| 胶-辽-吉带构造属性与演化阶段新划分:胶北变质辉长岩的启示 |
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| 引用本文： | 王惠初,康健丽,任云伟,肖志斌,相振群,王智.胶-辽-吉带构造属性与演化阶段新划分:胶北变质辉长岩的启示[J].岩石学报,2021,37(1):185-210. |
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| 作者姓名： | 王惠初 康健丽 任云伟 肖志斌 相振群 王智 |
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| 作者单位： | 中国地质调查局天津地质调查中心, 天津 300170;中国地质调查局前寒武纪地质研究中心, 天津 300170;中国地质调查局国际矿业研究中心, 北京 100037 |
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| 基金项目： | 本文受国家重点研发计划重点专项（2016YFC0600107）、中国地质调查局地调项目（DD20160042、D20190035）和国家青年科学基金项目（4190020813）联合资助. |
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| 摘 要： | 祥山和于埠变质辉长岩是胶北地块上古元古代变质镁铁质岩石的典型代表,辉长岩侵入古元古代荆山群野头组,产有"祥山式"岩浆熔离型铁矿,成矿的专属性指示辉长岩属于层状侵入体类型,形成于大陆伸展构造背景。在祥山变质辉长岩中获得了1851±9Ma的变质年龄,在于埠变质辉长岩中获得了2052±23Ma的锆石U-Pb成岩年龄和1834±5Ma的变质年龄。~2.05Ga的岩浆结晶锆石的εHf(t)值均为正值(+1.87~+3.64),一阶段Hf模式年龄(tDM)为2292~2381Ma(平均为2327Ma),指示于埠变质辉长岩源自古元古代中期的亏损地幔。于埠变质辉长岩的成岩年龄制约了荆山群野头组的沉积上限,荆山群中至少有一部分形成于2.2~2.05Ga之间,沉积于大陆裂谷-稳定大陆边缘的构造环境。祥山和于埠变质辉长岩中有少量斜长花岗岩与之伴生,这些斜长花岗岩具有类似于大洋斜长花岗岩的岩石特征,低K、Ti、Sr,高Na、Yb,形成于低压背景;从斜长花岗岩中获得了1848±8Ma和1873±5Ma的锆石U-Pb年龄,斜长花岗岩中的锆石Th/U比值较低(0.01~0.29),具有初始熔体中结晶锆石特征。结合斜长花岗岩的地球化学特征,推测它们是辉长岩部分熔融的产物,并指示~1.87Ga已由挤压构造体制转变为伸展构造体制。综合前人研究成果,胶北地块已识别出2.18~2.15Ga、~2.10Ga、~2.05Ga的三期双峰式岩浆岩构造组合,指示2.2~2.05Ga期间总体为伸展构造背景。因此建议胶-辽-吉活动带的形成演化过程划分为两个阶段,早期为大陆裂解-稳定陆缘演化阶段(2.2~2.0Ga),沉积了巨量的陆缘碎屑岩-碳酸盐岩建造;晚期为俯冲-碰撞造山阶段(2.0~1.85Ga),胶-辽-吉活动带褶皱造山。
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| 关 键 词： | 变质辉长岩 斜长花岗岩 古元古代 构造背景 胶北地块 华北克拉通 |
| 收稿时间： | 2020/9/10 0:00:00 |
| 修稿时间： | 2020/11/29 0:00:00 |
Tectonic setting and new division of evolution stages of Jiao-Liao-Ji belt: Implications from metagabbros in Jiaobei terrane |
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| WANG HuiChu,KANG JianLi,REN YunWei,XIAO ZhiBin,XIANG ZhenQun,WANG Zhi.Tectonic setting and new division of evolution stages of Jiao-Liao-Ji belt: Implications from metagabbros in Jiaobei terrane[J].Acta Petrologica Sinica,2021,37(1):185-210. |
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| Authors: | WANG HuiChu KANG JianLi REN YunWei XIAO ZhiBin XIANG ZhenQun WANG Zhi |
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| Institution: | Tianjin Center, China Geological Survey, Tianjin 300170, China;Precambrain Geological Research Centre, China Geological Survey, Tianjin 300170, China; International Mining Research Center, China Geological Survey, Beijing 100037, China |
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| Abstract: | The Xiangshan and Yubu meta-gabbros are two typical representatives of the Paleoproterozoic metamorphic mafic rocks in the Jiaobei terrane.They intrude into the Yetou Formation of the Paleoproterozoic Jingshan Group and contain melted-separate type iron ore deposit("Xiangshan type").The specificity of mineralization indicates that the gabbros belong to the"layered intrusion type"formed in a continental extensional setting.Zircon U-Pb dating upon the collected samples yielded a magmatic age of 2052±23Ma and metamorphic ages of 1851±9Ma and 1834±5Ma for the gabbros,and metamorphic ages of 1848±8Ma and 1873±5Ma for small scale plagiogranites associated with the gabbros.The~2.05Ga magmatic zircons in Yubu meta-gabbro have positiveεHf(t)values ranging from+1.87 to+3.64 and one-stage tDM ages from 2292Ma to 2381Ma(averaged at 2327Ma),indicating that the Yubu meta-gabbro was derived from a depleted mantle source in the Middle Paleoproterozoic.The~2.05Ga emplacement age of the Yubu meta-gabbro limits the youngest deposition time of the Yetou Formation of the Jingshan Group,and is consistent with the scenario that the Jingshan Group was deposited in continental rift or stable continental margin basin environmemt.The plagioclase granites are similar to oceanic plagioclase granites in their geochemical characteristics,with low K,Ti,Sr,and high Na and Yb,indicating that they were formed in low pressure conditions,probably as a result of partial melting of gabbro when tectonic regime changed from compression to extension at~1.87Ga.Combined with previous work,three bimodal magmatic assemblages of 2.18~2.15Ga,~2.10Ga,~2.05Ga have been identified in the Jiaobei terrane,suggesting a continuous extensional process from 2.2Ga to 2.05Ga.Therefore,the formation and evolution process of the Jiao-Liao-Ji mobile belt can be divided into two stages:the early continental breakup and stable continental margin evolution stage(2.2~2.0Ga),during which a large amount of continental margin clastic rocks and carbonate rocks were deposited;and the late subduction-collision stage(2.0~1.85Ga),resulting in formation of the Jiao-Liao-Ji mobile belt orogeny. |
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| Keywords: | Meta-gabbro Plagiogranite Paleoproterozoic Tectonic Setting Jiaobei teranne North China |
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