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The Ghorveh batholith, located in the central part of the Sanandaj–Sirjan Zone (SSZ), Iran, preserves several sequences of Mesozoic plutonic and volcanic rocks. This study presents systematic analyses of the calc‐alkaline granites and monzodiorites from the southern part of the Ghorveh pluton. The granites are metaluminous to slightly peraluminous with A/CNK ratios of 0.97–1.02, indicating an A‐type granitic affinity. High Rb, Th, and K and low Sr, P, and Ti concentrations indicate an involvement of crustal materials. Whole‐rock negative εNd(t) values and relatively high TDM1 model ages support a continental crustal source. Thus, the granites are of fractionated A‐type in composition produced by partial melting of crustal materials. The monzodiorites have incompatible trace element patterns with enrichment in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) relative to heavy rare earth elements and high‐field strength elements. This combined with the high Mg# values and the positive εNd and εHf(t) values, indicate a mantle‐derived origin. Dating results show that the granites and monzodiorites have uniform crystallization ages of ~150 Ma. Previous results and our new data suggest that the Jurassic subduction of Neo‐Tethyan Oceanic crust under the Eurasian continent was followed by slab rollback that induced back‐arc extension. Heat transfer from arc magmas increased the degree of decompressional melting in the thinned lithosphere. Melting of the presumably homogeneous crust was concurrent with emplacement of the intermediate composition magmas. Consequently, we propose that the Ghorveh area of the central SSZ developed in a supra‐subduction extensional phase during the Late Jurassic. [ABSTRACT FROM AUTHOR]

A newly defined, 250 km by 500 km, Carboniferous-Triassic subduction-accretion complex, the Mazar accretionary prism in the western Kunlun, comprises two subduction complexes and a forearc-basin succession. (1) The Bazar Dara subduction complex contains imbricated blocks of sandstone, arenite, limestone, and metavolcanic rocks in a matrix of weakly metamorphosed Triassic deep-sea turbidites. The metavolcanic rocks include basalt, diabase, spilite, and andesitic porphyry. Trace element geochemistry shows that pillow and amygdaloidal basalts are oceanic-island tholeiites. This zone has Ordovician to Permian fossils and is situated on the older, more highly deformed and metamorphosed side of the prism adjacent to the Sailiyak magmatic arc. (2) The Heweitan subduction complex is composed of blocks of limestone, turbidite, and radiolarite in a slate-phyllite matrix intercalated with calc-aikalic volcanic rocks. This complex has Permian to Triassic fossils and is situated on the younger, less deformed, and metamorphosed side of the prism adjacent to the suture zone. (3) The Qitai forearc basins are infilled with turbidites (Late Triassic) intercalated with carbonates; these rocks overlie the accretionary prism. The accretion-related structure is dominated by large-scale northeast-dipping thrusts and subvertical cleavage stitched by 215-190 Ma granites. There is an overall decrease in metamorphic grade and deformation intensity from the arc to the suture zone across the Bazar Dara and Heweitan subduction complexes. The Mazar accretionary prism formed by subduction-accretion processes during closure of the Paleotethyan Ocean and the final docking of the Gondwanan Karakoram-Qiangtang block to the Cathaysian (Eurasian) Kunlun block. Keywords: western Kunlun, accretionary prism, subduction, accretion, arc.

A study of the tectonic units in the Eastern Tianshan collage of the Central Asian Orogenic Belt in China is made. An analysis is also made on the Paleozoic geological history of the archipelago located between the Tarim and south Angaran continental margin.