投稿时间：2024-03-22
修订日期：2024-06-08
网络发布日期：2024-11-05
中文摘要:玻利维亚锡矿带是全球最重要的锡多金属成矿带之一，与其他地区锡矿普遍与花岗岩密切相关不同，该带锡矿区内并无花岗岩出露，锡矿体主要赋存于次火山岩中，因此锡矿与次火山岩的成因关系是长期备受关注的重要科学问题。Llallagua斑岩型锡矿位于玻利维亚锡多金属成矿带中部地区，是全球最大的锡矿之一。已有研究根据区内流纹质斑岩形成时代明显早于锡成矿时代，认为锡矿与区内赋矿次火山岩无关。然而，Llallagua锡矿体主要呈脉状产于英安斑岩中，而目前英安斑岩与锡矿的时间关系尚不清楚。文章在详细野外地质观察的基础上，选取与锡矿空间关系密切的英安斑岩开展系统的年代学研究，并系统梳理了整个玻利维亚锡矿带内岩浆活动和锡成矿时空格架及二者的关系。结果表明，2件英安斑岩样品锆石LA-ICP-MS U-Pb年龄为（21.8±0.1）Ma和（21.3±0.3）Ma，与前人获得锡矿脉中独居石U-Pb年龄（23.4±2.2）Ma以及锡石U-Pb年龄（24.0±5.1）Ma在误差范围内基本一致，表明锡矿与赋矿次火山岩具有密切的时间关系。考虑到锡矿体呈脉状产出于英安斑岩内以及英安斑岩本身分异程度较弱，文章认为英安斑岩并非锡矿的成矿岩体，推测深部存在与英安斑岩同期隐伏的锡矿成矿岩体。此外，整个成矿带成岩内成矿年龄系统梳理显示，区域上斑岩型锡矿和赋矿次火山岩亦基本同时形成，整个玻利维亚锡矿带的岩浆作用和锡成矿时代可以分成2个阶段：三叠纪至侏罗纪和晚渐新世至中新世。其中，三叠纪至侏罗纪锡矿主要分布在玻利维亚锡多金属成矿带的北部地区，而晚渐新世至中新世锡矿在整个带内均有分布并且具有从北向南逐渐变年轻的趋势。
中文关键词:次火山岩 成矿年龄 Llallagua锡矿 玻利维亚锡矿带
Abstract:The Bolivian tin belt is one of the most important tin polymetallic metallogenic belts in the world. In this belt, tin ore bodies are mainly hosted in subvolcanic rocks and there is no granite in the tin mining area, which is obviously different from close relationship between tin deposit and granite in other tin deposit globally. The temporal relationship between the sub-volcanic rocks and tin deposit still remains unclear. The Llallagua tin deposit, located in middle part of the Bolivian tin belt, is one of the largest tin deposits in the world. Previous studies found that the rhyolite porphyry is much older than tin mineralization, suggesting that tin ore has no temporal and genetic relationship with the ore-hosted subvolcanic rocks. However, the tin ore bodies is mainly hosted in dacite porphyry as veins and the temporal and genetic relationships between the dacite porphyry and tin deposit remain unclear. Base on detailed field geological observation, this study reports the geochronological data of the ore-hosted dacite porphyry. The LA-ICP-MS U-Pb ages of zircons from two samples of dacite porphyry are (21.8±0.1) Ma and (21.3±0.3) Ma, which is well consistent with the previous reported U-Pb age of monazite (23.4±2.2) Ma and the U-Pb age of cassiterite (24.0±5.1) Ma from the tin veins. It indicates that the tin ore and the ore-bearing subvolcanic rocks have a close temporal relationship. Considering that the tin ore bodies are vein-like within the dacite porphyry and the dacite porphyry itself has limited mineralization potential, we think that the dacite porphyry is not the ore-forming rock for tin ore, and we speculate that there are contemporaneous concealed ore-forming rocks for tin ore deep underground associated with the monzogranite. Furthermore, the results of the petrological and metallogenic chronological framework show that the regional porphyry tin deposits and the ore-bearing subvolcanic rocks were also formed at the same time. Finally the timing of magmatic rocks and tin deposits of the Bolivian tin belt can be divided into two stages: Triassic to Jurassic and Late Oligocene to Miocene. The Triassic to Jurassic tin deposits are mainly distributed in North area of the belt. The Oligocene and Miocene tin deposits are distributed in all belt and became younger from the North to the South.
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基金项目:本文得到国家自然科学基金项目（编号:42330814、42472143）资助
引用文本：
王嘉旭,宋以龙,赵盼捞,张璐,袁顺达.2024.斑岩型锡矿与赋矿次火山岩的关系：来自玻利维亚锡矿带Llallagua锡矿床年代学证据[J].矿床地质,43(5):1164~1174WANG JiaXu,SONG YiLong,ZHAO PanLao,ZHANG Lu,YUAN ShunDa.2024.Relationship between porphyry tin deposit and ore-bearing subvolcanic rocks: Geochronological evidence from Llallagua tin deposit in Bolivian tin belt[J].Mineral Deposits43(5):1164~1174
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