2024年8月28日出版的《地球化学学报》杂志发表了西南石油大学朱玉娣团队的最新成果，研究报道了青藏高原东部江浪穹隆晚三叠世正长岩及同期后生铜矿化。

江浪穹隆具有完整的构造地层单位，包含一套高品质层状铜矿床。然而，该穹隆的形成机制和同矿化的成因模式仍然存在争议。这些问题的解决取决于地核中是否存在岩浆侵入。

研究人员报告了一个新发现的正长岩体的整体地球化学、锆石U-Pb数据以及黄铜矿Re-Os测年结果。研究探讨了江浪穹窿的成因、层状铜矿床的成因模式及正长岩内部稀有金属的成矿潜力。正长岩样品的侵位年龄为207.1±2.0Ma，与松潘-甘孜造山带碰撞后伸展相吻合。正长岩的平均高(Zr+Nb+Ce+Y)浓度为512ppm，10000×Ga/Al比值为3.97，结晶温度为827℃，低Mg#值为1.73；它们符合A型花岗岩的定义和地壳起源。

黄铜矿分离物的Re-Os等时线年龄为207.1±5.3Ma，明显晚于其含矿岩(Liwu群，ca.553Ma)。新的年龄测定，连同先前的黄铜矿Re-Os等时线年龄约为151.1Ma，硫化物硫同位素(δ³⁴SV-CDT=8.7‰-5.6‰)及其卤化物硼同位素(δ¹¹B=-15.47‰至-5.91‰)资料，证实了与岩浆-热液流体有关的多期后成铜矿化。与ca.209-207Ma区域的富质花岗岩类相比，所研究的正长岩侵入体显示，未演化和贫瘠的亲和性以及稀有金属成矿潜力可忽略不计。结合江浪穹窿核心残余重力低异常，表明存在一个大型的深部花岗质基底，研究人员更倾向于认为该穹窿的性质为岩浆隆升所致的热穹窿。

附：英文原文

Title: First discovery of the Late Triassic syenite and coeval epigenetic Cu mineralization in the Jianglang Dome, eastern Tibetan Plateau, China

Author: Dai, Yanpei, Zhu, Yudi, Xiu, Di, Zhang, Huihua, Liang, Shengxian, Li, Tongzhu, Zhou, Qing

Issue&Volume: 2024-08-28

Abstract: The Jianglang Dome has integral tectonostratigraphic units and contains a suite of high-grade stratiform Cu deposits. However, the formation mechanism of this dome and genetic model of Cu mineralization remain a matter of debate. The resolution of these problems hinges on the presence of magmatic intrusions in the core. Here, we report bulk geochemical and zircon U-Pb data of a newly discovered syenite intrusion as well as chalcopyrite Re-Os dating results. We aim to explore genesis of the Jianglang Dome, genetic model of the stratiform Cu deposits, and rare metal mineralization potential of the syenite intrusion. The dated syenite sample yields an emplacement age of 207.1±2.0 Ma, which matches post-collisional extension in the Songpan-Ganze Orogen. The syenite rocks have average high (Zr+Nb+Ce+Y) concentrations of 512 ppm, 10000×Ga/Al ratios of 3.97, and crystallization temperatures of 827 °C, together with low Mg# values of 1.73; they fit the A-type granitoid definition and a crustal origin. Chalcopyrite separates yield a Re-Os isochron age of 207.1±5.3 Ma, which markedly postdates the formation age of their ore-hosting rocks (the Liwu Group, ca. 553 Ma). Our new age determination, together with previous chalcopyrite Re–Os isochron age of ca. 151.1 Ma and sulfide sulfur isotope (δ³⁴SV-CDT=8.7‰–5.6‰) and tourmaline boron isotope (δ¹¹B=-15.47‰ to -5.91‰) data, confirms multistage epigenetic Cu mineralization related to magmatic-hydrothermal fluids. Compared with regional ca. 209–207 Ma fertile granitoids, the studied syenite intrusion shows unevolved and barren affinities and negligible rare metal mineralization potential. Combined with residual gravity low anomalies in the core of the Jianglang Dome, which suggest a large deep-seated granitic batholith, we prefer thermal doming resulting from magma-induced uplift for the nature of this dome.

DOI: 10.1007/s11631-024-00732-z

Source: https://link.springer.com/article/10.1007/s11631-024-00732-z