钦-杭结合带南段新元古代俯冲作用:来自粤西贵子混杂岩变基性岩年代学和地球化学的证据

发布时间：2018-05-10 13:01

本文选题：钦-杭结合带 + 新元古代俯冲体系　；参考：《岩石学报》2017年03期

【摘要】：新元古代以来,扬子地块和华夏地块拼贴形成钦-杭结合带。粤西贵子混杂岩为揭示钦-杭结合带南段地质演化提供了一个重要的窗口。贵子混杂岩构造岩块为强烈变形-变质的变基性岩、深海硅质岩,基质为石英岩、云母片岩以及具鲍马序列富锰质硅泥质岩等。对混杂岩中变基性岩年代学和元素地球化学分析显示,锆石U-Pb年龄为948±11Ma,除少部分属低钾(拉斑)外,其余均为钙碱性系列,CIPW标准矿物成分属石英拉斑玄武岩-橄榄拉斑玄武岩组合。变基性岩具有高TiO_2(平均1.85%)、P_2O_5(平均0.21%)的特点;无Eu异常或轻微负异常,配分曲线右倾(球粒陨石标准化(La/Yb)N=2.65~3.89),大离子亲石元素(Rb、Ba、Th、U)富集,高场强元素(Nb、Zr、Hf)轻微亏损,表现为洋壳消减作用下岛弧岩浆岩特征。高的Nb(7.56×10~(-6)~16.11×10~(-6),均大于7×10~(-6))、Nb/U(18.39~25.65)、(Nb/La)N(0.76~0.94,原始地幔标准化)显示为岛弧环境富Nb玄武岩。本研究认为,云开地块出露的这套构造混杂岩,是新元古代古华南洋俯冲在钦-杭结合带南段的记录,可为该带的南东边界提供线索。
[Abstract]:Since the Neoproterozoic, the Yangtze and Huaxia blocks have been collaged to form the Qinghang combined belt. The Guizi melange in western Guangdong provides an important window for revealing the geological evolution of the southern section of the Qinghang combined belt. The tectonic block of Guizi melange is characterized by strong deformation-metamorphic basic rocks, deep-sea siliceous rocks, quartzite, mica schist and boma sequence manganese-rich siliceous mudstone. The geochronology and elemental geochemistry analysis of metamorphic rocks in the melange show that the zircon U-Pb age is 948 卤11 Ma, except for a small number of low potassium (lacquer). The rest are CIPW standard mineral compositions belonging to quartz tholeiite-olivine tholeiite assemblage. The metamorphic rocks are characterized by high tio _ 2 (average 1.85 / P _ 2O _ 5 (mean 0.21), no EU anomaly or slight negative anomaly, right dip of the partition curve (chondrite standardization La / YbTH _ (2.65) / 3.89), large ion lithophile element RbBaThU), and a slight loss of the high field strength element, It is characterized by island arc magma under subduction of oceanic crust. The high Nb(7.56 脳 10 ~ (10) ~ (-6) ~ (1) ~ (16) 脳 10 ~ (10) ~ (10) ~ (6) N ~ (b / U) > 7 脳 10 ~ (10) ~ (6) N ~ (b / U) ~ (18. 39) ~ (25. 65) nb / L ~ (0.76) ~ (0. 94) shows that the island arc environment is NB rich in basalt. This study suggests that the tectonic melange exposed from the Yunkai block is a record of the subduction of the Neoproterozoic Gu Hua South Ocean in the southern part of the Qinghang combined belt, which can provide clues for the southern and eastern boundary of the belt.
【作者单位】：广东省地质过程与矿产资源探查重点实验室;中山大学地球科学与地质工程学院;中山大学地球环境与地球资源研究中心;
【基金】：国家重点研发计划重点专项项目(2016YFC0600506) 国家自然科学基金项目(41273040) 中国地质调查局项目(12120113067600 高校基本科研业务费中山大学科研助手资助计划联合资助
【分类号】：P588.145

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