Equilibrium partitioning and subsequent re-distribution of halogens among apatite–biotite–amphibole assemblages from mantle-derived plutonic rocks: Complexities revealed

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

“…In addition, melt inclusions that might have preserved the volatile content at magmatic conditions are not always available (or large enough) within the crystal cargo of magmatic rocks. Nevertheless, common hydrous minerals such as biotite, amphibole and apatite may keep record of the evolution of various volatiles in the magma from which they crystallized (e.g., Coulson et al 2001;Parat et al 2011a;Zhang et al 2012Zhang et al , 2017Rasmussen and Mortensen 2013;Chambefort et al 2013;Van Hoose et al 2013;Teiber et al 2015;Scott et al 2015;Bao et al 2016).…”

Tectonic Settings of Potassic Igneous Rocks

“…Therefore, significant exogenous water (>3 wt%) must be added to the mantle source in order to produce the hydrous melts required . The exogenous water, as well as the LILE, LREE and halogens, are mainly incorporated in hydrous phenocrysts such as phlogopite and/or amphibole (Aoki et al 1981;Fuge et al 1986;Righter et al 2002;Yang and Lentz 2005;Sarjoughian et al 2014;Teiber et al 2015). As a result, portions of the Earth's upper mantle rich in phlogopite ± clinopyroxene are considered to be important in the genesis of potassic melts (Edgar and Arima 1985;Foley 1992;Till et al 2012;Guo et al 2013;Lu et al 2013a).…”

Halogen Contents of Mineralized Versus Unmineralized Potassic Igneous Rocks

“…Experimental studies by Vukadinovic and Edgar (1993) suggest that F, in contrast to Cl (see Magenheim et al 1995), behaves as a mantle-compatible element. This can be explained by the relatively small ionic radius of the F cation when compared to the larger and probably more incompatible Cl anion (Teiber et al 2015). Although, under mantle conditions, F tends to remain in the solid phases rather than partitioning into the first melt increments during partial melting (Vukadinovic and Edgar 1993), alkaline rocks derived in within-plate settings such as OIB are defined by relatively high F concentrations of 900-1100 ppm (cf.…”

“…The strong affinity of the halogens for potassium, particularly in micas, can be explained in terms of their electronic configurations (Cocco et al 1972). The Cl-OH and F-OH exchange in the hydroxyl site of micas is susceptible to interaction with hydrothermal fluids, which may impact cations in the octahedral sites given the presence of correlation between (F-Cl-OH) and (Al + Ti + Fe 3 + Cr) (see Righter et al 2002;Yang and Lentz 2005;Teiber et al 2015). Due to the similar ionic radii of F − (1.33 Å; Shannon 1976) and OH − (1.32-1.37 Å), F − is much easily incorporated into OH-bearing minerals than the larger Cl − (1.81 Å).…”

“…Due to the similar ionic radii of F − (1.33 Å; Shannon 1976) and OH − (1.32-1.37 Å), F − is much easily incorporated into OH-bearing minerals than the larger Cl − (1.81 Å). Hence, at the magmatic-hydrothermal transition, F is largely retained in the melt whereas Cl preferentially partitions into the fluid phase (Webster et al 2009;Wang et al 2014;Teiber et al 2015). The potential use of high Cl concentrations in mica phenocrysts as a prospecting tool to define mineralized volcanic and subvolcanic rocks was first suggested by Stollery et al (1971).…”