniferous-Early Permian. They probably have the potential to provide heat sources for secondary migration and enrichment of Cu, Au, but there are no large mineralization potential for themselves.2.The lithologies of small acidic intrusions such as Baogutu and Bieluagaxi are mainly consists of quartz diorite, diorite, granodiorite and granite-porphyry, its diagenetic ages are subject to 310~320 Ma, and the majority of them are calc-alkaline series of I type granites. Strong crust-mantle magma mixing activities have been occurred during the emplacement among a few small intrusions, and individual intrusions have adakitic geochemical characteristics, and show good Cu-Au mineralizations, and formed in the subduction-related island arc system which is extremely favorable for mineralization.3.The magma mixing granite(Buerkesitai and Tasikuola granite compared with Xiaerpu granite), adakite(Dulunhe granite compared with Baogutu granite) and some alkaline series large batholiths(Akebasitao granite compared with Hongshan granite) have an excellent contrast in petrology, geochronology, geochemical characteristics and ore potential, we suppose that the initial Au-Cu-Mo metallogenic belt should be near to the E-W in advance(NW fault zone such as Darbut fault reform or even destroy the original ore body during a late stage), rather than predecessors thought close to NE-SW or be controlled by NW fault zone such as Darbut fault, and suffered NE-SW fault structure sinistral strike-slip shearing at a later stage, resulting in the present distribution pattern. It also shows that Darbut fault was formed after the emplacement of Akebasitao and Hongshan granite(~305 Ma), that is the time to fault initiation no earlier than late Late Carboniferous.4.The main mineralization of the study region have metallogenic regularities of “Three Belts, Three Categories and Three Periods”: magmatic hydrothermal type gold deposit in the north(~318 Ma); porphyry type molybdenum deposit in the middle zone(~296 Ma); adakite and magma mixing-related copper-gold deposit in the south(~313 Ma).Based on the above understandings, we can draw a conclusion that Dulunhe granite and can be compared with Baogutu granite(adakite), Buerkesitai and Tasikuola granite can be compared with Xiaerpu granite(Tuketuke Cu-Mo; magma mixing), and Bieluagaxi Au metallogenic belt may extend to Saertuohai or even farther eastern, are respectively favourale sections for prospecting new ore deposits such as adakite, magma mixing-related Cu-Au deposits, and structure altered rock type and quartz vein type Au deposits, as well the prospecting target areas of this study.