Reassessing early to mid-Neoproterozoic (∼885–720 Ma) tectonic evolution of the southwestern Jiangnan Orogen: A detrital zircon perspective

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2024-06-20 DOI:10.1016/j.precamres.2024.107482

Yong Liang , Han Zheng , Zhiyuan He , Johan De Grave , Huan Li , Zongyuan Tang , Gary G. Lash , Peixuan Kang

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Abstract

The Neoproterozoic Jiangnan Orogen (JNO) marks the consolidation of the South China Block, sparking ongoing debates on its early to mid-Neoproterozoic tectonic evolution. In this study, we have gathered detrital zircon data from the southwestern JNO, presenting new detrital zircon U-Pb ages alongside trace element data from the mid-Neoproterozoic Banxi Group and Sinian System within this region. Our objective is to illuminate the early to mid-Neoproterozoic tectonic evolution within the southwestern JNO through a comprehensive detrital zircon analysis. The obtained dating results derived from detrital zircons reveal maximum depositional ages of ∼733 Ma and ∼713 Ma for Mobin Formation (Banxi Group) and Jiangkou Formation (Sinian System) sedimentary rocks, suggesting a proximal source, possibly originating from magmatic rocks within the southwestern JNO. Within the paleo-geographic context, it is plausible that these samples were deposited within the deep-water expanse of the Nanhua Rift Basin. Trace element analysis of detrital zircons within the southwestern JNO highlights distinctive fluctuations, delineating three crucial time points (∼885 Ma, ∼835 Ma, and ∼810 Ma): the beginning of early Neoproterozoic subduction of the South China Ocean towards the Yangtze Block beneath the southwestern JNO, the subduction slab rollback, and the Nanhua rifting initiation. The discernible shifts in detrital zircon age distributions within these sedimentary rocks serve as robust validation for the proposed model and crustal reworking. We then propose that the southwestern JNO was in a lull of magmatism before ∼885 Ma, then transitioned to a convergent setting around 885–835 Ma, subsequently subduction slab rollback after ∼835 Ma. The time of final assembly of the Yangtze and Cathaysia blocks in the southwestern JNO is no later than ∼810 Ma. This transformative period (∼810–720 Ma) witnessed the development of a rift basin concurrently with the accumulation of deep-water deposits within the southwestern JNO.

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重新评估江南造山带早、中新生代（885～720Ma）构造演化：锆英石的视角

新近新生代江南造山带（JNO）标志着华南地块的整合，引发了对其早中新生代构造演化的持续争论。在这项研究中，我们收集了江南造山带西南部的碎屑锆石数据，提供了新的碎屑锆石U-Pb年龄以及该地区新元古代中期板溪组和新安系的微量元素数据。我们的目的是通过全面的碎屑锆石分析，揭示江南断裂带早、中新生代的构造演化。通过对锆英石的测定，我们发现江南断裂带西南部板溪组和江口组沉积岩的最大沉积年龄分别为733Ma和713Ma，这表明江南断裂带西南部沉积岩的近源可能来自岩浆岩。从古地理环境来看，这些样品有可能沉积在南华裂谷盆地的深水区。西南联合大断裂带内的碎屑锆石微量元素分析显示出明显的波动，划分出三个关键的时间点（885Ma∼、835Ma∼和810Ma∼）：新元古代早期华南洋开始向西南联合大断裂带下的扬子地块俯冲、俯冲板块后退和南华断裂开始。这些沉积岩中锆英石碎片年龄分布的明显变化为所提出的模型和地壳再加工提供了有力的验证。我们进而提出，江淮断裂带西南部在885Ma∼之前处于岩浆活动的低潮期，然后在885-835Ma左右过渡到汇聚环境，随后在835Ma∼之后发生俯冲板块回滚。扬子地块和国泰地块在西南JNO的最终组装时间不会晚于810Ma。在这一转变时期（810-720 Ma），断裂盆地的发展与西南联合大断裂带内深水沉积的积累同时发生。

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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.