Neoarchean subduction unveiled: Discovery of 2.5 Ga Super-Wet magmas in the Zanhuang Complex, Trans-North China Orogen

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2025-10-01 DOI:10.1016/j.precamres.2025.107931

Wen Zhang , Lilin Du , Pinghua Liu , Chonghui Yang , Wanpeng Zhou , Jianlong Wang , Qianyu Li , Guochun Zhao

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引用次数: 0

Abstract

Neoarchean lithologies of the North China Craton (NCC) provide essential insights into early continental evolution. This study investigates newly identified dioritic gneisses from the Zanhuang Complex in the central Trans-North China Orogen (TNCO) using zircon U-Pb geochronology, whole-rock geochemistry, and Nd-Hf-O isotopes. The rock types include Luzhuang tholeiitic gabbro-dioritic (2493 ± 6 Ma) and quartz dioritic (2498 ± 7 Ma) gneisses, Longmen tholeiitic garnet-bearing dioritic (2493 ± 6 Ma) and quartz dioritic (2498 ± 8 Ma) gneisses, and Shicao calc-alkaline dioritic gneisses, which are intruded by 2500 ± 18 Ma garnet-bearing anatectic granite vein. Geochemical analysis reveals relatively low MgO concentrations and Mg# values, indicating partial melting of mafic rocks. The dioritic gneisses show positive whole-rock ε_Nd(t) values (+1.9 to + 4.9) and zircon ε_Hf(t) values (+2.0 to + 10.0), suggesting a mantle-derived origin. Oxygen isotope analysis indicates zircon δ¹⁸O values ranging from 5.9 to 7.7 ‰ (average 7.0 ‰), which are higher than typical mantle zircons, indicating a metasomatized mantle source. Hygrometric calculations show 6.2–6.8 wt% H₂O in Luzhuang dioritic gneisses and 12.4–14.5 wt% H₂O in Longmen garnet-bearing varieties. The exceptionally high water content in Longmen dioritic gneisses (super-wet magmas) further supports the hypothesis of a subduction-related metasomatic process in the mantle source. These findings provide definitive evidence for Neoarchean subduction processes.

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新太古代俯冲作用揭秘：在跨华北造山带赞皇杂岩发现2.5 Ga超湿岩浆

华北克拉通的新太古代岩性为研究早期大陆演化提供了重要依据。利用锆石U-Pb年代学、全岩地球化学和Nd-Hf-O同位素等方法，对横贯华北造山带中部赞黄杂岩中新发现的闪长质片麻岩进行了研究。岩石类型包括陆庄拉斑辉长闪长岩（2493±6 Ma）和石英闪长岩（2498±7 Ma）、龙门拉斑闪长岩（2493±6 Ma）和石英闪长岩（2498±8 Ma）、石草钙碱性闪长岩（2500±18 Ma）等，均被含石榴石的浅闪长花岗岩脉侵入。地球化学分析显示MgO浓度和Mg#值相对较低，表明基性岩部分熔融。闪长质片麻岩的全岩εNd(t)值为+1.9 ~ + 4.9，锆石εHf(t)值为+2.0 ~ + 10.0，表明闪长质片麻岩为幔源。氧同位素分析表明，锆石δ18O值在5.9 ~ 7.7‰之间（平均7.0‰），高于典型的地幔锆石，为交代地幔源。湿法计算表明，芦庄闪长质片麻岩中H2O含量为6.2 ~ 6.8 wt%，龙门石榴石品种中H2O含量为12.4 ~ 14.5 wt%。龙门闪长质片麻岩（超湿岩浆）中异常高的含水量进一步支持了地幔源俯冲交代作用的假设。这些发现为新太古代俯冲过程提供了明确的证据。

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来源期刊

Precambrian Research 地学-地球科学综合

CiteScore

7.20

自引率

28.90%

发文量

325

审稿时长

12 months

期刊介绍： Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as: (1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology; (2) Geochronology and isotope and elemental geochemistry; (3) Precambrian mineral deposits; (4) Geophysical aspects of the early Earth and Precambrian terrains; (5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes. In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes. Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.