The Temporal And Spatial Evolution Of The Mesozoic Granites And Its Relations To The Metallogenesis In Western Zhenjiang Province

In 2009, Qinzhou-Hangzhou metallogenic belt was listed as one of the most important prospecting belts in China. As the eastern part of this metallogenic belt, Western Zhejiang Province is well-known for its complicated geological background and conditions favoring formation of polymetal deposits. Based on the project known as "The Metallogenic Conditions and Regularity of Cu-Au Polymetal Deposits in the Middle-Western Segment of the Jiang-Shao Collision Orogenic Belt", a three-year fieldwork associated with this project, as well as a better understanding of the regional geological settings and its history of development, this paper took advantage of several lines of evidence, like petrological, element geochemical (major, trace and rare-earth elements), isotope geochemical (e.g. Rb-Sr, Sm-Nd, S, O-H isotopes), zircon SHRIMP U-Pb dating, fluid inclusion and so on, in order to constrain the temporal and spatial evolution of the ore-related granites, the petrological characteristics and the origins of the granites, the relationships between the magmatism and the mineralization (namely the geological background and conditions of endogenetic polymetal deposits in this area), and the spatiotemporal feature or interrelation among regional structure, magmatic process, hydrothermal solution, and metallogenesis. My findings should be significant in theory and practice for further geological prospecting in this area, major achievements of this paper are as follows:I believe that "regional structure controlling diagenesis, while granitic rocks controlling ore- deposits" seems a universal regularity in western Zhejiang province. Based on a systematic progress in the chronology of magmatic rocks in this area and many other data of ages dating by inheritable magmatic zircons, I have rebuilt the evolutive history of regional structure in western Zhejiang, this makes the further understanding of regionally metallogenic processes from a new perspective possi- ble.The Tongcun porphyry Mo-(Cu) deposit, Lishanling porphyry Cu deposit in Changshan County, Yanqian magmatic hydrothermal type W-Sn-(fluorite) deposit in Changshan County, Yinkeng porphyry Mo deposit in Jinhua City and so on were systematically analyzed as classic deposits. Particularly, the ages of diagenesis and metallogenesis of Lanhuawu granites in Changshan County, Linghou granites in Jiande City, Ruhong (Tongshan) granites in Chun’an County, Zhiling- tou granites in Suichang County as well as the polymetal deposits associated with these granites were father precisely determined, which makes it possible that most endogenetic ore deposits presenting in this region can be in essence studied according to metallogenic space, time and material sourceThe ages of granites associated with Mesozoic metallogensis in the studied area was dated by zircon SHRIMP U-Pb method, and the Yanshanion magmatic activities in this region was firstly divided into three stages, whose time ranges are 172～158Ma,144～ 127Ma, and 114～108Ma, respectively. The petrological and/or geochemical characteristics, source and tectonic settings of these magmatic activities, as well as their relationships to regional metallogenesis at each stage was systematically summarized. A framework of the Mesozoic diagenesis-metallogenesis and its characteristics of spatiotemporal distribution in this region was thus proposed, particularly, this work would provide a reliable evidence of chronology for the understanding of the evolutive history and dynamic mechanism of regional tectonic-magmatic activitiesBased on the studies (doing research of regionally classic deposits and summary of regional ore- controlling factors and metallogenic regularity) above and in terms of the essentials of metallogenic system theory, I found that the Mesozoic metallogenetic system in Western Zhenjian Province can be demonstrably classified into two systems, four subsystems, and six metallogenetic series. Metallogenetic models and prospecting models at the three stages were further established for first-choice mineral resources and types in future prospecting.I suggest for that there is a gradually younger trend of the Mesozoic magmatic activities from northeastern Jiangxi Province, to western Zhejiang Province, to the middle and lower reaches of Changjiang River, and to east of Jiang-Shao fault zone, it is the different deep-seated tectonic background, and the different participating extent of mantle material during diagentic process that result in the different characteristic of regional diagenesis and metallogenesis in these areas.