地学前缘 ›› 2020, Vol. 27 ›› Issue (2): 165-181.DOI: 10.13745/j.esf.sf.2020.3.17

• 特色地域成矿背景与成矿作用 • 上一篇    下一篇

皖赣沿江地区中生代壳幔相互作用与多成因夕卡岩成矿过程研究综述

杜杨松1(), 曹毅1, 秦新龙2, 庞振山3, 杜轶伦3, 王功文1   

  1. 1.中国地质大学(北京) 地球科学与资源学院, 北京 100083
    2.江苏省有色金属华东地质勘查局, 江苏 南京 210007
    3.中国地质调查局 发展研究中心, 北京 100037
  • 收稿日期:2019-12-01 修回日期:2020-01-05 出版日期:2020-03-25 发布日期:2020-03-25
  • 作者简介:杜杨松(1957-),男,教授,主要从事岩石学和矿床学研究。E-mail: duys5510@cugb.edu.cn
  • 基金资助:
    国家自然科学基金项目(41730426);国家自然科学基金项目(41030423);中国地质调查局地质调查项目“整装勘查区矿产地质调查与找矿预测”(WKZB1911BJM300369/003)

A review on the Mesozoic crust-mantle interaction and metallogeny of various skarn deposits in the Jiangxi-Anhui segment along the Yangtze River

DU Yangsong1(), CAO Yi1, QIN Xinlong2, PANG Zhenshan3, DU Yilun3, WANG Gongwen1   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
    2. East China Mineral Exploration and Development Bureau for Non-Ferrous Metals, Nanjing 210007, China
    3. Development and Research Center, China Geological Survey, Beijing 100037, China
  • Received:2019-12-01 Revised:2020-01-05 Online:2020-03-25 Published:2020-03-25

摘要:

在皖赣沿江地区分布着大量中生代侵入岩体及其岩石包体和相关的夕卡岩矿床。本文在综合整理作者研究团队近30年来所获得的区内大部分侵入岩体及其岩石包体和夕卡岩矿床研究资料的基础上,聚焦区域中生代壳幔相互作用与多成因夕卡岩成矿过程分析,为发展壳幔成矿学打下一定基础。基性侵入岩和镁铁质岩石包体的同位素年代学和岩石地球化学资料表明,皖赣沿江地区在中生代发生了碰撞后(145~135 Ma)富铜金和造山后(130~120 Ma)富铁金幔源岩浆底侵作用和相应的壳幔混源岩浆作用。壳幔混源岩浆作用主要包括结晶分异作用、同化混染作用、岩浆混合作用和岩浆熔离作用。夕卡岩矿床地质调研和镜下观察结果显示,两期壳幔混源岩浆侵入晚古生代到早中生代围岩地层后引发了多成因夕卡岩成矿作用,形成了接触交代、层控、岩浆和复合叠加等多成因夕卡岩矿床。接触交代、层控、岩浆和复合叠加夕卡岩矿床分别以热液交代、沉积+热液交代、岩浆结晶+热液交代和沉积+岩浆结晶+热液交代矿物组合和结构构造为特征。在碰撞后酸性-中酸性侵入岩体中产有富Cu和Zn等成矿物质的元古宙变质岩包体,表明碰撞后富铜金的底侵玄武岩浆或其演化岩浆在浅位岩浆房中同化了元古宙变质基底成矿物质(铜锌等)储库导致铜进一步富集,从而形成更富铜的酸性-中酸性岩浆。在碰撞后中基性-基性侵入岩体中产有含大量Cu-Fe硫化物(黄铜矿和磁黄铁矿)和氧化物包裹体的深位和浅位堆积岩,表明碰撞后富铜金的底侵玄武岩浆在深位岩浆房中和其演化岩浆在浅位岩浆房中发生了强烈的结晶分异作用导致铜铁亏损,形成更富金的中基性-基性岩浆。酸性-中酸性侵入岩体中夕卡岩包体和夕卡岩中辉长岩-夕卡岩过渡包体的存在表明,碰撞后富铜金的底侵玄武岩浆在侵位处同化晚古生代含铜铁矿源层的碳酸盐地层导致铜进一步富集,形成更富铜的夕卡岩岩浆。更富铜的酸性-中酸性岩浆、更富金的中基性-基性岩浆和更富铜的夕卡岩岩浆是形成碰撞后时期接触交代和层控夕卡岩铜矿、接触交代夕卡岩金矿和岩浆夕卡岩铜矿的最重要控制因素。在造山后中基性-基性侵入岩体中产有含大量Cu-Fe硫化物(黄铜矿和磁黄铁矿)和氧化物包裹体的堆积岩,表明造山后富铁金的底侵玄武岩浆在深位岩浆房中发生了强烈的结晶分异作用导致铜铁亏损,从而形成更富金的中基性-基性岩浆。造山后富铁金的底侵玄武岩浆在侵位处同化晚古生代含铜铁矿源层的碳酸盐地层、早中生代铁矿源层或者早中生代铁硅矿源层,导致铁、铁和铁硅的进一步富集,分别形成更富铁的夕卡岩岩浆、基性岩浆和中基性岩浆。更富金的中基性-基性岩浆及更富铁的夕卡岩岩浆、基性岩浆和中基性岩浆是形成造山后时期接触交代夕卡岩金矿、岩浆夕卡岩铁矿、矿浆型铁矿和接触交代夕卡岩铁矿的关键控制因素。

关键词: 壳幔相互作用, 夕卡岩矿床, 成矿过程, 中生代, 皖赣沿江地区

Abstract:

A large number of Mesozoic intrusions, their enclaves and related skarn ore deposits are distributed along the Yangtze River.We present thirty years of our study on Mesozoic intrusions with xenoliths and associated skarn deposits in the Jiangxi-Anhui segment along the Yangtze River. Specifically, this paper focuses on the analysis of the Mesozoic crust-mantle interaction and metallogeny of various skarn deposits in the area in order to lay some foundation for the development of crust-mantle metallogeny. Isotopic chronological and petro-geochemical data of the basic intrusive rocks and mafic xenoliths confirm the occurrence of underplating of the post-collisional mantal-derived magma (145-135 Ma) rich in Cu and Au, and the post-orogenic mantal-derived magma (130-120 Ma) rich in Fe and Au. In addition, the existence of similar activities of magma from the mantle with crust in the Mesozoic can be confirmed from the data. The activities of magma from the mantle with crust mainly include crystalline fractionation, assimilation and contamination, magma mixing, and magma liquation. Geological investigation and microscopic observation of skarn deposits show that the two episodes of intrusions of various mantle-derived magmas with crust into Late Paleozoic to Early Mesozoic wallrock strata led to mineralization of various skarns responsible for the formation of various skarn deposits, including contact replacement, stratabound, magma, and compound and superimposed skarn deposits. These deposits are characterized by distinct types of mineral assemblage and texture as well as the structure of hydrothermal replacement, sedimentation-hydrothermal replacement, magma crystallization-hydrothermal replacement, and sedimentation-magma crystallization-hydrothermal replacement, respectively. The existence of the xenoliths of Proterozoic metamorphic rocks, rich in ore-forming materials such as Cu and Zn in the post-collisional acidic to intermediate-acidic intrusions, supports contamination of the Proterozoic metamorphic basement in the shallow-level magma chamber by the post-collisional underplating basaltic magma rich in Cu and Au or its evolved magma. The contamination resulted in Cu further enrichment to form acidic to intermediate-acidic magmas with increased Cu. The occurrence of the cumulates containing a lot of Cu-Fe sulfides (chalcopyrite and pyrrhotite) and oxide inclusions in the post-collisional intermediate-basic to basic intrusions, is consistent with intensive crystalline fractionation of the post-collisional underplating basaltic magma rich in Cu and Au and its evolved magma in the deep-level and shallow-level magma chambers, respectively. The crystalline fractionation caused depletion in Cu and Fe to form intermediate-basic to basic magmas with even higher Au enrichment. Text Some skarn enclaves occur in the post-collisional acidic to intermediate-acidic intrusions, and few enclaves of the transition of gabbro to skarn exist in the skarn. This fact indicates the contamination of the Late Paleozoic carbonate strata with Cu and Fe source bed by the post-collisional underplating basaltic magma rich in Cu and Au in the intrusive location, leading to Cu further enrichment to form a skarn magma with increased Cu. The acidic to intermediate-acidic magmas with increased Cu, the intermediate-basic to basic magmas with increased Au, and the skarn magma with increased Cu are the most important controlling factors for the formations of contact replacement and stratabound skarn Cu, contact replacement skarn Au, and magmatic skarn Cu ore deposits during the post-collisional period, respectively. The occurrences of the deep-level and shallow-level cumulates containing a lot of Cu-Fe sulfides (chalcopyrite and pyrrhotite) and oxide inclusions in the post-orogenic intermediate-basic to basic intrusions provide evidence for intensive crystalline fractionation of the post-orogenic underplating basaltic magma rich in Fe and Au in the deep-level magma chamber. The crystalline fractionation combined with magma mixing caused depletion in Cu and Fe to form intermediate to basic magmas with higher Au enrichment. Contaminations of the Late Paleozoic carbonate strata with Cu and Fe source bed, the Early Mesozoic Fe source bed, and the Early Mesozoic Fe and Si source bed by the post-orogenic underplating basaltic magma rich in Fe and Au in the intrusive location led to Fe, Fe, and Fe and Si further enrichments to form skarn, basic, and intermediate to basic magmas more enriched in Fe, respectively. The intermediate-basic to basic magmas with increased Au enrichment as well as the skarn, basic, and intemediate-basic to basic magmas with increased Fe enrichment are predominantly responsible for the formation of contact replacement skarn Au, magmatic skarn Fe, ore magma Fe, and contact replacement skarn Fe ore deposits during the post-orogenic period, respectively.

Key words: crust-mantle interaction, skarn ore deposit, mineralization process, Mesozoic, Anhui-Jiangxi segment along the Yangtze River

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