伊春-延寿成矿带壳幔相互作用与斑岩成矿

Continental geodynamics and regional metallogenesis are one of frontiers among geosciences. Crust-mantle interaction is a major way that material and energies exchange, migrate, and redistribute among different circles in the earth. It can control microscopically dominant species and types of ore deposits in the region. Yichun-Yanshou metallogenic belt, in which basic geology and metallogenic theories are relative weak, is located in the eastest part of central Asian orogenic belt. Granitic magmatisms and mineralizations are characterized by multistage and continuity since Phanerozoic. There are many predominant ore-forming geological conditions in it. Based on the given porphyry copper deposits, Using methods including typical deposits research, dating diagenetic and metallogenic ages, studying of fluid inclusions, and discriminating rock types of ore-bearing rock bodies in this project, We will study on spatio-temporal laws of granitic magmatism related to mineralization, survey the intrinsic relationship among different types of ore deposit from the view of regional metallogenesis, built the regional large-scale metallogenic models of material and energies exchangement among closing of the Paleo-Asian ocean, tectonic transferring of circum-Pacific ocean and crust-mantle interaction, and reveal crust-mantle interaction and geodynamics related to porphyry mineralization within orogenic environment since Phanerozoic in the Northeast China. The above researches maybe approve metallogenic theories and contents about porphyry copper deposits within orogenic belt.

大陆动力学和区域成矿学是当今地球科学研究的前沿领域，壳-幔相互作用是实现地球不同层圈之间物质与能量的交换、迁移与再分配的主要方式，宏观上可以控制一个区域的优势矿种和不同类型矿床的产出。伊春-延寿成矿带位于中亚造山带最东端，基础地质和成矿理论研究相对薄弱。区内显生宙以来花岗质岩浆活动与成矿具有多期性和连续性的特点，成矿地质条件优越。项目拟以近年发现的斑岩型矿床为主导，通过典型矿床地质研究、成岩-成矿年龄测定、流体包裹体特征研究及含矿岩体岩石类型判别等手段，研究与成矿相关的花岗质岩浆活动的时空规律，从区域成矿学的角度考察成矿带内各种类型矿床之间的内在联系，建立古亚洲洋闭合-环太平洋构造域转变-壳幔相互作用的物质能量交换-区域大规模的成矿模式，揭示东北地区显生宙以来碰撞造山带环境下壳-幔相互作用与斑岩成矿的地球动力学机制，丰富造山带斑岩型矿床的成矿理论和研究内容。

选取伊春-延寿成矿带内霍吉河、鹿鸣、翠宏山和五道岭四个典型矿床进行研究，明确鹿鸣和霍吉河矿床为典型的斑岩型矿床，翠宏山和五道岭为矽卡岩型矿床。矽卡岩矿床具有块状、细脉浸染状或角砾状矿石构造，硫同位素具有幔源分布特点（δ34S=1.2‰~5.78‰），成矿流体呈中温（240℃~ 280℃）、低盐度（2.89~11.6% NaCl eqv ）特征；斑岩型矿床具有细脉状、网脉状和细脉浸染状矿石类型，硫同位素显示主要来自地幔（δ34S =1.2‰~6.71‰），流体具有中高温（200℃~320℃）、低-中高盐度的变化（1.22~22.45% NaCl eqv）特点。流体温度及盐度的变化暗示热液主要来自岩浆并混有大气水。.与斑岩型Mo矿相关的花岗岩总体上呈近南北向带状展布。按Sr含量可分为三个阶段两种类型：（1）低Sr类花岗岩：主要形成于早侏罗世，侵位于201.1±3.9Ma~ 194.8±0.7Ma和182.3±1.2Ma~184.0±1.5 Ma两个时期，岩石Sr含量普遍低于250ppm，主要为黑云母花岗岩、二云母花岗岩、花岗斑岩和正长花岗岩，以富集轻稀土和明显的Eu负异常为特征，属于高钾钙碱性-弱碱性、准铝-过铝质花岗岩，四个典型矿床均有分布，构成矿体的赋矿围岩。（2）高Sr类花岗岩：形成于174.0±2Ma ~176.2 ±2.1Ma的中侏罗世，Sr含量普遍高于400ppm，岩性主要为花岗闪长岩和似斑状花岗闪长岩，以轻稀土富集、Eu无负异常或弱负异常，高Sr、低Y且富Na为特点，属于高钾钙碱性、准铝质-过铝质花岗岩，具有典型埃达克岩的地球化学属性。该类型花岗岩仅在霍吉河与鹿鸣矿区出露，霍吉河矿床见有细脉状黄铜矿分布其中。.结合近年来发表的相关成果，伊春-延寿成矿带中与多金属矽卡岩型矿床有关的是早侏罗世A型及I型花岗岩，与斑岩型Mo矿床相关的为中侏罗世埃达克岩。埃达克岩不仅是斑岩型矿床的找矿标志，更重要的是它代表着板块消减或陆陆碰撞的大构造事件，暗示花岗岩的形成与太平洋板块的俯冲有密切相关。这种壳幔相互作用的岩浆形成机制，对伊春-延寿成矿带乃至中国东部大陆动力学研究及成矿均具有重要的启示及指导意义。