A REVIEW OF EARLY PERMIAN (300–270 MA) MAGMATISM IN EASTERN KAZAKHSTAN AND IMPLICATIONS FOR PLATE TECTONICS AND PLUME INTERPLAY

The history of the Central Asian Orogenic Belt (CAOB) was marked by several major events of magmatism which produced large volumes of volcanic and intrusive (mafic-ultramafic and granitic) rocks within a relatively short time span (30–40 Ma) over a vast area. The magmatic activity postdated the orogenic stages of accretionary-collisional belts in Central Asia and likely resulted from the impact of mantle plumes that formed Large Igneous Provinces (LIPs). The formation of the Tarim–South Mongolia LIP at 300–270 Ma is the best known among the major Permian events of basaltic and granitic magmatism. Early Permian igneous rocks (volcanic, subvolcanic and intrusive suites that vary from ultramafic to felsic compositions) of the same age range (300 to 270 Ma) have been recently found also in Eastern Kazakhstan, within the late Paleozoic Altai collisional system. The compositions and ages of the rocks suggest that the Eastern Kazakhstan magmatism was the northward expansion of the Tarim LIP. The spread of the Tarim LIP was apparently facilitated by lithospheric extension after the Siberia-Kazakhstan collision. The extension led to rheological weakening of the lithosphere whereby deep mantle melts could penetrate to shallower depths. The early Permian history of Eastern Kazakhstan was controlled by the interplay of plate tectonic and plume processes: plate-tectonic accretion and collision formed the structural framework, and the Tarim mantle plume was a heat source maintaining voluminous magma generation