Immiscible phases derived from degassing silicate magmas are considered to be precursors of metal-bearing hydrothermal fluids in porphyry deposits. The development of melt-inclusion techniques provides a window into this critical period of porphyry formation, when the cooling, decompression, and crystallization of silicate melts result in the formation of immiscible phases. The record of magmatic to hydrothermal evolution is presented using inclusions in clinopyroxene phenocrysts from the syenitic Balut dike, one of the host-rock lithologies for mineralization at the Dinkidi Cu-Au porphyry deposit, Philippines. Primary inclusions include silicate glass, multiphase aggregates comprising salts, silicates, sulfates, carbonates, sulfides and oxides, and highly saline aqueous fluids. Various analyses, including in situ laser ablation inductively coupled plasma-mass spectrometry of the multiphase inclusions, determined elevated concentrations of Cl, S, As, Tl, K, Na, and a number of metals, including those that form ore-grade deposits (e.g., Cu) and those that do not (e.g., Mo, Pb, Zn, and W) at the Dinkidi porphyry deposit. Silicate melt and multiphase salt-rich inclusions in clinopyroxene are interpreted as having originally formed as immiscible phases at magmatic temperatures.

Item Type:	Refereed Article
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Igneous and metamorphic petrology
Objective Division:	Mineral Resources (Excl. Energy Resources)
Objective Group:	Other mineral resources (excl. energy resources)
Objective Field:	Other mineral resources (excl. energy resources) not elsewhere classified
UTAS Author:	Kamenetsky, VS (Professor Vadim Kamenetsky)
UTAS Author:	Wolfe, R (Mr Rohan Wolfe)
ID Code:	18227
Year Published:	1999
Web of Science® Times Cited:	67
Deposited By:	Centre for Ore Deposit Research - CODES CoE
Deposited On:	1999-08-01
Last Modified:	2010-08-25
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