3.1 Ga左右全球岩浆事件和地壳演化
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1.深层油气全国重点实验室(中国石油大学(华东));2.青岛海洋科技中心海洋矿产资源评价与探测技术功能实验室;3.崂山国家实验室

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国家自然科学(编号:42272225)、崂山实验室科技创新项目(编号:LSKJ202203401)、山东省自然科学基金面上项目(编号:ZR2021MD083)、中央高校基本科研业务费专项(编号:23CX09004A)


~3.1 Ga Global magmatic events and crustal evolution
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1.State Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China);2.Laboratory for Marine Mineral Resources,Qingdao Marine Science and Technology Center;3.Laoshan National Laboratory

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    摘要:

    全球克拉通90%的陆壳可能是在太古宙形成,集中在3.5-3.1Ga、2.8-2.7Ga、2.6-2.5Ga三个阶段,2.8~2.7Ga和晚期2.6~2.5Ga时期的岩石保留较多,地壳增生与改造机制研究较多,受样品稀少限制,3.0 Ga之前的岩浆事件与陆壳形成演化研究相对薄弱,早前寒武纪岩浆事件与地壳增生方式仍存在争议。本文系统总结了全球中太古代(主要为3.2-3.0Ga期间)岩石的锆石年龄、岩石类型、全岩地球化学和锆石Lu-Hf-O同位素特征。主要认识包括:(1)3.2-3.0Ga时期岩石在全球各大洲均有分布,现今主要集中在北半球,而南半球的数量相对较少;(2)岩石的锆石年龄峰值集中在约3.05Ga和约3.15Ga两个时期;(3)岩石的主要岩性为英云闪长岩和奥长花岗岩,具有过铝质的特征,不同地区呈现出不同的岩石组合,展现出一定的地区独特性;(4)不同地区岩石锆石的εHf(t)值表现出明显差异,反映了岩石起源和演化历史的差异性。大部分锆石的δ18O值与地幔熔体处于平衡状态,也有部分锆石的δ18O值较高,可达+8.93‰,暗示岩石源区经历了一定的低温蚀变或地壳物质的混染;(5)岩石呈现轻稀土元素富集、重稀土元素亏损的右倾模式,铕元素异常明显。整体上Th、U、K、Pb等元素相对富集,而Nb、Ta、P、Sm、Ti等元素相对亏损。综合研究表明:(1)3.1Ga左右TTG岩石可能由经历低温蚀变的玄武质岩石部分熔融形成。Hf同位素特征显示,该时期玄武质岩石多数为3.3Ga左右时期由轻度亏损的地幔部分熔融形成。(2)中太古代早期(主要为3.2-3.0Ga期间)发生了一次全球性质的岩浆活动和地壳增长事件,峰值期在约3.05Ga和约3.15Ga。(3)类似于现代板块运动的构造体制在中太古代已经启动。

    Abstract:

    Objectives: During the Archean, approximately 90% of the global craton's crust may have formed, particularly during the 3.5~3.1 Ga, 2.8~2.7 Ga, and 2.6~2.5 Ga. More rocks are preserved from the 2.8~2.7 Ga and late 2.6~2.5 Ga periods. While the mechanisms of crustal accretion and remodeling are frequently investigated, research is limited by the scarcity of samples, resulting in relatively weak studies on magmatic events and crustal formation prior to 3.0 Ga. Furthermore, the understanding of earlier Preambrian magmatic events and crustal accretion remains controversial. Methods: Building upon previous research, this study summarizes and compares zircon ages, rock types, whole-rock geochemistry, and zircon Lu-Hf-O isotope signatures of global Mesoproterozoic rocks, primarily from the 3.2-3.0 Ga period, in order to concluding the global magmatic events and crustal evolution patterns around 3.1 Ga. Results: Rocks from the 3.2-3.0 Ga period are found across all continents, with a predominant concentration in the Northern Hemisphere, while the Southern Hemisphere exhibits a relatively smaller number in present. The peak zircon ages of these rocks are concentrated around 3.05 Ga and 3.15 Ga. The main lithologies include stromatolitic and peraluminous aeolian granite.The primary lithologies of the rocks consist of angstromatolite and aeolian granite with peraluminous characteristics. Different regions exhibit distinct rock assemblages, and the εHf(t) values of zircons from these regions demonstrate significant variations, reflecting differences in the origin and evolutionary history of the rocks. Most zircons have δ18O values in equilibrium with mantle melt; however, some zircons exhibit higher δ18O values, reaching +8.93‰, suggesting that the rock source areas underwent low-temperature alteration or mixing with crustal materials. The rocks display a right-tilted pattern characterized by an enrichment of light rare earth elements and a deficit of heavy rare earth elements, with pronounced europium anomalies. Overall, elements such as Th, U, K, and Pb are relatively enriched, whereas elements like Nb, Ta, P, Sm, and Ti are comparatively deficient. Conclusions: The ~3.1 Ga rocks likely formed through partial melting of a basaltic source region that experienced low-temperature alteration. This source region originated from partial melting of a mildly deficient mantle around ~3.3 Ga. A global event of magmatism and crustal growth occurred during the early Mesoarchean (primarily between 3.2 and 3.0 Ga), with peaks at approximately 3.05 Ga and 3.15 Ga. Furthermore, tectonic regimes akin to modern plate motions began to emerge in certain areas during the Mesoarchean.

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  • 收稿日期:2024-10-21
  • 最后修改日期:2024-12-16
  • 录用日期:2024-12-23
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