U-Pb zircon-monazite-apatite geochronology and zircon Hf isotope composition of syenite-clinopyroxenite suite from Nayagarh (Odisha) of the Eastern Ghats Province

IF 2.7 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2026-06-01 Epub Date: 2026-03-02 DOI:10.1016/j.precamres.2026.108065

Divyajyoti D. Rana , Dewashish Upadhyay , Jayanta Kumar Nanda , Mousumi Bhattacharjee

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Abstract

A clinopyroxene-bearing syenite suite, hosted in charnockitic orthogneiss in the Nayagarh region of the Eastern Ghats Province, records multiple magmatic and metamorphic events. This study combines petrography, mineral chemistry, U–Pb geochronology of zircon, monazite, and apatite, and zircon Hf isotopes to constrain its petrogenesis and tectonic evolution. The syenite comprises mainly K-feldspar with subordinate clinopyroxene and accessories like zircon, allanite, thorite, monazite, titanite, and apatite. Apatite veins cutting syenite–pyroxenite bodies are light rare earth element-enriched. Zircon grains feature magmatic cores and metamorphic overgrowths. Magmatic domains yield a concordant U–Pb age of 979 ± 6 Ma (2σ, n = 28; MSWD = 2.0), marking syenite intrusion. A xenocrystic zircon at 1744 ± 63 Ma indicates older crustal inheritance. Metamorphic overgrowths date to 792 ± 9 Ma (2σ, n = 9; MSWD = 0.060) and 541 ± 10 Ma (2σ, n = 2; MSWD = 0.000117). Monazite gives a concordant age of 458 ± 8 Ma (2σ, n = 5; MSWD = 0.27), while apatite yields a Tera–Wasserburg intercept of 410 ± 15 Ma (2σ; MSWD = 10). Zircon εHf(t) values range from –12.1 to + 4.7, signaling mixed juvenile and crustal sources, with depleted mantle model ages of 2.75–2.90 Ga for crustal extraction. The ∼ 979 Ma syenite emplacement aligns with Chilka Lake anorthosite and widespread anorthosite–charnockite–granitoid magmatism in the Eastern Ghats Belt, tying to Grenville-age post-orogenic extension after Eastern Ghats accretion to the Indian Shield and East Antarctica during Rodinia assembly. The ∼ 792 Ma event reflects high-grade metamorphism and decompression in Chilka Lake, linked to Rodinia breakup and East Antarctic–Indian separation. The ∼ 541 Ma zircons correlate with Kuunga orogeny, while 458 Ma monazite and 410 Ma apatite record hydrothermal alterations from later thermal pulses.

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东高塞省Nayagarh （Odisha）正长-斜辉石岩套U-Pb锆石-单氮石-磷灰石年代学及锆石Hf同位素组成

东高止省Nayagarh地区含斜辉石正长岩套产于绿质正长岩中，记录了多次岩浆和变质事件。结合锆石、独居石和磷灰石的岩石学、矿物化学、U-Pb年代学和锆石Hf同位素对其岩石成因和构造演化进行了研究。正长岩以钾长石为主，辅之有斜辉石，辅之有锆石、allanite、thorite、独居石、钛矿、磷灰石等。切入正长辉石岩体的磷灰石脉富含轻稀土元素。锆石颗粒具有岩浆岩心和变质生长体特征。岩浆域中U-Pb年龄为979±6 Ma (2σ, n = 28, MSWD = 2.0)，显示正长岩侵入。1744±63 Ma的异晶锆石表明更古老的地壳遗传。变质过度生长为792±9 Ma （2σ, n = 9, MSWD = 0.060）和541±10 Ma （2σ, n = 2, MSWD = 0.000117）。独居石的年龄为458±8 Ma (2σ, n = 5, MSWD = 0.27)，磷灰石的Tera-Wasserburg截距为410±15 Ma （2σ, MSWD = 10）。锆石εHf(t)值介于-12.1 ~ + 4.7之间，表明锆石源与地壳源混合，地壳提取的贫地幔模型年龄为2.75 ~ 2.90 Ga。~ 979 Ma正长岩位与奇尔卡湖斜长岩和东高止带广泛的斜长岩-绿绿岩-花岗质岩浆作用一致，与Rodinia组装期间东高止向印度盾和东南极洲增生后的grenville时代造山后伸展有关。~ 792 Ma事件反映了Chilka湖的高变质和减压作用，与Rodinia分裂和东南极洲-印度分离有关。~ 541 Ma的锆石与昆加造山运动有关，而458 Ma的独居石和410 Ma的磷灰石则记录了后期热脉冲的热液变化。

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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.