Curtin University Homepage
  • Library
  • Help
    • Admin

    espace - Curtin’s institutional repository

    JavaScript is disabled for your browser. Some features of this site may not work without it.
    View Item 
    • espace Home
    • espace
    • Curtin Research Publications
    • View Item
    • espace Home
    • espace
    • Curtin Research Publications
    • View Item

    Phenocryst zonation in porphyry-related rocks of the Baguio District, Philippines: Evidence for magmatic and metallogenic processes

    Access Status
    Fulltext not available
    Authors
    Cao, Mingjian
    Evans, Noreen
    Hollings, P.
    Cooke, D.
    McInnes, Brent
    Qin, K.
    Li, G.
    Date
    2018
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Cao, M. and Evans, N. and Hollings, P. and Cooke, D. and McInnes, B. and Qin, K. and Li, G. 2018. Phenocryst zonation in porphyry-related rocks of the Baguio District, Philippines: Evidence for magmatic and metallogenic processes. Journal of Petrology. 59 (5): pp. 825-848.
    Source Title
    Journal of Petrology
    DOI
    10.1093/PETROLOGY/EGY046
    ISSN
    0022-3530
    School
    John de Laeter Centre
    URI
    http://hdl.handle.net/20.500.11937/71163
    Collection
    • Curtin Research Publications
    Abstract

    © The Author(s) 2018. Published by Oxford University Press. All rights reserved. Mantle-derived mafic magmas may be the source of ore-forming metals in large Cu porphyry systems, but evidence of primary petrogenetic and metallogenetic processes can be masked by hydrothermal alteration. The Baguio district of Northern Luzon, Philippines is a world-class mineral province containing approximately 40 Moz of gold and 5 Mt of copper, distributed across many porphyry Cu and epithermal Au deposit systems which are spatially related to Pliocene pre-ore Liw-Liw Creek (LCC) basaltic dikes (3.59-4.73 Ma) and a syn-ore plagioclase-hornblende diorite porphyry (2.81-2.98 Ma). A range of phenocryst phases (plagioclase, amphibole and clinopyroxene) are well preserved in both the basaltic dike suite and diorite porphyry suite, and provide an excellent natural laboratory to investigate magmatic processes and the relationship between metallogenesis and mafic magma. Widespread normally zoned clinopyroxene and amphibole grains in the basaltic dike suite show sharp decreases in Mg#, but increasing Mn, Sr, Cu, Y, Zr and REE from core to rim. Mixing of evolved felsic magma into the mafic magma is the most likely cause of these trends as fractional crystallization would typically result in gradual variations. In the diorite porphyry suite, reversely zoned amphibole is characterised by sharp increases in Mg#, Cu and Ni, but decreasing Mn, while oscillatory zoned plagioclase with distinct regions of patchy zonation shows repeated variations of An, Mg, Fe and Sr from core to rim. These signatures indicate the addition of basaltic magma to the diorite porphyry magma. The modeled Mg# of the melts (estimated assuming mineral-melt equilibrium) is also consistent with magma mixing. For example, the high Mg# of 66-72 and low Mg# of 38-44 estimated from the LLC clinopyroxene cores and rims, respectively, support the presence of basaltic magma, mixed with evolved felsic magma. All normally zoned clinopyroxene and amphibole in the basaltic dike suite and reversely zoned amphibole in the diorite porphyry suite show consistent increases in Cu from core to rim, suggesting relative enrichment of Cu in both types of injected magma. The pre-ore basaltic and ore-forming dioritic hybrid melts are estimated to have contained 45-96ppm and 319-351ppm Cu, respectively, based on Cu partition coefficients and zone area percentage. The Cu content of the basaltic hybrid melt is typical of arc magmas (Cu 50-100 ppm), whereas the Cu in the dioritic melt was 3-6 times higher than typical arcs magma. Both the clinopyroxene-melt thermobarometer and Al-in-hornblende geobarometer indicate similar crystallization pressures for both suites (8.6~8.8, 4.4~4.7, 2.1~2.8 kbar), suggesting that both pre-ore basaltic and syn-ore dioritic suites formed in different magma chambers at similar depths. The addition of Cu enriched mafic magma may contribute ore-forming elements to the mineralising magmas and significantly increase the mineralization potential of coeval felsic rocks. Studies of phenocrysts have the potential to elucidate the role of magmatic process in the formation of porphyry systems and allow for the recognization of the key characteristics of fertile magmatic systems.

    Related items

    Showing items related by title, author, creator and subject.

    • Volatile variations in magmas related to porphyry Cu-Au deposits: Insights from amphibole geochemistry, Duolong district, central Tibet
      Li, J.; Qin, K.; Li, G.; Evans, Noreen; Zhao, J.; Yue, Y.; Xie, J. (2018)
      Ore-forming fluid exsolution in a shallow magma chamber is a critical step in the formation of porphyry Cu ± Mo ± Au deposits but one for which direct evidence is rarely found. Here, Cl abundance, major-trace element ...
    • Late Carboniferous high εNd(t)– εHf(t) granitoids, enclaves and dikes in western Junggar, NW China: Ridge-subduction-related magmatism and crustal growth
      Tang, G.; Wang, Q.; Wyman, D.; Li, Zheng-Xiang; Zhao, Z.; Yang, Y. (2012)
      We report results of petrologic, geochronological and geochemical investigation of the Late Carboniferous diorites, granodiorites, amphibole (Am)-bearing granites, and associated dioritic and monzonitic enclaves and mafic ...
    • Physicochemical processes in the magma chamber under the Black Mountain porphyry Cu-Au deposit, Philippines: Insights from mineral chemistry and implications for mineralization
      Cao, Mingjian; Hollings, P.; Cooke, D.; Evans, Noreen; McInnes, Brent; Qin, K.; Li, G.; Sweet, G.; Baker, M. (2018)
      The Black Mountain porphyry Cu-Au deposit in the Baguio district, Northern Luzon (Philippines) is associated with late Miocene to Pliocene intrusive rocks that retain primary crystallization signatures, providing an ...
    Advanced search

    Browse

    Communities & CollectionsIssue DateAuthorTitleSubjectDocument TypeThis CollectionIssue DateAuthorTitleSubjectDocument Type

    My Account

    Admin

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Follow Curtin

    • 
    • 
    • 
    • 
    • 

    CRICOS Provider Code: 00301JABN: 99 143 842 569TEQSA: PRV12158

    Copyright | Disclaimer | Privacy statement | Accessibility

    Curtin would like to pay respect to the Aboriginal and Torres Strait Islander members of our community by acknowledging the traditional owners of the land on which the Perth campus is located, the Whadjuk people of the Nyungar Nation; and on our Kalgoorlie campus, the Wongutha people of the North-Eastern Goldfields.