Porphyry Cu deposits linked to episodic growth of an underlying parental magma chamber
| Autor: | Zengqian Hou, Abdul Ghaffar, Chuandong Xue, Lu Wang, Yuanchuan Zheng, William L. Griffin, Zhusen Yang, Yongjun Lu, Bo Xu, Limin Zhou |
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| Rok vydání: | 2020 |
| Předmět: |
Mineralization (geology)
010504 meteorology & atmospheric sciences Chemistry Geochemistry Magma chamber engineering.material 010502 geochemistry & geophysics 01 natural sciences Apatite Hydrothermal circulation Back-arc basin visual_art engineering visual_art.visual_art_medium General Earth and Planetary Sciences Phenocryst Plagioclase Mafic 0105 earth and related environmental sciences |
| Zdroj: | Science China Earth Sciences. 63:1807-1816 |
| ISSN: | 1869-1897 1674-7313 |
| DOI: | 10.1007/s11430-020-9634-2 |
| Popis: | Saindak is one of the typical porphyry Cu deposits (PCDs) in the Chagai magmatic arc in Pakistan. Ore-forming porphyries at Saindak PCD are mainly composed of tonalite. Here, we use geochemistry of apatite enclosed in plagioclase phenocrysts from the ore-forming tonalite to constrain the releasing and recharging processes of S and Cl in the underlying parental magma chamber during PCD mineralization. Although apatite inclusions have homogeneous intra-grain S and Cl compositions, there is significant inter-grain S and Cl variations in apatite inclusions located from core to rim in the hosting plagioclase. Such inter-grain S and Cl variation in apatites are coupled with the core-to-rim trends of An, FeO and Mg contents of the hosting plagioclase phenocryst. It indicates that the Saindak PCD likely formed by episodic injection of primitive magmas during the growth of an underlying magma chamber, rather than by one major injection or by addition of mafic melt derived from different source region. Each primitive melt injection introduced essential ore-forming materials such as S and Cl, which were rapidly and effectively released to the coexisting fluids, causing mineralization. Once primitive melt injection stops, signaling the end of growth of underlying magma chamber, mineralization will cease quickly although the hydrothermal system can still survive for a long time. However, the later released fluids are relatively depleted in ore-forming materials, and thus have lower capability to generate mineralization. Accordingly, predominant porphyry-type mineralizations occurred during the growth rather than waning stage of a magmatic system. |
| Databáze: | OpenAIRE |
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