The Neoproterozoic-early Paleozoic evolution of the Jiamusi Block, NE China and its East Gondwana connection: Geochemical and zircon U–Pb–Hf isotopic constraints from the Mashan Complex
The Neoproterozoic-early Paleozoic evolution of the Jiamusi Block, NE China and its East Gondwana connection: Geochemical and zircon U–Pb–Hf isotopic constraints from the Mashan Complex
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DOI：
10.1016/j.gr.2017.10.002
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发表时间：
2018-02
影响因子：
6.1
通讯作者：
Haotian Yang;W. Ge;Jun-hui Bi;Zhi-hui Wang;De-xin Tian;Yu-Chao Dong;Huijun Chen
中科院分区：
文献类型：
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作者：
Haotian Yang;W. Ge;Jun-hui Bi;Zhi-hui Wang;De-xin Tian;Yu-Chao Dong;Huijun Chen
佳木斯地块位于中亚造山带最东端，其构造亲和性和演化争议很大。本文描述了佳木斯地块马山杂岩中新发现的新元古代正长岩和早古生代花岗岩类。三个高等级正长石锆石的SIMS U-Pb测年结果显示，原岩年龄为757 ~ 751 Ma，变质年龄为530 ~ 476 Ma。4个片麻质花岗岩类锆石的LA-ICP-MS U-Pb测年确定了早古生代岩浆活动的两个阶段（530 ~ 502 Ma和490 ~ 476 Ma）。这些新资料，结合最近公布的年龄，表明佳木斯地块基底岩记录了一次重要的新元古代—早古生代岩浆活动（895 ~ 476 Ma）和变质活动（563 ~ 476 Ma），据此推断麻粒岩相变质活动可能发生在541 ~ 476 Ma之前，567 ~ 561 Ma前后。地球化学和锆石Hf同位素数据表明，ca. 752 Ma裂谷相关的片麻岩主要来自相对较低压力下枯竭软流圈地幔的热量和物质参与的幼龄地壳岩石，然后经历了古老的岩壁同化，而ca. 490-476 Ma碰撞后花岗岩类起源于古代地壳源的改造，随后经历了强烈的晶体分异。佳木斯地块与汉卡地块约755 ~ 115 Ma地质事件的对比表明，佳木斯地块与汉卡地块形成了一个连续的地壳单元。现有资料表明，该组合地块不可能直接来源于西伯利亚、华北、华南和塔里木克拉通。相反，它可能是萨扬-贝加尔湖造山带的裂谷部分，也可能来自冈瓦纳附近的位置。我们评价了嘉木斯-汉卡地块可能起源于南印度和东南极洲-澳大利亚之间的晚新元古代-寒武纪昆加造山带的一部分。约470 Ma后，它从东冈瓦纳板块脱离，向北漂移，于早侏罗世与东北松辽地块碰撞。
The Jiamusi Block is located in the easternmost Central Asian Orogenic Belt (CAOB) and its tectonic affinity and evolution is highly controversial. Here we describe newly discovered Neoproterozoic orthogneisses and early Paleozoic granitoids of the Mashan Complex from the Jiamusi Block. SIMS U-Pb dating for zircons from three high-grade orthogneisses yields protolith and metamorphic ages ranging from 757 to 751 Ma and from 530 to 476 Ma, respectively. LA-ICP-MS U-Pb dates for zircons from four gneissic granitoids define two stages of early Paleozoic magmatism (i.e., 530–502 Ma, and 490–476 Ma). These new data, together with recent published ages, indicate that the basement rocks of the Jiamusi Block record an important Neoproterozoic-early Paleozoic magmatic (ca. 895–476 Ma) and metamorphic (ca. 563–476) event, and we accordingly infer that the granulite facies metamorphism might have occurred before 541–476 Ma, and around 567–561 Ma. Geochemical and zircon Hf isotopic data suggest that the ca. 752 Ma rift-related gneisses were derived from dominantly juvenile crustal rocks with both the heat and material involvement of a depleted asthenosphere mantle at relatively low pressures, which then underwent an ancient wall-rock assimilation, whereas the ca. 490–476 Ma post-collisional granitoids originated from reworking of an ancient crustal source and subsequently experienced intensive crystal fractionation. The good correlation on the ca. 755–115 Ma geological events between the Jiamusi and Khanka blocks suggests they formed a contiguous crustal unit. The existing data indicate that this combined block cannot be directly derived from the Siberia, North China, South China, and Tarim cratons. Instead, it might be either a rifted portion of the Sayang-Baikal orogen or derived from a peri-Gondwana position. We evaluate the model that the Jiamusi-Khanka Block may have originated as part of the Late Neoproterozoic-Cambrian Kuunga orogen trapped between South India and East Antarctica-Australia. Sometime after ca. 470 Ma, it rifted away from East Gondwana and drifted northward to collide with the Songliao Block of NE China in the Early Jurassic.