滇西北浪都夕卡岩矿床致矿岩体的岩石地球化学、年代学、Sr-Nd-Pb同位素组成及其地质意义  

Petrogeochemistry,chronology,Sr-Nd-Pb isotopic compositions,and geological significance of the ore-causative intrusion in the Langdu skarn deposit,northwest Yunnan

作　　者：莫雷 沈啟武 陈喜连 吴练荣 张传昱 董桥峰 苏肖宇 施宝生 余海军 冷成彪 MO Lei;SHEN Qiwu;CHEN Xilian;WU Lianrong;ZHANG Chuanyu;DONG Qiaofeng;SU Xiaoyu;SHI Baosheng;YU Haijun;LENG Chengbiao(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Yunnan Diqing Nonferrous Metal Co.,Ltd.,Shangri-La 674400,China;Yunnan Geological Survey,Kunming 650216,China;Yunnan Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Kunming 650051,China;Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,MNR,Kunming 650051,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]云南迪庆有色金属有限责任公司,云南香格里拉674400 [3]云南省地质调查院,云南昆明650216 [4]云南省三江成矿作用及资源勘查利用重点实验室,云南昆明650051 [5]自然资源部三江成矿作用及资源勘查利用重点实验室,云南昆明650051

出　　处：《沉积与特提斯地质》2024年第2期421-436,共16页Sedimentary Geology and Tethyan Geology

基　　金：第二次青藏高原综合科学考察研究(2021QZKK0301);国家自然科学基金项目(42102098,42173026);云南迪庆有色金属责任公司科研项目(DQYS-SCB-08-(2022)031);东华理工大学研究生创新基金(YC2023-S550)。

摘　　要：滇西北浪都侵入岩体位于义敦岛弧南段的中甸弧,在空间上属浪都夕卡岩型铜矿床的致矿岩体。本文以浪都致矿岩体中石英二长斑岩为对象,对其开展了锆石SIMS(二次离子质谱)U-Pb定年、岩石地球化学和Sr-Nd-Pb同位素研究。锆石U-Pb定年结果显示浪都石英二长斑岩的成岩年龄为219.2±1.8 Ma(2σ,MSWD=1.3,n=13),与中甸弧中晚三叠世侵入岩体成岩年龄基本一致。浪都石英二长斑岩具有中等SiO2含量(w(SiO_(2))为60.42%~66.44%),高Al_(2)O_(3)(w(Al2O3)为14.56%~16%)和高K2O(w(K_(2)O)为3.49%~4.49%)含量,以富集LREE和Rb、Ba、Sr等大离子亲石元素,相对亏损HREE和Ta、Nb、Ti等高场强元素为特征,在化学成分上属于高钾钙碱性系列。此外,浪都石英二长斑岩的87Sr/86Sr初始值为0.7054~0.7061,εNd(t)值为-3.5~-2.5,且所有样品在Pb同位素构造模式图上均落在造山带演化线附近。结合浪都石英二长斑岩的成岩时代、岩石化学和同位素特征,本文认为浪都致矿岩体形成于晚三叠世甘孜-理塘洋壳西向俯冲增生的构造背景,是交代地幔部分熔融形成的熔体在上升过程中受到下地壳物质混染,并经历分离结晶作用形成的产物。浪都石英二长斑岩的高Sr/Y比值和高V/Sc比值,指示岩浆具有高含量H2O和较高的氧逸度,是该区斑岩-夕卡岩铜矿床形成的关键。The Langdu intrusion in northwestern Yunnan is located in the Zhongdian arc of the southern Yidun terrane and it belongs to the ore-causative intrusion of Langdu skarn-type copper deposit,spatially.This study focuses on the quartz-diorite porphyry within the Langdu ore-bearing intrusion and investigates its zircon SIMS U-Pb dating,rock geochemistry,and Sr-Nd-Pb isotopic composition.The zircon U-Pb dating results reveal a crystallization age of 219.2±1.8 Ma(2σ,MSWD=1.3,n=13)for the Langdu quartz-diorite porphyry,which is consistent with the late Triassic intrusive rocks in the Zhongdian arc.The Langdu quartzdiorite porphyry exhibits medium SiO_(2)(60.42%–66.44%),high Al_(2)O_(3)(14.56%–16%),and high K_(2)O(3.49%–4.49%)contents.It is characterized by enrichment of LREE and large ion lithophile elements such as Rb,Ba,and Sr,and relative depletion of HREE and high field strength elements such as Ta,Nb,and Ti,belonging to the high-K calc-alkaline series.Additionally,the initial 87Sr/86Sr ratios of the Langdu quartz-diorite porphyry range from 0.7054 to 0.7061,andεNd(t)values range from-3.5 to-2.5.All samples are plotted near the orogenic evolution line on the Pb isotope evolutionary diagram.Combining the petrological,geochemical,and isotopic characteristics of the Langdu quartz-diorite porphyry,this study suggests that the Langdu ore-bearing intrusion formed in relation to the westward subduction and accretion of late Triassic Garez-Litang oceanic crust.It was a product of partial melting of the metasomatized mantle,mixed with lower crustal material during its ascent,and experienced intense fractional crystallization.The high Sr/Y and high V/Sc ratios of the Langdu quartz-diorite porphyry indicate the characteristics of high-water content and relatively high oxygen fugacity in the magma,which are probably key factors controlling the formation of the porphyry-skarn copper deposit in this region.

关 键 词：浪都 致矿岩体 岩石地球化学 锆石U-PB年龄 SR-ND-PB同位素 

分 类 号：P618.41[天文地球—矿床学]