近日，东华理工大学张勇团队研究了华南同安-白水洞锂矿区五塘花岗岩的成因及地球动力学背景。相关论文于2025年3月27日发表在《地球化学学报》上。

同安-白水洞矿区位于江南造山带东段，是新发现的花岗岩型锂矿区。研究组提供了新的独居石U-Pb年代学、全岩地球化学和Nd-Pb同位素数据，以揭示TBMD中五塘花岗岩的岩石成因和地球动力学背景。独居石的U-Pb年龄为145.8±1.0 Ma，表明花岗岩是在晚侏罗世末侵位的。全岩地球化学结果表明，武当花岗岩富含SiO₂（72.80-73.40 wt%），但贫CaO（0.44-0.90 wt%）和MgO+TTiO₂+TFeO（1.79-2.05 wt%）。

这些花岗岩表现出负Eu异常（δEu=0.3-0.4）和高铝饱和度指数（A/CNK） = 1.2−1.6），分化指数（DI=90-92），Rb/Sr比值（4.7-8.1）。它们还具有适中的Ba含量（239-278 ppm）和较低的Sr含量（52.7-82.0 ppm），以及较低的Nb/Ta（2.2-5.3）和Zr/Hf（21.3-31.5）比。所有这些都表明它们是高度分馏的花岗岩。此外，这些花岗岩含有5-10 wt%的白云母，但不含角闪石，计算出的刚玉含量为2.3-5.5 wt%。

它们具有低的高场强元素（HFSE）含量（Zr+Nb+Ce+Y=182-202ppm）和锆石饱和温度（700-770°C），Th和Y与Rb呈负相关。这些岩相和地球化学特征进一步表明，五塘花岗岩属于高度分馏的S型花岗岩。这些花岗岩的ε_Nd（t）值范围为-9.03至-8.23，对应于1488-1553 Ma的两阶段模型年龄（T_DM2）。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，母岩浆起源于古代地壳物质的部分熔融。与此同时，江南造山带东段的TBMD处于与古太平洋板块幕式俯冲相关的挤压-伸展过渡环境中。

附：英文原文

Title: 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

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

Issue&Volume: 2025-03-27

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=0.30.4) and high aluminum saturation indexes (A/CNK=1.21.6), 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 εNd(t) values of these granites range from 9.03 to 8.23, corresponding to two-stage model ages (TDM2) 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.

DOI: 10.1007/s11631-025-00772-z

Source: https://link.springer.com/article/10.1007/s11631-025-00772-z