Depositing >1.5 Mt of Tin Within <1 m.y. of Initial Granitic Intrusion in the San Rafael Tin (-Copper) Deposit, Southeastern Peru

Author:

Harlaux Matthieu12,Kontak Daniel J.3,Clark Alan H.4,Kouzmanov Kalin5,Holm-Denoma Christopher S.6,Gialli Stefano5,Laurent Oscar78,Spikings Richard5,Chauvet Alain9,Dini Andrea10,Kalinaj Miroslav11,Fontboté Lluís5

Affiliation:

1. 1 Nevada Bureau of Mines and Geology, University of Nevada, Reno, Nevada 89557-0178, USA

2. *Present address: Bureau de Recherches Géologiques et Minières (BRGMFrench Geological Survey), 45060 Orléans, France.

3. 2 Harquail School of Earth Sciences, Sudbury, Ontario P3E 2C6, Canada

4. 3 Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada

5. 4 Department of Earth Sciences, University of Geneva, 1205 Geneva, Switzerland

6. 5 U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225-0046, USA

7. 6 Institute of Geochemistry and Petrology, ETH Zürich, 8092 Zürich, Switzerland

8. **Present address: Géosciences Environnement Toulouse, CNRS-UMR 5563, Observatoire Midi-Pyrénées, Université Toulouse III Paul Sabatier, 31400 Toulouse, France.

9. 7 Géosciences Montpellier, CNRS-UMR 5243, Université de Montpellier, 34095 Montpellier, France

10. 8 Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche (CNR), 56124 Pisa, Italy

11. 9 Minsur S.A., Jr. Lorenzo Bernini 149, San Borja, Lima 27, Peru

Abstract

Abstract The San Rafael Sn (-Cu) deposit, located in the Eastern Cordillera of southeast Peru, is one of the world’s largest cassiterite-bearing vein systems (>1 Mt Sn produced since 1969). The deposit consists of a quartz-cassiterite-chlorite-sulfide lode system spatially associated with an upper Oligocene (ca. 24 Ma) S-type granitic pluton. Based on a revised paragenetic sequence for the deposit, we interpret the temporal setting of both magmatic (biotite, K-feldspar) and hydrothermal (muscovite, adularia, cassiterite) minerals analyzed by 40Ar/39Ar step-heating and U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) geochronology. The least-disturbed biotite sample from the megacrystic monzogranite yielded a 40Ar/39Ar plateau age of 24.10 ± 0.26 Ma (2σ), which constrains the time of cooling of the upper part of the pluton to below 300°C. Greisen developed on top of the granitic cupola and its immediate metamorphic aureole dated at 24.24 ± 0.24 Ma (2σ; 40Ar/39Ar muscovite average plateau age) is interpreted to be contemporaneous with the emplacement of pre-ore quartz-tourmaline veins and breccias. In situ U-Pb dating of cassiterite, including both botryoidal cassiterite (“wood tin”) and coarse-grained cassiterite in quartz-chlorite veins and breccias, constrains the timing of the main Sn ore stage to between 24.10 ± 0.37 and 23.47 ± 0.53 Ma (2σ). Botryoidal and coarse-grained cassiterite are characterized by similar trace element compositions with fluctuating metal concentrations across growth banding, suggesting significant changes of physicochemical conditions of the hydrothermal system during cassiterite precipitation, likely caused by rapid and repeated mixing between magmatic fluids and meteoric groundwaters. Polymetallic sulfide-rich veins and quartz-carbonate veins are constrained to have formed between 22.72 ± 0.11 and 22.29 ± 0.24 Ma (2σ), based on adularia 40Ar/39Ar plateau ages. The latter overlap partially reset 40Ar/39Ar age spectra for K-feldspar megacrysts in the host granite and thus reflect pervasive alteration by hydrothermal fluids. Collectively, the results show the magmatic-hydrothermal system spanned at least 2 m.y. with the main Sn ore stage representing <1 m.y. in the lifetime of the deposit. The latest polymetallic stages postdate the main Sn ore stage by ca. 1 m.y. and reflect the waning of the hydrothermal system, accompanied by additional incursion of meteoric groundwaters. This study provides further evidence that the present-day exposed level of the San Rafael granite was a passive host for the Sn mineralization and only provided the structural focusing for the mineralizing fluids derived from a deeper part of the magmatic system.

Publisher

Society of Economic Geologists, Inc.

Subject

Economic Geology,Geochemistry and Petrology,Geology,Geophysics

Reference124 articles.

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3