Fluid source, element mobility and physicochemical conditions of porphyry-style hydrothermal alteration-mineralization at Mirkhani, Southern Chitral, Pakistan
Fluid source, element mobility and physicochemical conditions of porphyry-style hydrothermal alteration-mineralization at Mirkhani, Southern Chitral, Pakistan
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巴基斯坦南吉德拉尔米尔哈尼斑岩型热液蚀变成矿的流体来源、元素迁移率和物理化学条件
DOI：
10.1016/j.oregeorev.2021.104222
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发表时间：
2021-08
影响因子：
3.3
通讯作者：
Khan Asad
中科院分区：
文献类型：
--
作者：
Farhan Muhammad;Arif Mohammad;Ying Ye;Chen Xuegang;Garbe-Schonberg Dieter;Li Chun-Feng;Hussain Zahid;Ullah Zaheen;Zhang Pingping;Khan Asad
巴基斯坦开伯尔-普赫图赫瓦省米尔哈尼地区科希斯坦岛西北部的白垩纪钙碱性花岗闪长岩弧容矿斑岩型矿化。在本文中，我们提出了全岩地球化学，质量变化计算，以及类型和程度的元素活动的热液矿化蚀变过程。黄铁矿矿化有两种类型：（1）自形-半自形黄铁矿（Py 1）和碎裂黄铁矿（Py 2）。为了解热液流体的来源及其物理化学条件，测定了两类黄铁矿的微量元素和硫同位素组成。用电子探针（EPMA）分析了黄铁矿和硅酸盐矿物，平均低Ni（46）、Zn（5）、Cd（10）、Zn（10）、（低于检测水平）和Bi（1）含量（ppm），Py 1和Py 2的高Co/Ni比（>10），硫同位素Py 1（-0.84 ‰ ~ 1.49‰）和Py 2（-0.93 ‰ ~ 1.84‰）的变化表明成矿作用与长英质岩浆热液有关。硒的平均低含量和高含量（ppm）（0.7），As（2.6）、Zn（2）和Co（1089）在Py 1中比Py 2中分别（Se = 1.3，As = 4，Zn = 6和Co = 747）表明前者黄铁矿晶粒的结晶温度高于后者，这两种黄铁矿均形成于中高温条件下，其稀土元素和高场强元素的迁移性强，La/Yb比值高（平均值为0.0001 ~ 0.0001）。蚀变岩中Nb/La和Th/La比值较低（<1），反映了以富氯和富氟络合物（± SO 4和OH）为主的弱酸性溶液的活化作用。结果表明，SiO2、CaO、TiO 2被淋失，而Al 2 O3、Fe 2 O3、MgO、P2 O 5、K2 O、Cu、As、Mo、Ag、Au、Bi、REE、HFSE、和大离子亲石在热液作用过程中，亲石元素（大离子亲石元素）被富集到岩石中。成矿温度计算与脉石矿物组合类型（绿帘石+绢云母+钠长石+黄铁矿），表明成矿温度在~ 215 ℃ ~~ 322 ℃之间。热液蚀变-成矿斑岩样式、黄铁矿微量元素和硫同位素组成以及元素盈亏表明，Mirkhani成矿可能是一个主要斑岩Cu-Au系统的一部分。
The Cretaceous calc-alkaline granodioritic rocks in north-western Kohistan island arc host porphyry-type mineralization at Mirkhani in the Khyber Pakhtunkhwa province of Pakistan. In this paper, we present whole-rock geochemistry, mass-change calculations, and type and degree of element mobility regarding the hydrothermal mineralization-alteration processes. There are two distinct types of pyrite mineralization: (1) euhedral to subhedral pyrite (Py1) and cataclastic pyrite (Py2). To comprehend the source of hydrothermal fluids and their physicochemical conditions, trace element and S (sulfur) isotope compositions of the two types of pyrite were determined. Besides, the pyrite and silicate minerals were investigated through electron probe microanalysis (EPMA).The average low Ni (46), Zn (5), Cd (below detection level), and Bi (1) contents (in ppm), high Co/Ni ratio (>10) of both Py1 and Py2, and the range of sulfur isotope values for Py1 (−0.84‰ to 1.49‰) and Py2 (−0.93‰ to 1.84‰) indicate affiliation of the mineralization with felsic magma-derived hydrothermal fluids. The average low and high contents (ppm) of Se (0.7), As (2.6) and Zn (2), and Co (1089), respectively, in Py1 than Py2 (Se = 1.3, As = 4, Zn = 6 and Co = 747) indicates that former pyrite grains crystallized at a higher temperature than the latter, however, both types of pyrites were formed in medium to high-temperature conditions.The observed strong mobility of REE (rare earth elements) and HFSE (high field strength elements), high La/Yb ratios (avg. 23), and low (<1) Nb/La and Th/La ratios in the altered rocks reflect mobilization by slightly acidic solutions dominated by chloride and fluoride-rich complexes (±SO4and OH). The gain-loss calculations reveal that SiO2, CaO, and TiO2were leached out, whereas Al2O3, Fe2O3, MgO, P2O5, K2O, Cu, As, Mo, Ag, Au, Bi, and REE, HFSE, and LILE (large-ion lithophile elements) were variably added to the rocks during the hydrothermal process.Temperature calculation for chlorite formation and the type of gangue and ore mineral assemblage (epidote + sericite + albite + pyrite) implies a mineralization temperature range between ~ 215 °C and ~ 322 °C. The porphyry style of hydrothermal alteration-mineralization, trace element and S isotope composition of pyrite, and elemental gain and loss indicates that the mineralization at Mirkhani could be a part of a major porphyry Cu-Au system.
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DOI：
--
发表时间：
2009-06
期刊：
--
影响因子：
--
作者：
A. Migdisov;A. Williams-Jones
通讯作者：
A. Migdisov;A. Williams-Jones
DOI：
10.1017/s026359330001066x
发表时间：
1985
期刊：
Transactions of the Royal Society of Edinburgh: Earth Sciences
影响因子：
--
作者：
C. Pudsey;M. Coward;I. W. Luff;R. Shackleton;B. Windley;M. Q. Jan
通讯作者：
C. Pudsey;M. Coward;I. W. Luff;R. Shackleton;B. Windley;M. Q. Jan
DOI：
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发表时间：
2014
期刊：
--
影响因子：
--
作者：
A. Morikawa
通讯作者：
A. Morikawa
影响因子：
5
作者：
G. Klinkhammer;H. Elderfield;J. Edmond;A. Mitra
通讯作者：
G. Klinkhammer;H. Elderfield;J. Edmond;A. Mitra
影响因子：
--
作者：
L. Ali;B. Williamson;C. Moon;M. T. Shah;S. A. Khattak
通讯作者：
L. Ali;B. Williamson;C. Moon;M. T. Shah;S. A. Khattak