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The Altaids of Central Asia: A tectonic and evolutionary innovative review

The assembly of Rodinia: The correlation of early Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB)

Final amalgamation of the Tianshan and Junggar orogenic collage in the southwestern Central Asian Orogenic Belt: Constraints on the closure of the Paleo-Asian Ocean

The Tarim Craton, located in the center of Asia, was involved in the assembly and breakup of the Rodinia supercontinent during the Neoproterozoic and the subduction-accretion of the Central Asian Orogenic Belt (CAOB) during the Paleozoic. However, its tectonic evolution during these events is controversial, and a link between the Neoproterozoic and Paleozoic tectonic processes is missing. Here we present zircon U-Pb ages, Hf isotopes, and whole-rock geochemical data for the extensive granitoids in the western Kuruktag area, northeastern Tarim Craton. Three distinct periods of granitoid magmatism are evident: circa 830–820 Ma, 660–630 Ma, and 420–400 Ma. The magma sources, melting conditions (pressure, temperature, and water availability), and tectonic settings of various granitoids from each period are determined. Based on our results and the geological, geochronological, geochemical, and isotopic data from adjacent areas, a long-lived accretionary orogenic model is proposed. This model involves an early phase (circa 950–780 Ma) of southward advancing accretion from the Tianshan to northern Tarim and a late phase (circa 780–600 Ma) of northward retreating accretion, followed by back-arc opening and subsequent bidirectional subduction (circa 460–400 Ma) of a composite back-arc basin (i.e., the South Tianshan Ocean). Our model highlights a long-lived accretionary history of the southwestern CAOB, which may have initiated as part of the circum-Rodinia subduction zone and was comparable with events occurring at the southern margin of the Siberian Craton, thus challenging the traditional southward migrating accretionary models for the CAOB.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2013TC003501

Neoproterozoic to Paleozoic long‐lived accretionary orogeny in the northern Tarim Craton

Large-scale porphyry-type mineralization in the Central Asian metallogenic domain: A review

Numerous lenses of eclogite occur in a belt of augen orthogneisses in the Gubaoquan area in the southern Beishan orogen, an eastern extension of the Tianshan orogen. With detailed petrological data and phase relations, modelled in the system NCFMASHTO with THERMOCALC, a quantitative P-T path was estimated and defined a clockwise P-T path that showed a near isothermal decompression from eclogite facies (>15.5 kbar, 700-800 � C, omphacite + garnet) to high-pressure granulite facies (12-14 kbar, 700-750 � C, clinopyroxene + sodic plagioclase symplectitic intergrowths around ompha- cite), low-pressure granulite facies (8-9.5 kbar, 700 � C, orthopyroxene + clinopyroxene + plagio- clase symplectites and coronas surrounding garnet) and amphibolite facies (5-7 kbar, 600-700 � C, hornblende + plagioclase symplectites). The major and trace elements and Sm-Nd isotopic data suggest that most of the Beishan eclogite samples had a protolith of oceanic crust with geochemical characteristics of an enriched or normal mid-ocean ridge basalt. The U-Pb dating of the Beishan eclogites indicates an Ordovician age of c. 467 Ma for the eclogite facies metamorphism. An 39 Ar ⁄ 40 Ar age of c. 430 Ma for biotite from the augen gneiss corresponds to the time of retrograde metamorphism. The combined data from geological setting, bulk composition, clockwise P-T path and geochronology support a model in which the Beishan eclogites started as oceanic crust in the Palaeoasian Ocean, which was subducted to eclogite depths in the Ordovician and exhumed in the Silurian. The eclogite-bearing gneiss belt marks the position of a high-pressure Ordovician suture zone, and the calculated clockwise P-T path defines the progression from subduction to exhumation.

C. M. Han

Papers

Ordovician eclogites from the Chinese Beishan: implications for the tectonic evolution of the southern Altaids