摘要
【研究目的】为解决敦煌地块敖包山晶质石墨矿集区晶质石墨矿床研究程度较低的问题,通过对该区变质岩原岩特征及古构造环境进行深入研究,以期为该区的成矿规律研究提供地质依据。【研究方法】本文运用岩石地球化学方法对该区变质岩进行原岩恢复,探讨其形成时的古构造环境。【研究结果】二云石英片岩、黑云斜长片麻岩和斜长角闪岩均具有轻稀土富集的特征。斜长角闪岩K_(2)ONa_(2)O,富集大离子亲石元素Rb、K等,亏损Ba、Nb、Ta、Zr、Hf、Ti、Sr等元素,具有明显的Eu负异常,LREE/HREE平均值分别为12.44和8.89,轻重稀土元素分异较强烈。【结论】敖包山晶质石墨矿集区变质岩原岩形成于浅水区,水动力环境较弱。斜长角闪岩的原岩为亚碱性基性火山岩,形成于岛弧环境;二云石英片岩和黑云斜长片麻岩的原岩为页岩、黏土岩,构造环境为活动大陆边缘,古沉积环境为干燥气候带条件下富氧的海陆交互相,古水体介质为半咸水。
This paper is the result of mineral exploration engineering.[Objective]Due to the relatively low research level of crystalline graphite deposits in the Aobaoshan crystalline graphite deposit-concentrated area in Dunhuang block,the protolith restoration and paleoenvironment of this area are studied profoundly,which will provide a geological foundation for metallogenic regularity.[Methods]The protolith of the metamorphic rocks in the Aobaoshan crystalline graphite deposit-concentrated area is restored using the method of petrochemistry,and the paleotectonic environment of its formation is discussed.[Results]Two-mica quartz schist,biotite plagioclase gneiss and plagioclase amphibolite are enriched in the light rare earth elements.The plagioclase amphibolites have less K_(2)O contents than Na_(2)O.They are weakly depleted in Nb and Ta,and strong depleted in Zr and Hf,and have the ratios of LREE/HREE ranging from 2.21 to 6.97,indicating the weak fractionation degree of light and heavy rare earth elements.The biotite plagioclase gneisses and two-mica quartz schists have higher K_(2)O contents than Na_(2)O.They show the enrichment in large ion lithophile elements,such as Rb and K,and the depeletion in Ba,Nb,Ta,Zr,Hf,Ti and Sr,and obvious Eu negative anomalies.The average ratios of LREE/HREE of the biotite plagioclase gneiss and two-mica quartz schist are 12.44 and 8.89,respectively,indicating strong differentiation of light and heavy rare earth elements.[Conclusions]It is inferred that the protoliths of the metamorphic rocks from the Aobaoshan crystalline graphite deposit-concentrated area were formed in shallow water area with weak hydrodynamic environment.The protoliths of the plagioclase amphibolites in the Aobaoshan crystalline graphite deposit-concentrated area are subalkaline basic volcanic rock,and they were formed in an island arc.The protoliths of biotite plagioclase gneisses and two-mica quartz schists are shale and clayrock,and they were formed at active continental margins.The paleosedimentary environment was oxygen-rich interactive marine and terrestrial deposition in dry climate zone,and the paleowater medium was brackish water.
作者
赵吉昌
汤庆艳
柳永刚
苏天宝
王振
胡小春
杨镇熙
宋宏
张家和
ZHAO Jichang;TANG Qingyan;LIU Yonggang;SU Tianbao;WANG Zhen;HU Xiaochun;YANG Zhenxi;SONG Hong;ZHANG Jiahe(Fourth Institute of Geological and Mineral Exploraton of Gansu Provinical Bureau of Geology and Mineral Resourses,Jiuquan 735000,Gansu,China;School of Earth Sciences,Key Laboratory of Mineral Resources in Western China(Gansu Province),Lanzhou University,Lanzhou 730000,Gansu,China;Gansu Geological Exploration Fund Management Center,Lanzhou 730000,Gansu,China;Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《中国地质》
CAS
CSCD
北大核心
2023年第2期557-572,共16页
Geology in China
基金
第二次青藏高原综合科学考察研究(2019QZKK0704)
甘肃省基础地质调查项目“甘肃省酒泉市晶质石墨矿调查研究项目”(甘资勘发[2019]129号)
国家自然科学基金项目(41872073,41472070)
甘肃省科技计划项目(21JR7RA498,18JR3RA266,22JR5RA819)
兰州大学中央高校基本科研业务费专项资金(lzujbky-2021-ct07,lzujbky-2017-77)联合资助。
关键词
晶质石墨矿集区
敦煌岩群
变质岩
原岩恢复
敖包山
敦煌地块
甘肃省
crystalline graphite deposit-concentrated area
Dunhuang Group
metamorphic rocks
protolith restoration
Aobaoshan
Dunhuang block
Gansu Province
作者简介
赵吉昌,男,1984年生,教授级高级工程师,从事区域矿产地质调查及矿产勘查研究,E-mail:278717758@qq.com;通讯作者:汤庆艳,女,1986年生,教授,从事矿物学、岩石学、矿床学的教学和科研工作,E-mail:tangqy@lzu.edu.cn。
