秦岭岩群东段马山口岩体年代学及岩石地球化学:对北秦岭新元古代早期构造演化的指示  

Geochronology and geochemistry of the Mashankou pluton in theeastern Qinling Group:implications for the Early Neoproterozoictectonic evolution of the North Qinling orogeny

作　　者：宫相宽 陈丹玲[2] 任云飞[2] 罗芬红 谭俊 木热地力·买合苏提 李阔 GONG Xiangkuan;CHEN Danling;REN Yunfei;LUO Fenhong;TAN Jun;MUREDILI Maihesuti;LI Kuou(Xinjiang Key Laboratory for Geodynamic Processes and MetaLLogenic Prognosis of the Central Asian Orogenic Belt,College of Geology and Mining Engineering,Xinjiang University,Urumqi,Xinjiang 830046,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an,Shaanxi 710069,China)

机构地区：[1]新疆中亚造山带大陆动力学与成矿预测自治区重点实验室,新疆大学地质与矿业工程学院,新疆乌鲁木齐830046 [2]西北大学大陆动力学国家重点实验室,西北大学地质学系,陕西西安710069

出　　处：《地质学报》2022年第6期2001-2020,共20页Acta Geologica Sinica

基　　金：新疆维吾尔自治区高校科研计划项目(编号XJEDU2021Y012);新疆维吾尔自治区自然科学基金项目(编号2019D01C030);国家自然科学基金项目(编号41962013)联合资助成果。

摘　　要：河南西峡地区马山口岩体出露于北秦岭构造带秦岭岩群东段,岩石类型为片麻状花岗闪长岩。LA-ICP-MS锆石U-Pb定年结果表明,该岩体形成时代为929±7 Ma,是新元古代早期花岗质岩浆活动的产物。岩石的SiO_(2)和Al_(2)O_(3)含量分别为65.52%~66.91%和14.63%~15.41%,Na_(2)O和K_(2)O含量较高,分别为2.82%~3.08%和2.14%~3.10%,Na_(2)O/K_(2)O比值主体>1,富TFe_(2)O_(3)(5.99%~7.03%),高CaO(2.78%~3.72%)和MgO(1.35%~1.87%),Mg^(#)值介于34.4~38.3之间,A/CNK值为1.07~1.14,属于过铝质钙碱性—高钾钙碱性岩石,显示I型花岗岩特征。岩石的Nb/Ta、Rb/Y和Nb/Y比值反映壳源岩石特征,低Sr(102×10^(-6)~175×10^(-6)),高Yb(2.13×10^(-6)~3.67×10^(-6))和Y(27.0×10^(-6)~38.6×10^(-6)),可能是下地壳(变)基性岩石部分熔融的产物。岩石稀土总量中等(∑REE=180×10^(-6)~229×10^(-6)),相对富集轻稀土和大离子亲石元素Rb、Ba、Th等,亏损高场强元素Nb、Ta和Ti,具有火山弧花岗岩地球化学特征,形成于新元古代早期洋壳俯冲背景下的陆缘弧环境。The Mashankou pluton in the eastern part of the Qinling Group in the North Qinling terrane,located in the Xixia area,Henan Province,is mainly composed of gneissic grandiorite.LA-ICP-MS zircon U-Pb dating shows that the pluton was formed at 929±7 Ma.The SiO_(2) and Al_(2)O_(3) contents of the grandiorites are 65.52%~66.91%and 14.63%~15.41%,respectively.They have high contents of Na_(2)O(2.82%~3.08%),K_(2)O(2.14%~3.10%),TFe_(2)O_(3)(5.99%~7.03%),CaO(2.78%~3.72%)and MgO(1.35%~1.87%),with Na_(2)O/K_(2)O ratios>1,A/CNK values of 1.07~1.14 and Mg^(#) values ranging from 34.4 to 38.3.The grandiorites belong to peraluminous calc-alkaline and high-K calc-alkaline rocks,and show features of I-type granites.They are characterized by low content of Sr(102×10^(-6)~175×10^(-6)),high content of Yb(2.13×10^(-6)~3.67×10^(-6)) and Y(27.0×10^(-6)~38.6×10^(-6)),with low Nb/Ta,Rb/Y and Nb/Y ratios,indicating that the grandiorites may be products of partial melting of basaltic rocks in the lower crust.The rocks have moderate REE contents(∑REE=180×10^(-6)~229×10^(-6)),and are enriched in LREE and LILE such as Rb,Ba and Th,and depleted in HFSE such as Nb,Ta and Ti.They have the geochemical characteristics of volcanic arc granite and were formed in the Neoproterozoic continental marginal arc environment.

关 键 词：秦岭岩群 新元古代花岗岩 锆石U-PB年代学 岩石地球化学 陆缘弧 

分 类 号：P534.3[天文地球—古生物学与地层学] P597.3[天文地球—地质学] P542