Petrology and Mineral Chemistry of Lower Crustal Intrusions: the Chilas Complex, Kohistan (NW Pakistan)

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

“…Instead the oceanic arc is plastered to the edge of the continental mass, effectively as a coherent block with no opportunity for major crustal loss by subduction. A number of the better known examples of oceanic arcs in mountain belts appears to have been accreted in this fashion, most notably the Jurassic Talkeetna Arc in SE Alaska (DeBari and Coleman, 1989;Greene et al, 2006) and the Cretaceous Kohistan Arc (Treloar et al, 1996;Khan et al, 1997;Jagoutz et al, 2007) of the western Himalayas. In both these examples the full crustal section is preserved, suggesting a very efficient accretionary process.…”

High-K ankaramitic melt inclusions and lavas in the Upper Cretaceous Eastern Srednogorie continental arc, Bulgaria: Implications for the genesis of arc shoshonites

“…Recently, such melts have been successfully obtained in melting experiments with variable Ca-rich pyroxene + olivine + amphibole assemblages at 0.5-1 GPa and temperatures of 1175-1350°C (Médard et al, 2004(Médard et al, , 2006. Such assemblages are observed as parts of exposed old arc ultramafic/ mafic cumulate complexes in the Talkeetna area, Alaska (DeBari and Coleman, 1989;DeBari and Sleep, 1991;Kelemen et al, 2003), the Kohistan Terrane of North Pakistan (Khan et al, 1993;Miller and Christensen, 1994;Burg et al, 1998;Ringuette et al, 1999;Jagoutz et al, 2007), and the Ivrea Zone in North Italy (Mehnert, 1975;Rivalenti et al, 1984;Quick et al, 1994). These complexes have been interpreted to be remnants of magma chambers emplaced at the base of the crust, close to the upper mantle-lower crust transition.…”

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

“…As discussed by Jagoutz and Schmidt (2013), a number of field, petrological and geochemical Jagoutz et al 2006Jagoutz et al , 2007 observations are not in accordance with this interpretation, and the interested reader is referred to these publications for an in-depth discussion. Based on these observations, we modeled Group 2 granitoids using the fractionation model of Jagoutz (2010) for Group 1 granitoids but included 10 % of garnetite instead of hornblendite to reproduce the trace element systematic of Group 2 granitoids (Fig.…”

“…Right side The viscosity versus SiO 2 of the experimental and modeled liquids. The viscosity difference in derivative melts of a hydrous and anhydrous fractionation sequence becomes significant around 1,000-1,050°C corresponding to *52-55 wt% SiO 2 true melt compositions (Jagoutz et al , 2007. Consequently, the garnet-and hornblende-gabbros of the hydrous fractionation line are generally cumulative and do not correspond to true liquid compositions.…”

“…(2) The mafic/ultramafic Chilas Complex, which is dominated by homogenous gabbronorites with minor associated dunites, pyroxenites, anorthosites and troctolites. These rocks were emplaced during intra-arc rifting and associated decompression melting in the subarc mantle at *85 Ma Jagoutz et al 2006;Jagoutz et al 2007;Khan et al 1989;Schaltegger et al 2002). (3) The Southern Plutonic Complex (SPC), which includes the Jijal ultramafics composed of dunites, wehrlites, pyroxenites and hornblendites/garnetites overlain by garnet-(meta)gabbros and diorites, the Sarangar gabbro and Kiru intrusive sequence, which, in turn, is overlain by the Kamilla amphibolites (Burg et al 2005).…”