胶-辽-吉造山带辽河群含钴层位里尔峪组变火成岩成因机制及其对复杂构造演化过程的制约  

Genetic mechanism of meta-igneous rocks in the Co-bearing Li'eryu Formation,Liaohe Group:Constraints on the tectonic evolution of the Jiao-Liao-Ji Paleoproterozoic orogenic belt

作　　者：李同宇 刘福来[1] 王舫[1] 廉涛[2] 邓文婷[2] 孙莉[2] LI TongYu;LIU FuLai;WANG Fang;LIAN Tao;DENG WenTing;SUN Li(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Liaoning Province Seventh Geological Brigade Co.,Ltd.,Dandong 118003,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]辽宁省第七地质大队有限责任公司,丹东118003

出　　处：《岩石学报》2024年第10期3055-3089,共35页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(92062214);国家重点研发计划项目(2022YFC2903502);中国地质调查项目(DD20242528)联合资助.

摘　　要：辽河群里尔峪组变基性岩与变长英质粒状岩石记录了胶-辽-吉古元古代造山带复杂演化过程的重要信息。该组不仅是辽东钴富集成矿的关键层位,也是深入探讨胶-辽-吉造山带古元古代起始构造背景及其演化过程的关键研究对象。本文通过野外地质调查、岩相学、全岩地球化学、锆石年代学以及Lu-Hf同位素的综合研究,对里尔峪组中变基性岩与变长英质粒状岩石的原岩属性、成因机制、年代格架及构造背景进行了深入研究,结合胶-辽-吉带古元古代的构造演化过程及其与Co元素的初始来源的内在成因关系进行了初步讨论。里尔峪组变基性岩岩石主要由斜长角闪岩与变角闪石岩组成,变长英质粒状岩石包括浅粒岩和变粒岩。野外观察发现大量变基性岩侵入到变长英质粒状岩石中。锆石U-Pb定年结果表明,变基性岩的原岩形成时代为2160~2130Ma,变长英质粒状岩石原岩的形成时代为2200~2160Ma,两者共同经历了1950~1850Ma古元古代变质事件的改造。根据地球化学特征,变基性岩可分为三种类型:第一类斜长角闪岩属于拉斑玄武岩系列,轻微富集LREE,类似E-MORB特征,Nb、Ta、Ti、Zr和Hf轻微亏损,暗示有限的流体交代和地壳混染,变质锆石ε_(Hf)(t)值为-2.3~5.9,t DM1集中在2200~2100Ma,表明其原岩来源于亏损的软流圈地幔,指示古元古代新生地壳生长事件;第二类斜长角闪岩属于钙碱性系列,具有右倾的稀土元素配分曲线,Nb、Ta和Ti元素明显亏损,Zr、Hf正异常,表明其原始岩浆在离开源区后可能经历了地壳混染;第三类变角闪石岩属于超基性岩,REE总量相对偏高,LREE相对富集,Nb、Ta、Ti、Zr和Hf明显亏损,显示出有限的地壳混染和大量流体交代,岩浆锆石ε_(Hf)(t)值为-2.3~6.7,t DM1集中在2500~2200Ma;变质锆石ε_(Hf)(t)值为-5.9~-0.4,t DM1集中在2500~2300Ma,其原岩应来源于富集的岩石圈地幔。在变长英质粒状岩�The Li'eryu Formation of the Liaohe Group,including meta-basic rocks and meta-felsic rocks,preserves significant information related to the thermodynamic and geochemical evolution of the Jiao-Liao-Ji orogenic belt.These rocks not only serve as critical stratigraphic units for cobalt enrichment in the Jiao-Liaodong region,but also constitute essential elements for unraveling the Paleoproterozoic tectonic background and evolutionary processes of the Jiao-Liao-Ji orogenic belt.In this study,a comprehensive approach,involving detailed field investigations,petrology,zircon geochronology and Lu-Hf isotope analyses,and whole-rock geochemistry,was employed to thoroughly investigate the protolith characteristics,formation mechanisms,geochronological framework and tectonic background of the meta-basic rocks and meta-felsic rocks in the Li'eryu Formation.Moreover,a preliminary discussion was carried out to establish an intrinsic relationship between the Paleoproterozoic tectonic evolution of the Jiao-Liao-Ji orogenic belt and the initial sources of cobalt.The Li'eryu Formation is primarily composed of meta-basic rocks,mainly consisting of amphibolites and meta-hornblende rocks,while the meta-felsic rocks include leptite and leptynite.Field observations reveal that mafic rocks intruded into the felsic plutonic rocks within the study area.Zircon U-Pb dating results indicate that the protolith formation age of the meta-basic rocks ranges within 2160~2130Ma,while the meta-felsic rocks were formed in 2200~2160Ma.These rocks underwent a Paleoproterozoic metamorphic event during the 1950~1850Ma.Based on the geochemical characteristics,the meta-basic rocks can generally be divided into three types,and each of them has different features as follows:(1)The first type of amphibolites falls within the tholeiitic series and exhibits slight enrichment in LREE,resembling E-MORB features;and they notably display slight depletions in Nb,Ta,Ti,Zr and Hf,suggesting limited fluid alteration and crustal contamination;furthermore,the metamorphic

关 键 词：胶-辽-吉造山带 里尔峪组 变基性岩和变长英质粒状岩石 年代学 地球化学 弧后盆地 

分 类 号：P588.34[天文地球—岩石学] P597.3[天文地球—地质学] P618.62