Subduction initiation of Paleo-Pacific Ocean and final closure of Paleo-Asian Ocean: constraints from Triassic granitoids in Jiamusi Block, NE China

The process of transformation and superposition from the Paleo-Asian Ocean to the Paleo-Pacific Ocean tectonic systems have been a critical scientific issue. However, the final closure of the Paleo-Asian Ocean and the initial subduction time of the Paleo-Pacific Ocean, together with the conversion between them in Northeast China, still remain controversial. The Triassic granites in the Jiamusi Block are located in the key position of Northeast China, recording the conversion process of two tectonic domains. Through systematic geochronology and geochemical studies, it can provide important constraints for revealing the superposition and conversion mechanism of the Paleo-Asian Ocean and the Paleo-Pacific Ocean and the early subduction history of the Paleo-Pacific Ocean plate. In this study, the granites in Jiamusi Block were formed in the Early–Middle Triassic (250–245 Ma), characterized by high Si, rich alkali, poor Mg, and are obviously enriched in light rare earth elements and large ion lithophile elements, depleting in high field strength elements such as Nb, Ta, and Ti. They have typical characteristics of continental magmatic arc, deriving from partial melting of amphibolite facies and garnet amphibolite facies mafic lower crust. Combined with zircon Hf isotope results, zircon ε_Hf(t) values are −6.52 to + 9.79, and the two-stage Hf model ages are 0.6–1.7 Ga, indicating that the magma should be derived from a relative younger crustal source, and some ancient materials may be added. Moreover, based on the spatial-temporal framework and Hf isotope characteristics of magmatism in Northeast China, we believe that the Jiamusi Block belonged to an exotic block. Meanwhile, combined with geochronological and geochemical data of igneous rocks on the Jiamusi Block, we suggest that the evolution of Jiamusi Block was dominated by the Paleo-Pacific Ocean rather than Paleo-Asian Ocean during the Triassic, which means the subduction of Paleo-Pacific Ocean plate initiated at least in Early Triassic.

古亚洲洋向古太平洋构造体系的转换与叠加过程，长期以来都是核心科学议题。然而，东北地区古亚洲洋的最终闭合、古太平洋洋壳的初始俯冲时间，以及二者在该区域的转换机制，至今仍存在广泛争议。佳木斯地块的三叠纪花岗岩坐落于东北地区的关键构造位置，记录了两大构造域的转换历程。通过系统的地质年代学与地球化学研究，可为揭示古亚洲洋与古太平洋构造体系的叠加转换机制，以及古太平洋板块的早期俯冲历史提供重要约束。本研究显示，佳木斯地块的花岗岩形成于早-中三叠世（250~245 Ma），具备高硅、富碱、低镁的特征，显著富集轻稀土元素与大离子亲石元素，亏损Nb、Ta、Ti等高场强元素，具有典型的大陆岩浆弧属性，其岩浆来源于角闪岩相及石榴角闪岩相的镁铁质下地壳部分熔融。结合锆石Hf同位素分析结果，锆石ε_Hf(t)值介于-6.52至+9.79之间，两阶段Hf模式年龄为0.6~1.7 Ga，指示岩浆起源于相对年轻的地壳源区，并可能混入了部分古老地壳物质。此外，结合东北地区岩浆作用的时空格架与Hf同位素特征，本研究认为佳木斯地块属于外来地块。同时，综合佳木斯地块火成岩的年代学与地球化学数据，我们提出三叠纪时期佳木斯地块的演化主要受古太平洋构造体系而非古亚洲洋控制，这表明古太平洋板块的俯冲至少始于早三叠世。

搜集汇总

背景与挑战

背景概述

该数据集聚焦中国东北佳木斯地块的三叠纪花岗岩研究，通过地质年代学和地球化学数据，约束古太平洋洋俯冲起始时间（至少早三叠世）和古亚洲洋最终闭合的转换机制。数据集包括补充表格、图像和文档，支持结论认为佳木斯地块在二叠纪主要受古太平洋洋构造域主导，为区域构造演化提供关键证据。