The Liao-Ji belt(LJB)is one of the Paleoproterozoic tectonic belts located in the North China Craton.A large number of Paleoproterozoic meta-volcanic-sedimentary rock and intrusive rocks are preserved in the LJB,which...The Liao-Ji belt(LJB)is one of the Paleoproterozoic tectonic belts located in the North China Craton.A large number of Paleoproterozoic meta-volcanic-sedimentary rock and intrusive rocks are preserved in the LJB,which provide reliable carriers for the study of the Paleoproterozoic tectonic evolution of the North China Craton.The Paleoproterozoic intrusive rock in the LJB can be divided into the following seven types:syenogranite,quartz diorite,porphyry granite,migmatitic granite,sye-nite,metamorphic plutonic rock,and granitic pegmatite and metagabbro(metamorphic diabase).Zir-con U-Pb dating of 15 samples from intrusive rocks was carried out in this study.The chronology framework of the Paleoproterozoic intrusive rock in the LJB was established,and the magmatism of intrusive rocks can be divided into three stages:2200 to 2110,2010 to 1937,1900 to 1820 Ma.The chronological framework supported the evolution model of subduction accretionary arc-continent colli-sion in the LJB effectively.Combined with previous geochemical work,it was a passive continental margin environment at approximately 2200 Ma,and then transformed into and active continental margin.The bimodal intrusive rocks between 2180 and 2150 Ma indicated a back-arc tension envi-ronment which lasted until approximately 2110 Ma with a large number of basic intrusive rocks.And then the back-arc basin began to contract and the magmatic activities were reduced,with only a small number of intrusive rock activities occurring at approximately 2040,2010 and 1937 Ma.After the orogenic activities,there was a post-orogenic extension stage from 1900 to 1820 Ma.Magmatic activi-ties caused by the environmental extension started to occur more frequently and subsequently resulted in the large-scale intrusive rocks in eastern Liaoning.展开更多
Deciphering the relationship between polyphase tectonic foliations and their associated mineral assemblages is significant in understanding the process from diagenesis to low-/medium-/high-grade metamorphism.It can pr...Deciphering the relationship between polyphase tectonic foliations and their associated mineral assemblages is significant in understanding the process from diagenesis to low-/medium-/high-grade metamorphism.It can provide information related to strain,metamorphic conditions and overprinting relationships and so help reveal the tectonic evolution of orogenesis.In this study,we predominately focus on the formation of foliations and their related minerals,as developed in two separate basins.First of all,two stages of axial plane cleavages(S1 and S2)were recognized in the Hongyanjing inter-arc basin,the formation of the S1 axial plane cleavage is associated with mica rotation and elongation in mudstones in the local area.The pencil structure of S2 formed during the refolding phase,the minerals in the sedimentary rocks not changing their shape and orientation.Secondly,in the Liao-Ji backarc basin,foliations include diagenetic foliation(bedding parallel foliation),tectonic S1 foliation(secondary foliation or axial plane cleavage of S0 folding)and crenulation cleavage(S2).The formation mechanism of foliation changes from mineral rotation or elongation and mineral solution transfer in S1 to crystal-plastic deformation,dynamic recrystallization and micro-folding in S2.Many index metamorphic minerals formed from low-grade to medium-grade consist of biotites,garnets,staurolite and kyanite,constituting a typical Barrovian metamorphic belt.Accordingly,a new classification of foliation is presented in this study.The foliations can be divided into continuous and disjunctive foliations,based on the existence of microlithons,detectable with the aid of a microscope.Disjunctive foliation can be further sub-divided into spaced foliation and crenulation cleavage,according to whether(or not)crenulation(micro-folding)is present.The size of the mineral grains is also significant for classification of the foliations.展开更多
华北克拉通发育三条古元古代构造带,包括：东部陆块内部的胶-辽-吉带（Jiao-Liao-Ji belt）、西部陆块内部的孔兹岩带（Khondalite belt）以及两个陆块之间的中部造山带（Trans-North China Orogen）。通过二十多年的深入研究,在区域构...华北克拉通发育三条古元古代构造带,包括：东部陆块内部的胶-辽-吉带（Jiao-Liao-Ji belt）、西部陆块内部的孔兹岩带（Khondalite belt）以及两个陆块之间的中部造山带（Trans-North China Orogen）。通过二十多年的深入研究,在区域构造、变质地质、岩浆作用、地球化学、同位素年代学以及地球物理等方面积累了大量资料,并取得了一系列重要的科学进展。其中,胶-辽-吉带是华北克拉通最具代表性的一条古元古代造山/活动带,它不仅接受了古元古代巨量的陆壳物质沉积,而且经历了十分复杂的构造演化过程,并经受了多期岩浆-变质事件的改造。胶-辽-吉造山/活动带的物质组成最为丰富,以大面积分布的巨量（火山）沉积岩系为特征,在中国境内包括吉南地区的集安群和老岭群、辽东南地区的南辽河和北辽河群、胶北地区的荆山群和粉子山群,向南西则有可能穿越郯庐断裂延伸至徐州-蚌埠一带的五河群,总体呈NE向展布,延伸规模长约1000km。从巨量沉积岩系的岩石组合和空间分布特征来看,荆山群与南辽河群、集安群可以对比,而粉子山群则与北辽河群、老岭群相当。然而,由于多期/多阶段强烈构造变形作用的影响,原来各群、组中地层的上下层位及接触关系已完全破坏,目前均已呈规模不一的构造岩片形式叠置在一起,彼此之间呈断层或韧性剪切带接触。巨量变沉积岩系的源区物质主要来源于造山/活动带内古元古代花岗质岩石和两侧古老陆块的变质基底,原岩形成时代为1.95～2.15Ga左右。以往研究表明,胶-辽-吉造山/活动带变质作用的强度十分不均匀,（中-高压）麻粒岩相变质只局限于胶北的荆山群及相关岩石,而粉子山群以及辽东南的南、北辽河群和吉南的集安群、老岭群只经历了角闪岩相变质,局部甚至只达到绿片岩相变质。粉子山群、北辽河群和老岭群变展开更多
基金This study was financially supported by the National Key Research and Development Program(No.2018YFC0603804)the China Geological Survey(Nos.DD20190042,DD20190039 and DD20160048-05).
文摘The Liao-Ji belt(LJB)is one of the Paleoproterozoic tectonic belts located in the North China Craton.A large number of Paleoproterozoic meta-volcanic-sedimentary rock and intrusive rocks are preserved in the LJB,which provide reliable carriers for the study of the Paleoproterozoic tectonic evolution of the North China Craton.The Paleoproterozoic intrusive rock in the LJB can be divided into the following seven types:syenogranite,quartz diorite,porphyry granite,migmatitic granite,sye-nite,metamorphic plutonic rock,and granitic pegmatite and metagabbro(metamorphic diabase).Zir-con U-Pb dating of 15 samples from intrusive rocks was carried out in this study.The chronology framework of the Paleoproterozoic intrusive rock in the LJB was established,and the magmatism of intrusive rocks can be divided into three stages:2200 to 2110,2010 to 1937,1900 to 1820 Ma.The chronological framework supported the evolution model of subduction accretionary arc-continent colli-sion in the LJB effectively.Combined with previous geochemical work,it was a passive continental margin environment at approximately 2200 Ma,and then transformed into and active continental margin.The bimodal intrusive rocks between 2180 and 2150 Ma indicated a back-arc tension envi-ronment which lasted until approximately 2110 Ma with a large number of basic intrusive rocks.And then the back-arc basin began to contract and the magmatic activities were reduced,with only a small number of intrusive rock activities occurring at approximately 2040,2010 and 1937 Ma.After the orogenic activities,there was a post-orogenic extension stage from 1900 to 1820 Ma.Magmatic activi-ties caused by the environmental extension started to occur more frequently and subsequently resulted in the large-scale intrusive rocks in eastern Liaoning.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.92062214,41430210 and 41888101)the NSFC Regional Science Foundation(Grant No.41962012)+3 种基金the Scientific Program of Jiangxi Educational Committee(Grant No.GJJ190586)the Chinese Geological Survey projects(Grant No.DD20190003)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant No.XDB18020203)the Basic Scientific Research Foundations of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2030,J2009)。
文摘Deciphering the relationship between polyphase tectonic foliations and their associated mineral assemblages is significant in understanding the process from diagenesis to low-/medium-/high-grade metamorphism.It can provide information related to strain,metamorphic conditions and overprinting relationships and so help reveal the tectonic evolution of orogenesis.In this study,we predominately focus on the formation of foliations and their related minerals,as developed in two separate basins.First of all,two stages of axial plane cleavages(S1 and S2)were recognized in the Hongyanjing inter-arc basin,the formation of the S1 axial plane cleavage is associated with mica rotation and elongation in mudstones in the local area.The pencil structure of S2 formed during the refolding phase,the minerals in the sedimentary rocks not changing their shape and orientation.Secondly,in the Liao-Ji backarc basin,foliations include diagenetic foliation(bedding parallel foliation),tectonic S1 foliation(secondary foliation or axial plane cleavage of S0 folding)and crenulation cleavage(S2).The formation mechanism of foliation changes from mineral rotation or elongation and mineral solution transfer in S1 to crystal-plastic deformation,dynamic recrystallization and micro-folding in S2.Many index metamorphic minerals formed from low-grade to medium-grade consist of biotites,garnets,staurolite and kyanite,constituting a typical Barrovian metamorphic belt.Accordingly,a new classification of foliation is presented in this study.The foliations can be divided into continuous and disjunctive foliations,based on the existence of microlithons,detectable with the aid of a microscope.Disjunctive foliation can be further sub-divided into spaced foliation and crenulation cleavage,according to whether(or not)crenulation(micro-folding)is present.The size of the mineral grains is also significant for classification of the foliations.
文摘华北克拉通发育三条古元古代构造带,包括：东部陆块内部的胶-辽-吉带（Jiao-Liao-Ji belt）、西部陆块内部的孔兹岩带（Khondalite belt）以及两个陆块之间的中部造山带（Trans-North China Orogen）。通过二十多年的深入研究,在区域构造、变质地质、岩浆作用、地球化学、同位素年代学以及地球物理等方面积累了大量资料,并取得了一系列重要的科学进展。其中,胶-辽-吉带是华北克拉通最具代表性的一条古元古代造山/活动带,它不仅接受了古元古代巨量的陆壳物质沉积,而且经历了十分复杂的构造演化过程,并经受了多期岩浆-变质事件的改造。胶-辽-吉造山/活动带的物质组成最为丰富,以大面积分布的巨量（火山）沉积岩系为特征,在中国境内包括吉南地区的集安群和老岭群、辽东南地区的南辽河和北辽河群、胶北地区的荆山群和粉子山群,向南西则有可能穿越郯庐断裂延伸至徐州-蚌埠一带的五河群,总体呈NE向展布,延伸规模长约1000km。从巨量沉积岩系的岩石组合和空间分布特征来看,荆山群与南辽河群、集安群可以对比,而粉子山群则与北辽河群、老岭群相当。然而,由于多期/多阶段强烈构造变形作用的影响,原来各群、组中地层的上下层位及接触关系已完全破坏,目前均已呈规模不一的构造岩片形式叠置在一起,彼此之间呈断层或韧性剪切带接触。巨量变沉积岩系的源区物质主要来源于造山/活动带内古元古代花岗质岩石和两侧古老陆块的变质基底,原岩形成时代为1.95～2.15Ga左右。以往研究表明,胶-辽-吉造山/活动带变质作用的强度十分不均匀,（中-高压）麻粒岩相变质只局限于胶北的荆山群及相关岩石,而粉子山群以及辽东南的南、北辽河群和吉南的集安群、老岭群只经历了角闪岩相变质,局部甚至只达到绿片岩相变质。粉子山群、北辽河群和老岭群变
