Fluid migration along deep‐crustal shear zone: A case study of the Rhenosterkoppies Greenstone Belt in the northern Kaapvaal Craton, South Africa

The north-dipping Hout River Shear Zone (HRSZ), which marks the boundary between high-grade Limpopo Complex in its hanging wall and low-grade granite-greenstone terrane of Kaapvaal Craton South Africa footwall, is a deep-crustal shear zone that controlled emplacement hot granulites over against granite-greenstones during exhumation at ~2.72–2.62 Ga. This major migration large volumes hydrous fluids released devolatilization underthrusted greenstones infiltrated into overlying granulites, establishing retrograde anthophyllite-in isograd associated rehydrated granulite bounds south. Here, we report new petrological data based on mineral equilibrium modelling amphibolites from Rhenosterkoppies Greenstone Belt (RGB) located immediate footwall HRSZ discuss evidence these rocks also interacted with high-temperature along HRSZ. study provides an important perspective interaction relatively cold greenschist-facies steeply section HRSZ, shows for such restricted to narrow termed hot-iron-zone. peak assemblage garnet-free amphibolite RGB (magnesio-hornblende + plagioclase quartz clinopyroxene titanite ilmenite) yielded P–T condition 7–8 kbar 640–680°C H2O content 3.5–3.8 mol%. Clinopyroxene replaced by actinolite epidote symplectites post-peak hydration event <5 <590°C caused elevated rock (>4.0 mol%), possibly related fluid infiltration Mineral equilibria garnet-bearing records prograde path 5 7 540–630°C conditions 7.6–8.7 620–650°C. A clockwise suggesting rapid compression decompression has been inferred RGB, because pressure increase overthrusting (Southern Marginal Complex) onto terrane, followed exhumation. quantity amphibolite-facies metamorphism was stage (M(H2O) = mol%) 4.0–4.5 not only internal sources but external sources. results this indicate H2O-bearing fluid, affected both sections zone, although effect limited.