中亚成矿域斑岩大规模成矿特征:大地构造背景、流体作用与成矿深部动力学机制
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1.中国科学院地质与地球物理研究所;2.中国地质大学(北京)地球科学与资源学院;3.吉林大学地球科学学院;4.北京大学地球与空间科学学院;5.南京大学地球科学与工程学院

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本文为国家自然科学基金项目(编号41390440、41390445和41025008)资助的成果。


Large- scale porphyry- type mineralization in the Central Asian metallogenic domain: tectonic background, fluid feature and metallogenic deep dynamic mechanism
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1.Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing;2.Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing;3.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences (Beijing);4.College of Earth Sciences,Jilin University;5.School of Earth and Space Sciences,Peking University;6.Institute of Geology and Geophysics,Chinese Academy of Sciences;7.School of Earth Sciences and Engineering,Nanjing University

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    摘要:

    中亚成矿域夹持于西伯利亚、东欧和塔里木- 华北克拉通之间,展布范围与全球显生宙大陆地壳生长最典型的增生型造山带——中亚造山带相当,并产出一系列大型—超大型斑岩铜(-金)、斑岩钼及斑岩铜(-钼)矿床。斑岩成矿作用自西向东存在明显差异,可高度概括为具‘西铜东钼、早铜晚钼’特征。基于前寒武纪基底性质、成矿大地构造背景以及斑岩成矿特征方面的系统综合研究,以重要构造线为界,将成矿域进一步划分为三个成矿省:哈萨克斯坦斑岩Cu(- Au- Mo)、蒙古斑岩Cu(- Au)和中国东北斑岩Mo(- Cu)成矿省。哈萨克斯坦成矿省具新太古—古元古代结晶基底;四个大型斑岩Cu矿床形成于早古生代增生造山过程(481~440Ma),而绝大多数矿床为晚石炭世(330~295Ma)集中爆发成矿的产物。古亚洲洋西段,沿我国中天山—伊犁南缘—吉尔吉斯北天山—中哈萨克斯坦—科克切塔夫至成吉思线性展布的古生代岩浆弧与哈萨克斯坦山弯构造共同制约了斑岩成矿作用;增生造山向山弯构造的转换阶段为斑岩集中成矿期。蒙古斑岩成矿省亦具新太古代—早古元古代结晶基底;斑岩成矿作用主要发生在泥盆纪 (~370Ma)和三叠纪(~240Ma)两个时期,为图瓦- 蒙古山弯构造演化过程中两个局部时段的突发成矿;早期成矿事件与古亚洲洋体系向南戈壁微地块下的俯冲增生造山有关,晚期成矿可能是蒙古—鄂霍茨克洋俯冲作用的结果。中国东北斑岩成矿省广泛发育新元古代结晶基底和泛非事件岩石学记录;奥陶纪(482~440Ma)斑岩成矿受控于古亚洲洋早古生代时期俯冲增生作用;而中生代斑岩钼集中爆发成矿则分别受控于古亚洲洋体系后碰撞(~250Ma)、蒙古—鄂霍茨克洋体系同俯冲(248~204Ma)、古太平洋体系同俯冲(195~145Ma)及中国东部岩石圈减薄事件(145~106Ma)不同地球动力学体制。成矿流体方面总体而论,中亚斑岩型矿床热液蚀变遵循经典Lowell and Guibert模式,高氧化性岩浆流体有效出溶造就了大型- 超大型斑岩矿床。中亚成矿域斑岩铜矿的成矿斑岩岩石类型与环太平洋域成矿斑岩类似,以钙碱性和高钾钙碱性成分为主,最常见的是石英二长闪长岩、二长花岗岩、花岗闪长岩和花岗岩。成钼矿斑岩比成铜(- 金- 钼)斑岩更偏酸性,具更高SiO2含量。部分斑岩具埃达克质岩微量元素地球化学特征,另一部分斑岩却有类似正常弧火山岩的特征。虽然现有弧环境斑岩岩浆产生的‘MASH’和‘板片熔融’模型以及‘后碰撞拆沉与新生基性下地壳熔融’模型能够解释中亚成矿域部分斑岩铜矿床成矿的深部机制,但本文新提出‘残余洋中脊俯冲+预富集基性下地壳熔融’模型解释哈萨克斯坦成矿省巴尔喀什—西准噶尔成矿带斑岩铜大规模成矿的深部机制。中亚域斑岩钼成矿与古老地壳或古老岩石圈地幔的熔融无关,而与新生地壳熔融产生长英质岩浆的深部事件存在直接成因联系。西段哈萨克斯坦省新生地壳由古生代古亚洲洋演化过程中弧增生事件形成,而东段中国东北成矿省新生地壳则是新元古代与Rodinia超大陆相关聚合和裂解事件造就的。“新生下地壳部分熔融成钼”模型突破了钼成矿与古老地壳熔融有关的传统认识,能很好地解释全球最大的中国东北钼成矿省的成矿深部动力学机制。

    Abstract:

    A series of porphyry- type Cu(- Au), Mo, and Cu(- Mo) deposits occur in the Central Asian metallogenic domain (CAMD), the outline of which almost overlaps with that of the most typical accretionary orogenic belt with Phanerozoic crustal growth in the world—the Central Asian Orogenic Belt (CAOB) and is located between the East Europe, Siberia, Tarim and North China cratons. The characteristics of porphyry- type mineralization in the CAMD vary distinctly from the west to the east and can be summarized as having the feature of “Paleozoic copper deposits occurring in the western segment and Mesozoic molybdenum deposits in the east”. On the basis of the systematic studies on Precambrian basements, metallogenic tectonic backgrounds and porphyrytype mineralization characteristics,the CAMD can be subdivided into three metallogenic provinces according to tectonic line boundaries:the Kazakhstan Cu(- Au- Mo), the Mongolia Cu(- Au) and the Northeast China Mo(- Cu) metallogenic provinces.The Kazakhstan metallogenic province has definite Neo- Archean to Paleo- Proterozoic crystalline basements. And, four large- sized porphyry Cu deposits were formed during the Early Paleozoic accretionary orogenic process (481 to 440 Ma). However, most of deposits were produced by the Late Carboniferous (~330 to 295 Ma) clustering mineralization. The porphyry- type metallogenesis was dominated by the linear Paleozoic magmatic arc system extending from the Chinese Central Tianshan- Southern Yili- Kyrgyz Northern Tianshan- Central Kazakhstan- Kokchetav to Chingiz and the Kazakhstan orocline tectonic jointly in the western segment of the Paleo- Asian Ocean. The clustering porphyry- type mineralization occurred during the transformation from the accretionary orogeny to the oroclinal bending. The ~370 Ma and ~240 Ma porphyry- type mineralization of the Mongolia metallogenic province, which also has Neo- Archean to Paleo- Proterozoic crystalline basements, sporadically and locally happened during the evolution of the Tuva- Mongolia orocline. The earlier mineralization is related to the subductional and accretionary event of the Paleo- Asian Ocean under the South Gobi micro- continent and the later mineralization may be resulted from the subduction of the Mongol- Okhotsk Ocean. The Neo- Proterozoic crystalline basement and the petrological record of Pan- African events have been preserved widespread in the Northeast China metallogenic province. The Ordovician porphyry- type mineralization (482~440 Ma) was controlled by the subductional accretionary event of the Paleo- Asian Ocean in early Paleozoic. Whereas, the Mesozoic clustering mineralization of porphyry Mo deposits was dominated by different geodynamic processes that were associated with the post- collisional process of the Paleo- Asian Ocean (~250 Ma), the syn- subductional tectonics of the Mongol- Okhotsk Ocean (248~204 Ma), the syn- subductional process of the Paleo- Pacific Ocean (195~145 Ma) and the lithospheric thinning in eastern China (145~106 Ma). In general, the alteration and fluid characteristics of porphyry- type deposits in the CAMD are following the classic model summarized by Lowell and Guibert. The substantial exclusion of high oxidized magmatic fluids had triggered the formation of large to super large- sized porphyry deposits. The rock type of ore- forming porphyries related to copper deposits in the CAMD resembles to that of the Circum- Pacific metallogenic domain and has a calc- alkaline to high- K calc- alkaline composition predominantly. Granite, monzonitic granite, granodiorite and quartz monzodiorite occur most commonly. The Mo ore- forming porphyry is more felsic with a higher SiO2 content, compared with that of Cu deposits. Some of porphyries have a trace element geochemical signature resembling to that of adakitic rocks while others have geochemical compositions similar to that of normal arc volcanic rocks. Even though the prevalent ‘MASH’, ‘slab melting’ and ‘post- collisional break- off and melting of juvenile lower crust’ models can be employed to interpret the genesis of some porphyry Cu deposits in the CAMD, a here newly suggested model, which is based on ‘the subduction of a relictic mid- oceanic ridge and the melting of pre- enriched mafic lower crust’, is thought to explain the deep mechanism of large- scale porphyry copper mineralization in the Balkhash- West Junggar metallogenic belt of the Kazakhstan metallogenic province. Furthermore, the Mo mineralization in the CAMD has no genetic relationship with the melting of ancient crust or lithosphere mantle. Whereas, it may be genetically associated with the deep event causing the genesis of felsic magmas as a result of the melting of juvenile lower crust. The juvenile crust in the Kazakhstan province of the western segment of the CAMD was generated by the arc accretion event associated with the evolution of the Paleo- Asian Ocean in Paleozoic while that in the Northeast China province of the eastern segment of the CAMD may be produced by the event related to the assembly and the break- up of the Rodinia in Neo- Proterozoic. The ‘Mo- mineralization resulting from the partial melting of juvenile lower crust’ model has innovated the Mo metallogenic theory which is related to the melting of ancient crust and can explain the deep dynamic mechanism of mineralization in the Northeast China, the largest Mo metallogenic province in the world, successfully.

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高俊,朱明田,王信水,洪涛,李光明,李继磊,肖文交,秦克章,曾庆栋,申萍,徐兴旺,张招崇,周建波,赖勇,张晓晖,孙景贵,万博,王博.2019.中亚成矿域斑岩大规模成矿特征:大地构造背景、流体作用与成矿深部动力学机制[J].地质学报,93(1):24-71.
GAO Jun, ZHU Mingtian, WANG Xinshui, HONG Tao, LI Guangming, LI Jilei, XIAO Wenjiao, QIN Kezhang, ZENG Qingdong, SHEN Ping, XU Xingwang, ZHANG Zhaochong, ZHOU Jianbo, LAI Yong, ZHANG Xiaohui, SUN Jinggui, WAN Bo, WANG Bo.2019. Large- scale porphyry- type mineralization in the Central Asian metallogenic domain: tectonic background, fluid feature and metallogenic deep dynamic mechanism[J]. Acta Geologica Sinica,93(1):24-71.

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  • 收稿日期:2018-11-10
  • 最后修改日期:2019-01-02
  • 录用日期:2019-01-03
  • 在线发布日期: 2019-01-08
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