Fluid-assisted interaction of peraluminous metapelites with trondhjemitic magma within the Petronella shear-zone, Limpopo Complex, South Africa

Involvement of fluids in the metamorphic processes within different zones of the Southern Marginal Zone of the Limpopo complex, South Africa: An oxygen isotope perspective

“…Whole rock chemical composition of the metapelite samples (Table 2) falls within the range characteristic of the Bandelierkop formation (Kreissig et al, 2000). The leucogranite is similar in composition to that at Bandelierkop (see below) and Petronella (Safonov et al, 2014) localities. The metapelites are composed of variable proportions of Grt, Opx, Bt, Pl, and Qtz (Table 1).…”

Fluid-rock interaction during high-grade metamorphism: Instructive examples from the Southern Marginal Zone of the Limpopo Complex, South Africa

“…The fluid-assisted model is also supported by the common occurrence of CO2, brine and mixed CO2-brine fluid inclusions (e.g., Touret, 2012;Touret and Huizenga, 2011;Aranovich et al, 2013;Newton et al, under review;Safonov et al, under review). Finally, the presences of large volumes of anatectic granitic melt in high-grade metamorphic terrains argue in favour of a mechanism of "water-fluxed melting" (e.g., Sawyer et al, 2011).…”

“…The reasons why researchers often doubt whether infiltration metasomatism is widespread during regional metamorphism appears to arise from concerns about the availability and source of fluids (e.g., Yardley, 2013). However, recent experimental data (e.g., Newton and Manning, 2010;Aranovich et al, 2013, under review;Safonov et al, under review) clearly show that, regardless of their origin, deep crustal fluids and specifically brines, must be important agents of metasomatism and mass transfer wherever such processes are recognized in the field or hand specimen (e.g., Harlov, 2012).…”

“…On the other hand, proponents of the fluid-assisted model for granulite formation and for associated anatexis have shown that temperature estimates (T < 850°C) obtained by geothermobarometry from numerous "normal" granulite facies rocks are in fact lower than the values required for the onset of fluid-absent dehydration melting (Aranovich et al, 1987, under review;Newton, 1989;Johannes and Holtz, 1991;Newton et al, 1998, under review;Nair and Chacko, 2002;Safonov et al, under review). They ascribe the apparent undisturbed protolith O-isotope signatures of granulite to low fluid/rock ratios (e.g., Hoernes et al, 1995).…”

High- to ultrahigh-temperature metasomatism related to brine infiltration in the Neoarchean Limpopo Complex: Petrology and phase equilibrium modeling

“…Although fluids released by crystallizing anatectic melts and fluids derived from the upper mantle might have been involved, all available evidences point to devolatilization of greenstone materials (metasediments and metavolcanics) as the result of thrusting hot granulite of the SMZ onto cool granite-greenstone belts of the Kaapvaal Craton as the most likely source for infiltrating immiscible H 2 O-CO 2 and brine fluids. Fluids thus released interacted with the granulites to trigger the major pulse of anatexis (Safonov et al, 2014) and metasomatism at high T (∼850 • C) (e.g., Van Reenen et al, 2014), and regional rehydration of granulites at lower temperatures (<700 • C) (e.g., Van Reenen, 1986;Koizumi et al, 2014).…”