Publikationsdatum:
2014-02-26
Beschreibung:
ABSTRACT [1] 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: ca. 830 – 820 Ma, 660 – 630 Ma and 420 – 400 Ma. The ca. 830 - 820 Ma granitoids are dominantly sodic, I-types with negative ɛ Hf values and abundant inherited zircons, implying fluid-present partial melting of Archean mafic lower crust. The ca. 660 – 630 Ma and ca. 420 - 400 Ma granitoids show large variations in zircon Hf isotopic compositions likely due to magma mixing between juvenile and ancient materials with different compositions and melting conditions. Based on our results and the geochronological, geochemical and isotopic data from adjacent areas, a long-lived accretionary orogenic model is proposed. This model involves an early phase (ca. 950 – 780 Ma) of southward advancing accretion from the Tianshan to northern Tarim and a late phase (ca. 780 - 600 Ma) of northward retreating accretion, followed by back-arc opening and subsequent bidirectional subduction (ca. 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.
Print ISSN:
0278-7407
Digitale ISSN:
1944-9194
Thema:
Geologie und Paläontologie
Permalink