Magmatic Fluid Inclusions from the Zaldivar Deposit, Northern Chile: The Role of Early Metal‐bearing Fluids in a Porphyry Copper System

Abstract

Abstract:The occurrence of a distinct type of multi-solid, highly-saline fluid inclusions, hosted in igneous quartz phenocrysts from the Llamo porphyry, in the Zaldívar porphyry copper deposit of northern Chile is documented. Total homogenization of the multi-solid type inclusions occurs at magmatic temperatures (over 750°C), well above the typical temperatures of hydrothermal fluids (less than 600°C) usually recorded in porphyry copper systems. The analysis of this type of fluid inclusions, using a combination of non-destructive microthermometry, Raman and PIXE techniques and the identification of daughter minerals by SEM method, indicates that the trapped fluid was a dense, complex chloride brine in which Cl, Na, K, Fe, Cu, and Mn are dominant. The high chlorine and metal contents indicate that the metals were separated from the crystallizing magma as homogeneous aqueous chloride-rich solutions that represent the primary magmatic fluids exsolved at high temperatures and depth during the crystallization of the parental intrusive.The multi-solid type inclusion illustrates the mechanism by which ore components are sequestered from the crystallizing parental magma and concentrated in the exsolved magmatic aqueous fluids. These fluids are significant with respect to the origin of porphyry copper deposits, as they are responsible for the first enrichment of metals and represent the precursors of metal-bearing hydrothermal fluids in a porphyry copper system.

Heterogeneous melt and hypersaline liquid inclusions in shallow porphyry type mineralization as markers of the magmatic-hydrothermal transition (Cerro de Pasco district, Peru)

“…These results discard the hypothesis that the studied HSMIs are the entrapment product of a single "supercritical melt" and favor the heterogeneous entrapment of two fluids including a silicate melt and a chlorine-rich fluid. Heterogeneous entrapment has already been proposed by several authors to explain presence of HSMIs in magmatic quartz phenocrysts and miarolitic cavities (Campos et al, 2002(Campos et al, , 2006Davidson et al, 2005;Davidson and Kamenetsky, 2007;Frezzotti, 1992;Fulignati et al, 2005;Harris et al, 2004;Kamenetsky et al, 2004;Kamenetsky and Kamenetsky, 2010;Lowenstern, 1994;Zajacz et al, 2008) and in quartz from porphyry quartz veins (Harris et al, 2003;Pintea, 1995 and2012). At Cerro de Pasco, a heterogeneous entrapment scenario is supported by (1) an extremely variable melt/globule ratio in the HSMIs (Figs.…”

“…A striking characteristic of this porphyry-style mineralization is the occurrence of inclusions in the hydrothermal quartz consisting of variable proportions of silicate melt and non-silicate chlorinerich fluid, hereafter referred to as heterogeneous silicate melt inclusions (HSMIs). HSMIs have been observed occasionally in various occurrences in quartz phenocrysts from intrusive rocks, miarolitic cavities and pegmatites (Campos et al, 2002(Campos et al, , 2006Davidson et al, 2005;Davidson and Kamenetsky, 2007;Frezzotti, 1992;Fulignati et al, 2005;Harris et al, 2004;Kamenetsky et al, 2004;Kamenetsky and Kamenetsky, 2010;Lowenstern, 1994;Davidson, 2013, 2016;Zajacz et al, 2008).…”

Immiscibility of magmatic fluids and their relation to Mo and Cu mineralization at the Bangpu porphyry deposit, Tibet, China

“…SEM-EDS also revealed elevated contents of Mn, Cu and Pb. This is to be expected because the inner walls of the open cavity are usually encrusted with material that contains traces of Mn, Cu and Pb (Campos et al, 2006). All above observations indicate that the fluid trapped in the polyphase fluid inclusions corresponds to a dense, chlorine-rich, Fe-, Mn-, Cu-and Pb-bearing fluid.…”

High-temperature magmatic fluid exsolved from magma at the Duobuza porphyry copper-gold deposit, Northern Tibet

“…2010); (ii) direct exsolution from the magma (Roedder & Coombs 1967; Cline & Bodnar 1991; Lowenstern 1994; Shinohara 1994; Bodnar 1995; Kamenetsky et al. 1999; Campos et al. 2002, 2006; Veklser 2004; Webster & Mandeville 2007).…”

“…Cline & Bodnar 1991; Shinohara 1994; Bodnar 1995; Kamenetsky et al. 1999; Campos et al. 2006; Webster & Mandeville 2007).…”