Middle Neoproterozoic (ca. 715 Ma) slab window along the Yangtze northern margin: Constrained from meta-mafic igneous records

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Precambrian Research Pub Date : 2024-11-26 DOI:10.1016/j.precamres.2024.107630

Feifei Zhang , Mingxia Wang , Peter A. Cawood , Yunpeng Dong , Yifan Wang , Bo Hui , Shuai He , Hongsen Gao

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Abstract

We constrain the Neoproterozoic tectonic pattern and subduction termination records of the Yangtze Block through new geochronological, geochemical and Sr-Nd-Pb-Hf isotopic data for the metabasites of the Wudang Group in the South Qinling Belt. Our data show that these meta-igneous rocks formed at ca. 715 Ma and can be compositionally classified into five groups: arc- and MORB-like, high-Nb and Nb-enriched metabasite, and high-Mg andesite. Their ε_Nd(t) values range from + 5.4 to −0.4, (²⁰⁶Pb/²⁰⁴Pb)_i from 16.53 to 17.47, (²⁰⁷Pb/²⁰⁴Pb)_i from 15.34 to 15.49, (²⁰⁸Pb/²⁰⁴Pb)_i from 36.54 to 37.46 with Δ8/4 = +65 ∼ +173 and Δ 7/4 = +4.5 ∼ +10.5, respectively. Their source was the convergent plate margin mantle wedge, modified by subduction-related component or interacting with the OIB-type asthenospheric mantle. Together with available data, the Wudang Group in the South Qinling Belt is characterized by the Neoproterozoic volcano-sedimentary rocks, with the volcanic rocks are dominated by the ca. 850–780 Ma mafic, ca. 780–730 Ma felsic and ca. 720–710 Ma mafic rocks. The Wudang Group is overlain by the ca. 700–630 Ma rift-related Yaolinghe Group with the intervening angular unconformity constrained to an age of ca. 710–700 Ma. Based on regional data from the northern margin of the Yangtze Block, we propose a long-lived Neoproterozoic (∼890–710 Ma) a north facing arc-trench system with south-directed subduction ongoing until ca. 710 Ma. This subduction termination could reflect the development of a tear-induced slab window model in the South Qinling Belt.

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长江北缘新近纪中期（约715Ma）板块窗口：元火成岩记录的约束

我们通过对南秦岭带武当山组偏绿岩新的地质年代、地球化学和Sr-Nd-Pb-Hf同位素数据，对长江地块的新新生代构造模式和俯冲终止记录进行了约束。我们的数据显示，这些元火成岩形成于约我们的数据表明，这些元火成岩形成于约715 Ma，从成分上可分为五类：弧样和MORB样、高Nb和Nb富集的偏闪长岩以及高镁安山岩。它们的εNd(t)值分别为+ 5.4 ∼ -0.4，(206Pb/204Pb)i为16.53 ∼ 17.47，(207Pb/204Pb)i为15.34 ∼ 15.49，(208Pb/204Pb)i为36.54 ∼ 37.46，Δ8/4 = +65 ∼ +173 和Δ7/4 = +4.5 ∼ +10.5。它们的来源是汇聚的板块边缘地幔楔，经过俯冲相关成分的改变或与 OIB 型星体层地幔的相互作用。结合现有资料，南秦岭地块武当山组以新近新生代火山-沉积岩为主，火山岩以约850-780Ma的岩浆岩为主。南秦岭地块的武当山群以新近纪火山-沉积岩为特征，火山岩以约850-780Ma黑云母岩、约780-730Ma长英岩和约720-710Ma黑云母岩为主。武当组上覆约700-630 Ma与裂谷有关的岩层。武当组上覆有约700-630 Ma与裂谷有关的窑岭河组，其间的角状不整合岩的年龄约为710-700 Ma。根据长江地块北缘的区域数据，我们提出了一个长寿的新元古代（890-710 Ma）北向弧沟系统，其南向俯冲一直持续到约710 Ma。这一俯冲终止可能反映了南秦岭地块撕裂诱发板块窗口模式的发展。

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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.