东准噶尔卡拉麦里断裂以南幔源底侵体、“钉合花岗岩体”的发现及其地质意义
发布时间：2018-10-18 16:03
【摘要】：新疆富蕴县滴水泉-畜牧办侵入体出露于卡拉麦里断裂以南,呈北西西向带状分布,以碱长花岗岩体为主,也可见规模较小的角闪辉长岩体。碱长花岗岩体的岩石组合为碱长花岗斑岩+碱长花岗岩,高硅(SiO_2=71.07%~76.71%),富碱(Na_2O+K_2O=7.41%~9.07%)、K_2ONa_2O(平均为1.10),显示出A型花岗岩的特点。角闪辉长岩体涌动侵入于碱长花岗岩体之中,二者接触带附近发育浆混性质的石英闪长岩。辉长岩+花岗岩的双峰式岩石组合、构造判别图解R2-R1及区域地质背景指示滴水泉侵入体形成于陆内伸展环境,且花岗岩体具有"钉合岩体"的作用,穿插了卡拉麦里蛇绿岩带。结合岩体的LA-ICP-MS锆石年龄(碱长花岗岩的206Pb/238U加权平均年龄为321±2Ma,角闪辉长岩的206Pb/238U加权平均年龄为319±3Ma)可知,卡拉麦里洋盆在晚石炭世早期(321Ma)之前已经闭合。同位素及微量元素特征显示,碱长花岗岩为年轻地壳部分熔合融的产物,而角闪辉长岩则来源于亏损的软流圈地幔及俯冲交代的地幔楔物质,代表了同期花岗岩的底侵岩浆演化的产物。辉长岩与花岗岩相似的εNd(t)值及明显的岩浆混合作用表明该区的花岗岩体并非来源于底侵岩浆的高度分异或底侵体的部分熔融,而最可能为底侵体之上的年轻地壳的部分熔融,这一结论与最近一些学者研究的断裂以北的花岗岩体成因机制相同。晚石炭世早期幔源底侵体的发现,为卡拉麦里地区后碰撞花岗岩类的幔源底侵作用提供了可靠的地质依据。
[Abstract]:The Dishui Quan-Livestock Office intrusive body in Fuyun County Xinjiang is exposed to the south of the Kalamaili fault and distributes in the north west and west direction with the alkali feldspar granite as the main body and the smaller hornblende gabbro body. The alkali feldspar granite is composed of alkali-feldspar porphyry, high SiO_2=71.07%~76.71%, Na_2O K _ 2O _ 1 7.41 ~ 9.07% and K_2ONa_2O (an average of 1.10), showing the characteristics of A-type granite. The hornblende gabbro intruded into the alkali feldspar granite and magma mixed quartz diorite was developed near the contact zone between the two bodies. The bimodal rock assemblage of gabbro granites, the tectonic discriminant R2-R1 and the regional geological background indicate that the Dishui spring intrusion was formed in the intracontinental extensional environment, and the granite body has the function of "nailing rock mass", which is inserted into the Kalamaili ophiolite belt. Combined with the LA-ICP-MS zircon age (206Pb/238U weighted mean age of 321 卤2Mafor alkali feldspar granites and 319 卤3Ma for hornblende gabbro), the Kalamori ocean basin was closed prior to the early late Carboniferous (321Ma). Isotopic and trace element characteristics indicate that alkali feldspar granite is the product of partial fusion of young crust, while hornblende gabbro is derived from depleted asthenospheric mantle and subducted mantle wedge material. It represents the product of the evolution of underplating magma in the same period of granite. The similar 蔚 Nd (t) values of gabbro to granite and obvious magmatic mixing indicate that the granitic bodies in this area are not derived from the high differentiation of the underplating magma or from the partial melting of the underplating magma, but most likely from the partial melting of the young crust above the underplating magma. This conclusion is the same as the genetic mechanism of the granite body north of the fault studied recently by some scholars. The discovery of mantle-derived transgressions in the early late Carboniferous provides a reliable geological basis for mantle-derived transgressions of post-collisional granites in the Kalamaili area.
【作者单位】： 中国地质大学地球科学学院;天津地质矿产研究所;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：中国地质调查局计划项目(1212011120508)资助
【分类号】：P588.12
[Abstract]:The Dishui Quan-Livestock Office intrusive body in Fuyun County Xinjiang is exposed to the south of the Kalamaili fault and distributes in the north west and west direction with the alkali feldspar granite as the main body and the smaller hornblende gabbro body. The alkali feldspar granite is composed of alkali-feldspar porphyry, high SiO_2=71.07%~76.71%, Na_2O K _ 2O _ 1 7.41 ~ 9.07% and K_2ONa_2O (an average of 1.10), showing the characteristics of A-type granite. The hornblende gabbro intruded into the alkali feldspar granite and magma mixed quartz diorite was developed near the contact zone between the two bodies. The bimodal rock assemblage of gabbro granites, the tectonic discriminant R2-R1 and the regional geological background indicate that the Dishui spring intrusion was formed in the intracontinental extensional environment, and the granite body has the function of "nailing rock mass", which is inserted into the Kalamaili ophiolite belt. Combined with the LA-ICP-MS zircon age (206Pb/238U weighted mean age of 321 卤2Mafor alkali feldspar granites and 319 卤3Ma for hornblende gabbro), the Kalamori ocean basin was closed prior to the early late Carboniferous (321Ma). Isotopic and trace element characteristics indicate that alkali feldspar granite is the product of partial fusion of young crust, while hornblende gabbro is derived from depleted asthenospheric mantle and subducted mantle wedge material. It represents the product of the evolution of underplating magma in the same period of granite. The similar 蔚 Nd (t) values of gabbro to granite and obvious magmatic mixing indicate that the granitic bodies in this area are not derived from the high differentiation of the underplating magma or from the partial melting of the underplating magma, but most likely from the partial melting of the young crust above the underplating magma. This conclusion is the same as the genetic mechanism of the granite body north of the fault studied recently by some scholars. The discovery of mantle-derived transgressions in the early late Carboniferous provides a reliable geological basis for mantle-derived transgressions of post-collisional granites in the Kalamaili area.
【作者单位】： 中国地质大学地球科学学院;天津地质矿产研究所;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：中国地质调查局计划项目(1212011120508)资助
【分类号】：P588.12
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