西秦岭下三叠统江里沟组构造环境和物源特征
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本文为国家重点研发计划深地资源勘查开采专项“深部矿产资源三维找矿预测评价示范”课题(编号:2017YFC0601506)“甘肃省玛曲—合作地区资源潜力评价与深部找矿预测示范”专题;甘肃省基础地质调查研究项目“甘肃玛曲—合作整装勘查区深部找矿预测”;中国地质调查局项目“甘肃省夏河—合作地区金矿整装勘查区矿产调查与找矿预测”(编号:1212010000016090160、1212010000016090149)的成果


Tectonic setting and provenance characteristics of the Lower Triassic Jiangligou Formation in West Qinling——Constraints from geochemistry of clastic rocks and U- Pb geochronology of detrital zircon
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    摘要:

    甘肃省夏河—合作地区是西秦岭重要的金矿富集区之一,下三叠统江里沟组是区内主要的赋矿地层,主要岩性有长石砂岩、泥质板岩。砂板岩中SiO2=53. 2%~69. 34%,平均值62. 36%; Al2O3=10. 80%~17. 46%,平均值14. 20%;FeO=0. 45%~4. 85%,平均值3. 31%; CaO=1. 92%~7. 66%,平均值3. 59%。稀土元素总量较高,REE=117. 97×10-6~258. 93×10-6,平均=179. 98×10-6。经球粒陨石标准化,曲线明显右倾,富集轻稀土元素,δEu=0. 55~0. 77,平均值0. 65,具有明显的负异常;经北美页岩标准化,可见曲线近似平行略向右倾斜,δEu=0. 85~1. 18,平均值1. 00,不具有异常。锆石的年龄范围为260~2594 Ma,主要集中在印支期—海西期(峰值276 Ma、391 Ma)、加里东期(峰值463 Ma)、古元古代—新太古代(峰值1866 Ma、2501 Ma)三个阶段。通过碎屑岩主微量元素地球化学、碎屑锆石UPb年龄谱系、结合区域地质背景综合判断,江里沟组源区的构造环境主要呈现出大陆岛弧、活动大陆边缘的特征,物源主要是来自上地壳的长英质火山岩,绝大多数来西秦岭及其邻区同期岩浆岩,部分来自北秦岭构造带、祁连造山带及华北板块南缘的变质基底。本次研究为西秦岭地区构造演化提供了沉积学的证据。

    Abstract:

    Xiahe—Hezuo area in Gansu Province is one of the important gold mineralization areas in the West Qinling metallogenic area. The Lower Triassic Jiangligou Formation is the main ore bearing stratum in the area which is mainly composed of feldspathic sandstone and argillaceous slate, referred as a set of fine clastic flysch formation of semi deep sea slope facies. SiO2 are ranging from 53.2% to 69.34%, with an average of 62.36%; Al2O3 are ranging from 10.80% to 17.46% ,with an average of 14.20%; FeO are ranging from 0.45% to 4.85% with an average of 3.31%; and CaO are ranging from 1.92% to 7.66% with an average of 3.59%, respectively. The total amount of rare earth elements (REE) is relatively high, and the average value is 179.98×10-6. In the chondrite- normalized diagram, the samples are characterized by enrichment in light rare earth elements (LREE), and obvious negative Eu anomaly with δEu varying from 0.55 to 0.77. Comparatively speaking, the enrichment in LREE and Eu anomaly (δEu=0.85~1.18) are not obvious in the North American shale- normalized REE distribution diagram. Furthermore, the zircon geochronological studies showed that there are some age clusters in the studied clastic rock samples including the Paleoproterozoic—Neoproterozoic (peaking at 1866 Ma and 2501 Ma), Caledonian (peaking at 463 Ma), and Indosinian—Hercynian (peaking at 276 Ma and 391 Ma). Based on the geochemical features of the clastic rocks and the age data, the tectonic setting of the source area of the Jiangligou Formation could be referred to as the continental island arc and the active continental margin. The source materials of the Jiangligou Formation clastic rocks are mainly from the felsic volcanic rocks which are majorly the contemporaneous magmatic rocks from the West Qinling Mountains and adjacent areas, and some are from the basement rocks of the North Qinling structural belt, Qilian Orogenic Belt and south margin of the North China Craton.

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引用本文

曾俊杰,李康宁,严康,韦乐乐,火兴达,张健鹏.2021.西秦岭下三叠统江里沟组构造环境和物源特征[J].地质论评,67(1):69-83,[DOI].
ZENG Junjie, LI Kangning, YAN Kang, Wei Lele, HUO Xingda, ZHANG Jianpeng.2021. Tectonic setting and provenance characteristics of the Lower Triassic Jiangligou Formation in West Qinling——Constraints from geochemistry of clastic rocks and U- Pb geochronology of detrital zircon[J]. Geological Review,67(1):69-83.

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  • 收稿日期:2020-07-15
  • 最后修改日期:2020-11-28
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  • 在线发布日期: 2021-01-19
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