Collision‐related porphyry Cu deposits formed by input of ultrapotassic melts into the sulfide‐rich lower crust

Collision‐related porphyry Cu deposits (PCDs) are restricted to previous magmatic arcs, in which sulfide‐rich lower crust occurred. Fertile adakite‐like porphyries associated with PCDs have higher K2O contents and K2O/Na2O ratios than barren porphyries emplaced in the same arc. The elevated K2O/Na2O...

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Bibliographic Details
Published in:Terra nova (Oxford, England) England), 2021-12, Vol.33 (6), p.582-589
Main Authors: Zheng, Yuan‐Chuan, Shen, Yang, Wang, Lu, Griffin, William L., Hou, Zeng‐Qian
Format: Article
Language:English
Subjects:
Fertility
Isotopes
Juveniles
Moisture content
Ratios
Sulfides
Sulphides
Water content
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Summary:Collision‐related porphyry Cu deposits (PCDs) are restricted to previous magmatic arcs, in which sulfide‐rich lower crust occurred. Fertile adakite‐like porphyries associated with PCDs have higher K2O contents and K2O/Na2O ratios than barren porphyries emplaced in the same arc. The elevated K2O/Na2O ratios of fertile porphyries reflect substantial inputs of coeval hydrous, oxidized ultrapotassic melts. Input of such melts could increase the water content and oxygen fugacity of the lower‐crust‐derived melts, which in turn would promote the breakdown of sulphides in the lower crust and increase the contents of Cu and S in the melts, making them favourable for the formation of large PCDs. The relatively low K2O contents and K2O/Na2O ratios of barren porphyries indicate limited input of ultrapotassic melts; these magmas have low potential to form PCDs. Thus, the input of ultrapotassic melts into the sulfide‐rich juvenile lower crust drives the formation of collision‐related PCDs.
ISSN:0954-4879
1365-3121
DOI:10.1111/ter.12550