The Altar porphyry Cu-(Au-Mo) deposit (Argentina): a complex magmatic-hydrothermal system with evidence of recharge processes Public Deposited

http://ir.library.oregonstate.edu/concern/articles/s7526f07q

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  • Altar (31º 29’ S, 70º 28’ W) is a large porphyry Cu-(Au-Mo) deposit with associated epithermal Au-(Ag-Cu) veins located in the Cordillera Principal of SW San Juan Province (Argentina). Altar is a complex magmatic-hydrothermal system formed from several magmatic and hydrothermal pulses during the middle-late Miocene. New LA-ICPMS U-Pb ages in zircons from the Altar porphyries indicate four discrete events of intrusions over an extended magmatic life time of ca. 3 m.y. It comprises a pre-mineralization porphyry (11.75 ± 0.24 Ma), three mineralized porphyries (11.62 ± 0.21 Ma and 11.68 ± 0.27 Ma, 11.13 ± 0.26 Ma, 10.35 ± 0.32 Ma) related to hydrothermal breccias, two post-mineralization intrusions, and a post-mineralization breccia (8.9 ± 0.4 Ma). The three mineralized porphyries (porphyries 2, 3 and 4) were emplaced within ~0.7-1.3 m.y. Amphibole phenocrysts from the porphyries crystallized from oxidized magmas (fO₂=NNO +1 to +2) at temperatures of 780 to 850°C and pressures between 0.9 and 1.8 kbar corresponding to depths of ~4-7 km. Anorthite and Fe- rich rims in the plagioclase phenocrysts suggest that the magmatic chambers were episodically recharged by a less evolved magma. The middle-late Miocene intrusions are interpreted to have been derived from a deeper and relatively large magmatic reservoir that supplied magmas to smaller chambers located in the upper crust. The focused magmatic output to shallow levels during a period of a few million years in the Altar area has been a main requirement in the formation of this large porphyry copper deposit.
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  • Maydagan, L., Franchini, M., Chiaradia, M., Dilles, J., & Rey, R. (2014). The Altar porphyry Cu-(Au-Mo) deposit (Argentina): A complex magmatic-hydrothermal system with evidence of recharge processes. Economic Geology, 109(3), 621-641. doi:10.2113/econgeo.109.3.621
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  • description.provenance : Submitted by Erin Clark (erin.clark@oregonstate.edu) on 2014-07-10T20:33:47Z No. of bitstreams: 1 DillesJohnCEOASAltarPorphyryDeposit.pdf: 3288596 bytes, checksum: 9ae6e3264767f76edd35fc684a9f6273 (MD5)
  • description.provenance : Made available in DSpace on 2014-07-10T20:33:59Z (GMT). No. of bitstreams: 1 DillesJohnCEOASAltarPorphyryDeposit.pdf: 3288596 bytes, checksum: 9ae6e3264767f76edd35fc684a9f6273 (MD5) Previous issue date: 2014-05
  • description.provenance : Approved for entry into archive by Erin Clark(erin.clark@oregonstate.edu) on 2014-07-10T20:33:59Z (GMT) No. of bitstreams: 1 DillesJohnCEOASAltarPorphyryDeposit.pdf: 3288596 bytes, checksum: 9ae6e3264767f76edd35fc684a9f6273 (MD5)

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