内蒙古梅劳特乌拉蛇绿岩中埃达克岩的发现及其演化模式

发布时间：2018-12-14 21:25

【摘要】：本文报道在内蒙古西乌旗梅劳特乌拉SSZ型蛇绿岩中新发现的早二叠世洋内弧呼和德埃达克岩。该埃达克岩位于贺根山缝合带内,侵位于晚石炭世梅劳特乌拉SSZ型蛇绿岩带之中,岩性为细粒-中粒花岗闪长岩。锆石LA-ICP-MS U-Pb测年表明,呼和德埃达克岩的侵位年龄为294.7±1.7Ma,其形成时代为早二叠世。呼和德埃达克岩属于低钾拉斑系列与中钾钙碱性系列的过渡型岩石,SiO_2为64.93%~69.50%,MgO为0.80%~1.48%,Al_2O_3为15.72%~19.11%,Na2O/K2O为3.01~8.60;Sr为368×10~(-6)~700.40×10~(-6),Yb为0.95×10~(-6)~1.76×10~(-6),Y为5.26×10~(-6)~9.27×10~(-6);相对富集大离子亲石元素(LILE)K、Rb和Sr等,亏损高场强元素(HFSE)Nb、Ta、Zr、Ti和P等;稀土元素总量较低(32.68×10~(-6)~66.69×10~(-6)),轻重稀土分馏明显,(La/Yb)N为3.31~5.10,无明显的Eu负异常,显示了典型埃达克岩的地球化学特征。呼和德埃达克岩与梅劳特乌拉SSZ型蛇绿岩,构成梅劳特洋内弧初始俯冲作用较为完整连续的蛇纹石化方辉橄榄岩、层状-块状辉长岩、枕状拉斑玄武岩、玻安岩、富Nb玄武岩和高镁或镁安山岩等岩石组合序列。岩石学和地球化学特征表明,呼和德埃达克岩形成于洋内弧环境,为洋内弧初始俯冲作用早期的深成岩。这标志着古亚洲洋贺根山缝合带洋壳初始俯冲发生于早二叠世。根据晚石炭世-早二叠世梅劳特乌拉洋内弧的主要特征和识别标志,初步建立了晚石炭世-早二叠世梅劳特乌拉洋内弧初始俯冲系统形成演化模式。
[Abstract]:This paper reports the discovery of the early Permian Intraoceanic Arc Hugh and de Edark rocks in the Merlot Ula type ophiolite of Xiwu Banner, Inner Mongolia. The adakite is located in the Hegenshan suture zone and transgressive in the late Carboniferous Merlot Ula SSZ ophiolite belt with fine grained and medium grain granodiorite. The zircon LA-ICP-MS U-Pb dating indicates that the emplacement age of the Huhe Dadakite is 294.7 卤1.7 Ma.The age of its formation is early Permian. The Huhe Adakite is a transitional rock of the low potassium plagitic series and the middle potassium calc-alkaline series. The SiO_2 is 64.93 and 69.50. The SiO_2 is 0.80 and 1.48. The number of Al2O3 is 15.72 and 19.11. Na2O/K2O was 3.01 and 8.60; The Sr ranges from 368 脳 10 ~ (-6) to 700.40 脳 10 ~ (-6), Yb: 0.95 脳 10 ~ (-6) ~ 1.76 脳 10 ~ (-6), Y, 5.26 脳 10 ~ (-6) ~ 9.27 脳 10 ~ (-6), Y; Large ion lithophile elements such as (LILE), RB and Sr are relatively enriched, and high field strength elements such as (HFSE) Nb,Ta,Zr,Ti and P are depleted. The total amount of rare earth elements is lower (32.68 脳 10 ~ (-6) ~ 66.69 脳 10 ~ (-6), heavy rare earth fractionation is obvious, (La/Yb) N is 3.31 ~ 5.10, and there is no obvious negative Eu anomaly, which shows the geochemical characteristics of typical adakite. The Huhe Edakite and the Merlot Ula SSZ ophiolite form a relatively complete and continuous initial subduction of the Merlot ocean arc, which is composed of serpentine pyroxenite, layered and massive gabbro, occipital tholeiitic basalt, and Bollite. Nb-rich basalt and high-magnesium or mafic-andesite assemblage sequences. The petrological and geochemical characteristics indicate that the Huhe Dadakite formed an inner arc environment of Yu Yang, which is a deep diagenetic rock in the early stage of the initial subduction of the intraoceanic arc. This indicates that the initial subduction of the oceanic crust occurred in the early Permian. According to the main characteristics and identification criteria of the inner arc of the Merlot Ula Ocean in the late Carboniferous and early Permian, the evolution model of the initial subduction system of the inner arc of the Merlot Ula Ocean in the late Carboniferous and the early Permian is established.
【作者单位】：河北地质大学资源学院;
【基金】：国家自然科学基金(批准号:41502211) 中国地质调查局“内蒙古1∶5万高力罕牧场三连等四幅区调(编号:1212011120711) 河北省教育厅科技项目(编号:ZC20165013)资助的成果
【分类号】：P588.12

【相似文献】