大兴安岭南段白音查干锡多金属矿床锡成矿作用与银铅锌成矿作用关系研究：年代学、元素地球化学和同位素证据

In recent years, several large-scale Sn polymetallic deposits (e.g., the Baiyinchagan deposit) have been discovered in the southern Great Xing’ an Range, achieving a significant breakthrough of Sn ore-prospecting. These deposits occurred near some large-scale Ag-Pb-Zn deposits in the area which is dominated by Ag-Pb-Zn mineralization, showing a close relationship between Ag-Pb-Zn and Sn mineralization. However, until now, the relationship between these Ag-Pb-Zn and Sn mineralization has not been clearly recognized. Thus, in this study, we wish to choose the newly discovered Baiyinchagan Sn polymetallic deposit as a research subject to address this issue. Based on a systematic study on analyzing the geological features of the deposit, methods of U-Pb dating of cassiterite and 40Ar/39Ar dating of sericite are used, in an attempt to confirm the relationship of the spatial and temporal distribution regularities between Sn mineralization and Ag-Pb-Zn mineralization. Element geochemical, fluid intrusion and stable isotopic analyses of intrusions, wall rocks, and different stages of sulphide and gangue minerals will be carried out, in order to make clear the sources of ore-forming materials and the nature of ore-forming fluids, and constrain the relationship between Sn mineralization and Ag-Pb-Zn mineralization. Our research will enrich the mineralization theory of granite-related Sn deposit. At the same, the research production will also provide better understandings for regional Sn mineralization of the southern Great Xing’ an Range and help to instruct the further mineral prospecting.

近年来，大兴安岭南段相继发现了白音查干等大型锡多金属矿床，实现了锡矿找矿的重大突破。与以往不同的是，这些矿床产于以银铅锌矿化为主的地区，尤其是他们均发现于已探明的大型银铅锌矿床的外围及深部，显示出大规模银铅锌成矿作用与大规模锡成矿作用之间密切的联系。然而，到目前为止，对于两者之间关系的研究却十分薄弱。鉴于此，本申请拟选择新发现的白音查干大型锡多金属矿床为研究对象，在详细的矿床地质研究基础之上，尝试采用锡石原位U-Pb和绢云母40Ar/39Ar法厘定成矿时代，查明锡成矿作用和银铅锌成矿作用的时空分布规律；对有关侵入岩、围岩开展铅同位素研究，对不同矿化阶段的硫化物和脉石矿物开展元素地球化学、流体包裹体和稳定同位素研究，查明锡成矿作用和银铅锌成矿作用的成矿物质来源和成矿流体性质，进而揭示两种成矿作用之间的关系。本项目的实施不仅有利于丰富锡矿成矿理论，而且能够深化对大兴安岭南段锡成矿规律的认识。

近年来，大兴安岭南段相继发现了白音查干等大型锡多金属矿床，实现了锡矿找矿的重大突破。与以往不同的是，这些矿床产于以银铅锌矿化为主的地区，尤其是他们均发现于已探明的大型银铅锌矿床的外围及深部，显示出大规模银铅锌成矿作用与大规模锡成矿作用之间密切的联系。然而，到目前为止，对于两者之间关系的研究却十分薄弱。鉴于此，本项目选择新发现的白音查干大型锡多金属矿床为研究对象，开展系列研究工作，得出以下结论：（1）白音查干锡石年龄分布于在132.5至134.5Ma之间，代表了锡石的形成时代；（2）矿床成矿物质（Sn、Pb、Zn等）及流体可能主要来源于石英斑岩岩浆，锡与银铅锌成矿作用应属同一岩浆热液体系演化的产物；（3）白音查干矿床及大兴安岭南段中生代锡成矿作用和银铅锌成矿作用皆形成于伸展构造背景，受控于蒙古—鄂霍次克洋构造体系；（4）应注重锡林浩特—霍林郭勒矿集区内的Ag-Pb-Zn矿床（矿化）深部和外围的Sn矿找矿工作。本项目的实施不仅有利于丰富锡矿成矿理论，而且能够深化对大兴安岭南段锡成矿规律的认识，为大兴安岭地区下一步锡矿找矿勘查工作提供重要参考。