辽东宽甸和三家子地区花岗伟晶岩的锆石U-Pb年代学及其地质意义
发布时间：2019-01-21 18:29
【摘要】：辽东宽甸和三家子地区辽河群中广泛存在花岗质伟晶岩脉或岩体,对其进行研究具有重要的构造意义。本文对两个地区侵入辽河群中的花岗伟晶岩样品进行岩石学、锆石LA-ICP-MS稀土微量元素和U-Pb定年的综合研究,获得侵入不同岩组地层中伟晶岩的原岩年龄,并对其成因和构造环境进行了探讨。花岗伟晶岩主要矿物组合为石英+钾长石±钠长石±电气石±白云母,中粗粒结构或伟晶结构,块状构造。宽甸地区侵入高家峪组大理岩中的二处伟晶岩样品年龄分别为1842±7Ma和1864±8Ma;三家子地区侵入里尔峪组地层的二处伟晶岩样品年龄分别为1876±11Ma和1871±7Ma,侵入大石桥组的伟晶岩岩体年龄为1802±15Ma,侵入盖县组地层的伟晶岩年龄为1740±8Ma。宽甸地区伟晶岩(年龄1.86~1.84Ga)锆石阴极发光具振荡环带,Th/U大多0.1,稀土配分模式主要显示岩浆锆石的特征,在Ce/Ce*-(Sm/La)_N图解上显示近岩浆锆石区域,花岗伟晶岩脉熔体可能是母岩浆初步结晶分异后的产物,较大保留了母岩浆的性质;三家子地区3个样品(年龄1.87~1.74Ga)锆石微区具低亮度无结构特征、Th/U0.1,稀土配分模式显示热液锆石特征,在Ce/Ce*-(Sm/La)_N图解上偏热液锆石区域,此花岗伟晶岩脉可能是母岩浆高度结晶分异后的残余热液结晶而成,偏热液性质。三家子1个样品(年龄1.87Ga)锆石具弱振荡环带,ΣREE值较低,Eu/Eu*主要介于0.00~0.60,HREE总量低且平缓,显示深熔成因,其伟晶岩脉熔体可能直接来自含石榴石的原岩部分熔融而成的深熔脉体。本文研究的多期次花岗伟晶岩或与辽吉造山带周围1.89~1.82Ga的S型或I型花岗岩和深熔脉体具有亲缘关系,即大部分伟晶岩可能与1.89~1.82Ga的花岗质岩浆作用有关,一部分则与变质沉积岩系的深熔作用有关。从构造环境来看,辽吉造山带在碰撞后的构造折返过程中,从~1.87Ga到~1.74Ga至少130Myr的时间里一直处于伸展的构造机制。在主期花岗质岩浆上涌之后,大量残余岩浆或深熔脉体上涌至辽河群地层中形成伟晶岩的岩脉、岩墙或岩体。
[Abstract]:Granitic pegmatite veins or rock bodies are widely found in Liaohe Group of Kuandian and Sanjiazi areas in eastern Liaoning Province. It is of great tectonic significance to study them. In this paper, the petrology, zircon LA-ICP-MS rare earth trace elements and U-Pb dating of granitic pegmatite samples from two intrusive Liaohe groups were studied, and the proto-rock ages of pegmatite intruded into different formations were obtained. The origin and tectonic environment are also discussed. The main mineral assemblages of granitic pegmatite are quartz potassium feldspar 卤albite 卤tourmaline 卤Muscovite, medium coarse grain structure or pegmatite structure, block structure. The age of two pegmatite samples intruding into Gaojiayu formation marble in Kuandian area is 1842 卤7Ma and 1864 卤8 Marespectively. The age of pegmatite samples in the second part of the Liyu formation is 1876 卤11Ma and 1871 卤7Ma. the age of the pegmatite intruded into the Dashiqiao formation is 1802 卤15Ma. and the pegmatite age of the Gexian formation is 1740 卤8Ma. The pegmatite (age 1.86~1.84Ga) zircon in Kuandian area is oscillating, and Th/U is mostly 0.1. The REE distribution pattern mainly shows the characteristics of magmatic zircon. The Ce/Ce*- (Sm/La) _ N diagram shows that the melt of granitic pegmatite vein may be the product of primary crystallization and differentiation of parent magma in the near magmatic zircon region, and the properties of parent magma are largely preserved. Three zircon samples (age 1.87~1.74Ga) in Sanjiazi area are characterized by low brightness and no structure. The Th/U0.1, rare earth distribution pattern shows hydrothermal zircon characteristics, and the Ce/Ce*- (Sm/La) N diagram shows the partial hydrothermal zircon region. This granitic pegmatite vein may be formed by crystallization of residual hydrothermal solution after highly crystallized differentiation of the parent magma. The zircon (age 1.87Ga) of 1 sample (age 1.87Ga) has a weak oscillatory ring zone with a low 危 REE value, and the Eu/Eu* is mainly between 0. 000 and 0. 60 HREE with a low and gentle total, indicating the origin of deep melting. The melts of pegmatite veins may come directly from the partial melting of the original rocks containing garnet. The multistage granitic pegmatite studied in this paper is related to the 1.89~1.82Ga S-type or I-type granites around the Liaoji orogenic belt and the deep-melt vein, that is, most of the pegmatite may be related to the granitic magmatism of 1.89~1.82Ga. Some of them are related to the deep melting of metamorphic sedimentary rock series. From the tectonic environment, the Liaoji orogenic belt has been in the extensional tectonic mechanism from ~ 1.87Ga to ~ 1.74Ga at least 130Myr during the post-collision tectonic reentry process. After the granitic magma upwelling in the main period, a large number of residual magma or deep melt magma body upwelled to the pegmatite vein, rock wall or rock mass in the Liaohe Group formation.
【作者单位】： 中国地质科学院地质研究所;
【基金】：国家自然科学基金重点项目(41430210) 中国地质调查局地质大调查项目(DD20160121) 中国地质科学院地质研究所基本科研业务经费(J1612、YYWF201703)联合资助
【分类号】：P588.131;P597.3
本文编号：2412913
[Abstract]:Granitic pegmatite veins or rock bodies are widely found in Liaohe Group of Kuandian and Sanjiazi areas in eastern Liaoning Province. It is of great tectonic significance to study them. In this paper, the petrology, zircon LA-ICP-MS rare earth trace elements and U-Pb dating of granitic pegmatite samples from two intrusive Liaohe groups were studied, and the proto-rock ages of pegmatite intruded into different formations were obtained. The origin and tectonic environment are also discussed. The main mineral assemblages of granitic pegmatite are quartz potassium feldspar 卤albite 卤tourmaline 卤Muscovite, medium coarse grain structure or pegmatite structure, block structure. The age of two pegmatite samples intruding into Gaojiayu formation marble in Kuandian area is 1842 卤7Ma and 1864 卤8 Marespectively. The age of pegmatite samples in the second part of the Liyu formation is 1876 卤11Ma and 1871 卤7Ma. the age of the pegmatite intruded into the Dashiqiao formation is 1802 卤15Ma. and the pegmatite age of the Gexian formation is 1740 卤8Ma. The pegmatite (age 1.86~1.84Ga) zircon in Kuandian area is oscillating, and Th/U is mostly 0.1. The REE distribution pattern mainly shows the characteristics of magmatic zircon. The Ce/Ce*- (Sm/La) _ N diagram shows that the melt of granitic pegmatite vein may be the product of primary crystallization and differentiation of parent magma in the near magmatic zircon region, and the properties of parent magma are largely preserved. Three zircon samples (age 1.87~1.74Ga) in Sanjiazi area are characterized by low brightness and no structure. The Th/U0.1, rare earth distribution pattern shows hydrothermal zircon characteristics, and the Ce/Ce*- (Sm/La) N diagram shows the partial hydrothermal zircon region. This granitic pegmatite vein may be formed by crystallization of residual hydrothermal solution after highly crystallized differentiation of the parent magma. The zircon (age 1.87Ga) of 1 sample (age 1.87Ga) has a weak oscillatory ring zone with a low 危 REE value, and the Eu/Eu* is mainly between 0. 000 and 0. 60 HREE with a low and gentle total, indicating the origin of deep melting. The melts of pegmatite veins may come directly from the partial melting of the original rocks containing garnet. The multistage granitic pegmatite studied in this paper is related to the 1.89~1.82Ga S-type or I-type granites around the Liaoji orogenic belt and the deep-melt vein, that is, most of the pegmatite may be related to the granitic magmatism of 1.89~1.82Ga. Some of them are related to the deep melting of metamorphic sedimentary rock series. From the tectonic environment, the Liaoji orogenic belt has been in the extensional tectonic mechanism from ~ 1.87Ga to ~ 1.74Ga at least 130Myr during the post-collision tectonic reentry process. After the granitic magma upwelling in the main period, a large number of residual magma or deep melt magma body upwelled to the pegmatite vein, rock wall or rock mass in the Liaohe Group formation.
【作者单位】： 中国地质科学院地质研究所;
【基金】：国家自然科学基金重点项目(41430210) 中国地质调查局地质大调查项目(DD20160121) 中国地质科学院地质研究所基本科研业务经费(J1612、YYWF201703)联合资助
【分类号】：P588.131;P597.3
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