【摘要】：遼東寬甸和三家子地區(qū)遼河群中廣泛存在花崗質(zhì)偉晶巖脈或巖體,對(duì)其進(jìn)行研究具有重要的構(gòu)造意義。本文對(duì)兩個(gè)地區(qū)侵入遼河群中的花崗偉晶巖樣品進(jìn)行巖石學(xué)、鋯石LA-ICP-MS稀土微量元素和U-Pb定年的綜合研究,獲得侵入不同巖組地層中偉晶巖的原巖年齡,并對(duì)其成因和構(gòu)造環(huán)境進(jìn)行了探討�；◢弬ゾr主要礦物組合為石英+鉀長(zhǎng)石±鈉長(zhǎng)石±電氣石±白云母,中粗粒結(jié)構(gòu)或偉晶結(jié)構(gòu),塊狀構(gòu)造。寬甸地區(qū)侵入高家峪組大理巖中的二處偉晶巖樣品年齡分別為1842±7Ma和1864±8Ma;三家子地區(qū)侵入里爾峪組地層的二處偉晶巖樣品年齡分別為1876±11Ma和1871±7Ma,侵入大石橋組的偉晶巖巖體年齡為1802±15Ma,侵入蓋縣組地層的偉晶巖年齡為1740±8Ma。寬甸地區(qū)偉晶巖(年齡1.86~1.84Ga)鋯石陰極發(fā)光具振蕩環(huán)帶,Th/U大多0.1,稀土配分模式主要顯示巖漿鋯石的特征,在Ce/Ce*-(Sm/La)_N圖解上顯示近巖漿鋯石區(qū)域,花崗偉晶巖脈熔體可能是母巖漿初步結(jié)晶分異后的產(chǎn)物,較大保留了母巖漿的性質(zhì);三家子地區(qū)3個(gè)樣品(年齡1.87~1.74Ga)鋯石微區(qū)具低亮度無(wú)結(jié)構(gòu)特征、Th/U0.1,稀土配分模式顯示熱液鋯石特征,在Ce/Ce*-(Sm/La)_N圖解上偏熱液鋯石區(qū)域,此花崗偉晶巖脈可能是母巖漿高度結(jié)晶分異后的殘余熱液結(jié)晶而成,偏熱液性質(zhì)。三家子1個(gè)樣品(年齡1.87Ga)鋯石具弱振蕩環(huán)帶,ΣREE值較低,Eu/Eu*主要介于0.00~0.60,HREE總量低且平緩,顯示深熔成因,其偉晶巖脈熔體可能直接來(lái)自含石榴石的原巖部分熔融而成的深熔脈體。本文研究的多期次花崗偉晶巖或與遼吉造山帶周圍1.89~1.82Ga的S型或I型花崗巖和深熔脈體具有親緣關(guān)系,即大部分偉晶巖可能與1.89~1.82Ga的花崗質(zhì)巖漿作用有關(guān),一部分則與變質(zhì)沉積巖系的深熔作用有關(guān)。從構(gòu)造環(huán)境來(lái)看,遼吉造山帶在碰撞后的構(gòu)造折返過(guò)程中,從~1.87Ga到~1.74Ga至少130Myr的時(shí)間里一直處于伸展的構(gòu)造機(jī)制。在主期花崗質(zhì)巖漿上涌之后,大量殘余巖漿或深熔脈體上涌至遼河群地層中形成偉晶巖的巖脈、巖墻或巖體。
[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 鹵albite 鹵tourmaline 鹵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 鹵7Ma and 1864 鹵8 Marespectively. The age of pegmatite samples in the second part of the Liyu formation is 1876 鹵11Ma and 1871 鹵7Ma. the age of the pegmatite intruded into the Dashiqiao formation is 1802 鹵15Ma. and the pegmatite age of the Gexian formation is 1740 鹵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.
【作者單位】： 中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所;
【基金】：國(guó)家自然科學(xué)基金重點(diǎn)項(xiàng)目(41430210) 中國(guó)地質(zhì)調(diào)查局地質(zhì)大調(diào)查項(xiàng)目(DD20160121) 中國(guó)地質(zhì)科學(xué)院地質(zhì)研究所基本科研業(yè)務(wù)經(jīng)費(fèi)(J1612、YYWF201703)聯(lián)合資助
【分類號(hào)】：P588.131;P597.3

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