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徐容,邓军,程韩宇,崔晓琳,王传斌. 2018. 华南板块西缘和腾冲-保山地块晚白垩世岩浆活动及Sn成矿作用对比:年代学、地球化学和动力学背景. 岩石学报, 34(5): 1271-1284
华南板块西缘和腾冲-保山地块晚白垩世岩浆活动及Sn成矿作用对比:年代学、地球化学和动力学背景
作者单位E-mail
徐容 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
邓军 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083 djun@cugb.edu.cn 
程韩宇 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
崔晓琳 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
王传斌 中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083  
基金项目:本文受国家重点基础研究发展计划"973"项目(2015CB452606)、国家重点研发计划(2016YFC0600307)和国家自然科学青年基金项目(41602090)联合资助.
摘要:
      华南板块西缘和西南三江腾冲-保山地块发育我国两个重要的Sn成矿带。两个带大规模岩浆活动和Sn成矿作用在年代学和地球化学特征等方面具有相似性。它们的成岩-成矿年龄时限均在晚白垩世,分别为78.9~60.0Ma和108.0~74.1Ma,分别集中在76.0~62.0Ma和98.0~82.0Ma,自西向东总体显示逐渐变老的趋势。晚白垩世成矿相关的岩浆岩均属于花岗质岩类,表现出高硅、富铝、富钾,富集轻稀土而亏损重稀土,相对富集Rb、Th、U而相对亏损Ba、Nb、Sr、Ti,具明显的Eu负异常,初始锶值(87Sr/86Sr)i集中在0.7038~0.7283,同时具有低的εNdt)值(-11.6~-6.9)和εHft)值(-18.1~1.2),反映岩浆岩主要起源于地壳。本文分析结果联合区域地质证据表明,腾冲-保山地块晚白垩世处于新特提斯洋俯冲环境;华南板块西缘岩石圈伸展可能受控于东侧太平洋俯冲回撤的远程效应,也可能系西侧新特提斯洋俯冲回撤的响应,抑或二者联合作用的结果。基于华南板块西缘和腾冲-保山地块的成岩-成矿年龄和岩体地球化学特征的类似性和空间差异变化,本文提出新特提斯洋俯冲联合作用模型:即华南板块西缘晚白垩世成岩-成矿活动也可能受控于特提斯构造域,为新特提斯洋俯冲后在板块逐渐回撤的过程中自东向西逐渐诱发晚白垩世广西西缘、云南东南部软流圈上涌和腾冲、保山地壳减压熔融,进而导致岩浆活动和大规模Sn成矿作用。该模型对于丰富晚白垩世西南三江-华南西缘跨区域成岩成矿构造环境提供了新认识。
英文摘要:
      Two important Sn metallogenic belts are developed in the western South China and the Tengchong-Baoshan regions. The large-scale magmatism and related Sn mineralization in the two belts share many similarities in geochronological and geochemical signatures. The Late Cretaceous intrusions and Sn deposits in the two regions mainly formed in 78.9~60.0Ma and 108.0~74.1Ma, with peaks of 76.0~62.0Ma and 98.0~82.0Ma, respectively and show a younging trend from east to west. The intrusions related to the Late Cretaceous mineralization have typical granitic composition and are characterized by high SiO2 contents, high Al2O3 and K2O contents, slight enrichment in LREE with pronounced negative Eu anomalies, enrichment in Rb, Th and U, and depletion in Ba, Nb, Sr and Ti; they also have initial 87Sr/86Sr ratios ranging from 0.7038 to 0.7283 and relatively low εNd(t) values (-11.6 to -6.9) and εHf(t) value (-18.1 to +1.2). All the above features indicate an dominantly crustal origin. A comprehesive review in this paper combined with the regional geological evidence demonstrates that the Tengchong-Baoshan region was controlled by the subduction of the Neo-Tethyan Ocean in the Late Cretaceous, whereas the lithospheric extension in the western South China may have been controlled either by the remote effect of the rollback of the subducted Pacific oceanic plate in the east or by the rollback of the subducted Neo-Tethyan oceanic plate in the west, or else, by a joint action. By comparing the similarities and spatial differences of the ages and geochemical characteristics in the two regions, we suggest a joint Neo-Tethyan Ocean subduction tectonic model:the magmatism and Sn mineralization in the western South China could have been controlled by Tethyan tectonic domain, including the Neo-Tethyan Ocean flat-slab subduction, slab rollback and intracontinental back-arc extension that triggered the asthenosphere upwelling in the western South China, and crustal decompression and melting in the Tengchong-Baoshan regions. This model provides a new insight into the Late Cretaceous cross-regional tectonic setting of the magmatism and Sn mineralization in the western margin of South China and the Tengchong-Baoshan regions.
关键词:锡成矿  岩浆活动  动力学背景  华南板块西缘  腾冲-保山地块
投稿时间:2018-01-30  修订日期:2018-04-23
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主办单位:中国矿物岩石地球化学学会
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