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
莫雷 1沈啟武 2陈喜连 1吴练荣 2张传昱 3董桥峰 2苏肖宇 3施宝生 2余海军 3冷成彪1
作者信息
- 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;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;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
- 折叠
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(SiO2)为 60.42%～66.44%),高Al2O3(w(Al2O3)为14.56%～16%)和高K2O(w(K2O)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.
Abstract
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 quartz-diorite porphyry exhibits medium SiO2(60.42%-66.44% ),high Al2O3(14.56%-16% ),and high K2O(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 0.705 4 to 0.706 1,and εNd(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Key words
Langdu/ore-bearing intrusion/rock geochemistry/zircon U-Pb age/Sr-Nd-Pb isotopes引用本文复制引用
基金项目
青藏高原综合科学考察研究项目(第二次)(2021QZKK0301)
国家自然科学基金(42102098)
国家自然科学基金(42173026)
云南迪庆有色金属责任公司科研项目(DQYS-SCB-08-2022031)
东华理工大学研究生创新项目(YC2023-S550)
出版年
2024
国家科技期刊平台
NSTL
万方数据