Petrogenesis and geodynamic setting of the Wutang granites in the Tong’an-Baishuidong lithium mining district, South China: Evidence from monazite U–Pb chronology, geochemistry, and Nd–Pb isotope

IF 1.3 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Acta Geochimica Pub Date : 2025-03-27 DOI:10.1007/s11631-025-00772-z

Fushen Zhang, Xiaotian Zhang, Fangrong Zhang, Yong Zhang, Zhe Xu, Xinyu Xu, Jiayong Pan, Fei Xia, Guoqi Liu, Yu Zhou, Ying Liu, Longmin Nie, Fujun Zhong

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Abstract

The Tong’an-Baishuidong mining district (TBMD), located in the eastern section of the Jiangnan Orogen, is a newly discovered granite-type lithium mining district. Thisstudy presents new monazite U–Pb chronological, whole-rock geochemical, and Nd–Pb isotopic data to reveal the petrogenesis and geodynamic setting of the Wutang granites in the TBMD. The monazite U–Pb age of 145.8 ± 1.0 Ma indicates that the granites were emplaced at the end of the Late Jurassic. Whole-rock geochemical results demonstrate that the Wutang granites are enriched in SiO₂ (72.80–73.40 wt%) but depleted in CaO (0.44–0.90 wt%) and MgO+TiO₂+TFeO (1.79–2.05 wt%). These granites exhibit negative Eu anomalies (δEu = 0.3−0.4) and high aluminum saturation indexes (A/CNK = 1.2−1.6), differentiation indexes (DI = 90–92), and Rb/Sr ratios (4.7–8.1). They also have moderate Ba contents (239–278 ppm) and low Sr contents (52.7–82.0 ppm) as well as low Nb/Ta (2.2–5.3) and Zr/Hf (21.3–31.5) ratios. All these indicate that they are highly fractionated granites. Additionally, these granites contain 5–10 wt% muscovite but no hornblende, with calculated corundum contents of 2.3–5.5 wt%. They have low high-field strength element (HFSE) contents (Zr + Nb + Ce + Y = 182–202 ppm) and zircon saturation temperatures (700–770 °C), with Th and Y negatively linked with Rb. These petrographic and geochemical features further reveal that the Wutang granites belong to highly fractionated S-type granites. The ε_Nd(t) values of these granites range from −9.03 to −8.23, corresponding to two-stage model ages (T_DM2) of 1488–1553 Ma. The initial Pb isotope ratios are: (²⁰⁶Pb/²⁰⁴Pb)_i = 18.38–18.55, (²⁰⁷Pb/²⁰⁴Pb)_i = 15.67–15.68, and (²⁰⁸Pb/²⁰⁴Pb)_i = 38.62–38.67. These Nd–Pb isotopic results demonstrate that the parental magma originated from the partial melting of ancient crustal materials. In the meantime, the TBMD in the eastern section of the Jiangnan Orogen was in a compression-extension transitional setting associated with the episodic subduction of the Paleo-Pacific Plate.

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通安-白水洞锂矿区五塘花岗岩成因及地球动力学背景：来自独独居石U-Pb年代学、地球化学和Nd-Pb同位素的证据

通安-白水洞矿区位于江南造山带东段，是一个新发现的花岗岩型锂矿区。本文利用新的单独居岩U-Pb年代学、全岩地球化学和Nd-Pb同位素资料，揭示了武唐花岗岩的岩石成因和地球动力学背景。单独居石的U-Pb年龄为145.8±1.0 Ma，表明花岗岩形成于晚侏罗世末期。全岩地球化学结果表明，武唐花岗岩富SiO2 (72.80 ~ 73.40 wt%)，贫CaO （0.44 ~ 0.90 wt%）和MgO+TiO2+TFeO （1.79 ~ 2.05 wt%）。这些花岗岩具有负Eu异常（δEu = 0.3 ~ 0.4）、高铝饱和度指数（A/CNK = 1.2 ~ 1.6）、分异指数（DI = 90 ~ 92）和Rb/Sr比值（4.7 ~ 8.1）。它们的Ba含量适中（239 ~ 278 ppm）， Sr含量较低（52.7 ~ 82.0 ppm）， Nb/Ta（2.2 ~ 5.3）和Zr/Hf（21.3 ~ 31.5）比较低。这些都表明它们是高度分异的花岗岩。此外，这些花岗岩含有5-10 wt%的白云母，而不含角闪石，计算出刚玉含量为2.3-5.5 wt%。它们具有较低的高场强元素（HFSE）含量（Zr + Nb + Ce + Y = 182 ~ 202 ppm）和锆石饱和温度（700 ~ 770℃），Th和Y与Rb呈负相关。这些岩石学和地球化学特征进一步表明，武塘花岗岩属于高分异s型花岗岩。这些花岗岩的εNd(t)值在−9.03 ~−8.23之间，对应于1488 ~ 1553 Ma的两阶段模式年龄（TDM2）。初始Pb同位素比值为：（206Pb/204Pb）i = 18.38 ~ 18.55, (207Pb/204Pb)i = 15.67 ~ 15.68, (208Pb/204Pb)i = 38.62 ~ 38.67。这些Nd-Pb同位素结果表明母岩浆起源于古地壳物质的部分熔融。与此同时，江南造山带东段的TBMD处于古太平洋板块幕式俯冲的挤压—伸展过渡背景。

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来源期刊

Acta Geochimica GEOCHEMISTRY & GEOPHYSICS-

CiteScore

2.80

自引率

6.20%

发文量

1134

期刊介绍： Acta Geochimica serves as the international forum for essential research on geochemistry, the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth‘s crust, its oceans and the entire Solar System, as well as a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. The journal focuses on, but is not limited to the following aspects: • Cosmochemistry • Mantle Geochemistry • Ore-deposit Geochemistry • Organic Geochemistry • Environmental Geochemistry • Computational Geochemistry • Isotope Geochemistry • NanoGeochemistry All research articles published in this journal have undergone rigorous peer review. In addition to original research articles, Acta Geochimica publishes reviews and short communications, aiming to rapidly disseminate the research results of timely interest, and comprehensive reviews of emerging topics in all the areas of geochemistry.