A Reevaluation of the Timing and Temperature of Copper and Molybdenum Precipitation in Porphyry Deposits

石英 地质学 斑岩铜矿 地球化学 流体包裹体 岩相学 围岩 辉钼矿 静脉 硅酸盐 矿物学 冶金 化学 材料科学 古生物学 有机化学 精神科 心理学
作者
F. Cernuschi,John H. Dilles,Jaime Osório,John M. Proffett,Kalin Kouzmanov
出处
期刊:Economic geology and the bulletin of the Society of Economic Geologists [Society of Economic Geologists]
卷期号:118 (5): 931-902 被引量:11
标识
DOI:10.5382/econgeo.5032
摘要

Abstract The timing and temperature at which copper-iron and molybdenum sulfide deposition occurs in porphyry deposits remain controversial. Petrologic estimates indicate that veins and wall-rock alteration zones containing copper-iron sulfides form in a wide temperature range from ~350° to 650°C. Most sulfides are hosted in potassium(K)-silicate–altered rock and quartz A veins or in early-halo alteration selvages formed above ~450°C. In contrast, cathodoluminescence (CL) imaging of A veins indicates that copper-iron sulfides are contained within a primary lucent (bright and gray)-CL quartz and are crosscut by microfractures filled with younger dull (dark and medium-gray)-CL quartz in direct contact with copper-iron sulfides. These observations have been interpreted as supporting late copper-iron sulfide introduction together with dull-CL quartz at moderate temperatures of ~300° to 450°C, based on fluid inclusion estimates. We provide new CL, QEMSCAN, and petrographic data and images of vein quartz as well as petrologic data of altered wall rock from Haquira East (Peru), Encuentro (Chile), and Batu Hijau (Indonesia) porphyry deposits, which were formed at conditions ranging from deep to shallow (~2–10 km). At all three deposits, dull-CL quartz in microfractures is ubiquitously observed crosscutting all generations of high-temperature lucent-CL quartz veins. Each lucent-CL vein type hosts distinct sulfide populations, crosscuts the others, and coexists in space within the copper and molybdenum ore zones. Within this ore zone, the dull-CL quartz only contains copper-iron sulfides where it transects old A veins and early halos, molybdenite where it transects young molybdenite-bearing quartz veins, and both copper-iron sulfides and molybdenite in younger B veins. Furthermore, where the dull-CL quartz crosscuts igneous or barren (deep) quartz veins, it typically lacks copper and molybdenum. Therefore, dull-CL quartz has no particular spatial or genetic affinity with copper-iron sulfides or molybdenite. We propose that copper was introduced and precipitated at high temperatures in stability with K-silicate alteration. In shallow porphyry deposits, most copper was introduced with lucent-CL quartz in A veins, likely formed via adiabatic decompression from magmatic lithostatic to hydrostatic conditions at ~450° to 600°C. In deep deposits, most copper is introduced with quartz-poor early halos, likely formed at a temperature range similar to that of A veins but during an early stage of retrograde silica solubility. The inferred timing and temperature of copper precipitation are consistent with available solubility experiments for copper-bearing solutions that suggest copper precipitation may start at a high temperature of ~600°C, and ~90% precipitates before it cools down to ~400°C. Much of the molybdenum is introduced and precipitated with discrete pulses of molybdenite-bearing quartz veins that crosscut and postdate copper-bearing A veins and early halos and, to a lesser degree, with B veins that may carry both copper and molybdenum. Whereas molybdenite-bearing and barren (deep) quartz veins form at relatively high temperatures of ~550° to 650°C, copper-molybdenum–bearing B veins likely form at lower temperatures near ~500°C. Copper precipitation and local copper remobilization from older veins and halos continued during the formation of copper-iron sulfide veinlets, named C veins, and during the precipitation of dull-CL quartz following K-silicate alteration. C veins and even younger pyrite-rich D veins may have chlorite or sericite selvages and are composed of dull-CL quartz that formed at ~450° and 300° to 450°C, respectively. Microfractures form through all lucent-CL quartz veins because of the thermal contraction of high-temperature quartz at the onset of sustained cooling after K-silicate alteration has ceased. The fluid that migrated through these microfractures was initially in retrograde silica solubility, which causes dissolution and corrosion of the older lucent-CL quartz. The formation of C veins may overlap in time with the initial stage. At a later stage and temperatures below <450°C, the fluid precipitates dull-CL quartz in microfractures and dissolution zones within older lucent-CL quartz. In copper-iron sulfide-bearing A and B veins and molybdenite-bearing quartz veins, corroded lucent-CL quartz and the younger dull-CL quartz infill can often be observed in contact with older sulfides because quartz sulfide grain boundaries are preexisting discontinuities, and they are preferentially opened during volume contraction. Collectively, these observations and estimates are consistent with silicate phase petrology and numerous observations that most copper-iron sulfides precipitate in K-silicate alteration zones or in early halos with K-feldspar-muscovite-biotite assemblages.

科研通智能强力驱动
Strongly Powered by AbleSci AI
科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
1秒前
萤火虫发布了新的文献求助10
1秒前
赘婿应助洁净的夜云采纳,获得10
1秒前
张欢馨应助GXP采纳,获得10
2秒前
iceice发布了新的文献求助10
2秒前
3秒前
4秒前
斯信荣发布了新的文献求助10
5秒前
Owen应助xh采纳,获得10
5秒前
5秒前
略略略发布了新的文献求助10
5秒前
zhezhe煲完成签到,获得积分10
5秒前
Akim应助Rrr采纳,获得10
5秒前
6秒前
洋芋完成签到,获得积分10
7秒前
啦啦啦发布了新的文献求助10
7秒前
斯文败类应助简单学姐采纳,获得10
7秒前
Akim应助任性jyjh采纳,获得10
8秒前
皮蛋solo粥发布了新的文献求助10
8秒前
8秒前
jie发布了新的文献求助10
9秒前
Menglong发布了新的文献求助10
9秒前
科研通AI6.4应助宋娜采纳,获得10
9秒前
归尘发布了新的文献求助30
10秒前
10秒前
SerCheung完成签到,获得积分10
10秒前
11秒前
11秒前
11秒前
易玟完成签到,获得积分10
11秒前
12秒前
王坤完成签到,获得积分10
12秒前
12秒前
寒冷的雅寒完成签到,获得积分10
12秒前
吴竟钊发布了新的文献求助10
12秒前
完美世界应助xiaoxuey采纳,获得10
13秒前
跳跃的太阳完成签到,获得积分10
13秒前
科研通AI6.4应助ll200207采纳,获得10
14秒前
bluebear完成签到,获得积分10
14秒前
混日子呢完成签到,获得积分10
15秒前
高分求助中
(应助此贴封号)【重要!!请各用户(尤其是新用户)详细阅读】【科研通的精品贴汇总】 10000
Römisch-Germanische Forschungen 1000
APA handbook of comparative psychology: Basic concepts, methods, neural substrate, and behavior 1000
Matrix Methods in Data Mining and Pattern Recognition Second Edition 510
The fast track to determining transfer functions of linear circuits: The student guide 500
Electric machines: theory, operating applications, and controls 500
The Analytical and Numerical Solution of Electric and Magnetic Fields 500
热门求助领域 (近24小时)
化学 材料科学 医学 生物 纳米技术 工程类 有机化学 化学工程 生物化学 计算机科学 内科学 物理 复合材料 催化作用 细胞生物学 无机化学 光电子学 物理化学 电极 基因
热门帖子
关注 科研通微信公众号,转发送积分 7603819
求助须知:如何正确求助?哪些是违规求助? 9179638
关于积分的说明 19659443
捐赠科研通 7178880
什么是DOI,文献DOI怎么找? 3269212
关于科研通互助平台的介绍 2433325
邀请新用户注册赠送积分活动 2263229