Aravalli A-type granites (ca. 1.72 Ga), NW India: Petrogenesis, geodynamic evolution, and global implications for late Paleoproterozoic crustal reworking

IF 2.7 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2025-11-01 Epub Date: 2025-10-13 DOI:10.1016/j.precamres.2025.107936

Parampreet Kaur , Armin Zeh , Naveen Chaudhri , Prabhakar Dutta , Axel Gerdes

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Abstract

The geochemical and isotopic data for ca. 1.72 Ga A-type granites in the central Aravalli orogen, NW India, remain limited, hindering a detailed evaluation of their petrogenesis and tectonic setting. New results of combined zircon U-Pb-Hf isotope analyses and whole-rock geochemical data reveal that the A-type granites are characterised by high liquidus temperatures (≥850 °C), enrichment in rare earth elements and incompatible elements, and oxidised in nature. They were generated through partial melting of a silica-poor dioritic source within a post-collisional extensional setting. This A-type magmatism is synchronous with the emplacement of charnockites and granulite-facies metamorphism in the region. The coeval formation of A-type and charnockite magmas is attributed to partial melting of evolved Neoarchean crust (εHf_t = -12.5 to −5.2 and T_DM2 = 3.02 to 2.68 Ga) at moderate depth (20–25 km), triggered by upwelling of asthenospheric mantle following a slab break-off at ca. 1730 Ma. This process induced lithospheric extension and granulite-facies metamorphism in the lower crust. A global compilation of zircon Hf isotope and whole-rock Nd isotope data for late Paleoproterozoic A-type granites suggests that these rocks primarily formed by large-scale reworking of existing crustal sources, with only limited melt contributions from depleted mantle sources, thereby having a negligible impact on crustal growth over time. On the contrary, the Phanerozoic A-type granites largely represent addition of new crust.

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印度西北部Aravalli a型花岗岩（约1.72 Ga）：岩石成因、地球动力学演化及其对晚古元古代地壳改造的全球意义

印度西北部Aravalli造山带中部约1.72 Ga a型花岗岩的地球化学和同位素资料仍然有限，阻碍了对其岩石成因和构造背景的详细评价。新的锆石U-Pb-Hf同位素联合分析结果和全岩地球化学数据表明，a型花岗岩具有高液相温度（≥850℃）、稀土元素和不相容元素富集、氧化性质等特征。它们是由碰撞后伸展环境中缺乏硅质闪长岩的部分熔融形成的。这一a型岩浆活动与该区沙砾岩和麻粒岩相变质作用的侵位是同步的。a型岩浆和绿斑岩岩浆的同时形成是由1730 Ma板块断裂后软流圈地幔上涌引起的新太古代地壳（εHft = -12.5 ~ - 5.2, TDM2 = 3.02 ~ 2.68 Ga）在中深（20 ~ 25 km）的部分熔融引起的。这一过程诱发了岩石圈伸展和下地壳麻粒岩相变质作用。对晚古元古代A型花岗岩锆石Hf同位素和全岩Nd同位素数据的全球汇编表明，这些岩石主要是由现有地壳源的大规模改造形成的，只有有限的熔融贡献来自枯竭的地幔源，因此对地壳生长的影响可以忽略不计。显生宙a型花岗岩则主要代表新地壳的补充作用。

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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.