Detrital zircon record of Paleozoic and Mesozoic meta-sedimentary strata in the eastern part of the Baoshan block: Implications of their provenance and the tectonic evolution of the southeastern margin of the Tibetan plateau

摘要

The Baoshan block is one of the important members in the southeastern margin of the Tibetan Plateau. Cambrian to Jurassic (meta-) sedimentary strata and their metamorphic counterparts were well preserved in the eastern part of the Baoshan block. Zircon U-Pb dating, trace elements, and Hf isotope data for both the Cambrian to Jurassic (meta-) sedimentary sequences and the Lincang granite were used to deduce the provenance of sediments and crustal affinity with eastern Gondwanaland. The Lincang granite outcropped in the Fengqing area is typical S-type, with crystallization age of similar to 230 Ma and narrow range of zircon epsilon(Hf)(t) values from -15.5 to -10. Detrital zircons from Paleozoic strata range in age from Archean to early Paleozoic, with age peaks at similar to 2.5, similar to 0.95, and similar to 0.6 Ga. Triassic age peak (similar to 230 Ma) was also detected in the Jurassic strata. Detrital zircon epsilon(Hf)(t) values exhibit a wide range from negative to positive for each of the four major age groups, showing the host magma of zircons from these groups have diverse sources. The Baoshan block should be along the Indian margin as the Qiangtang, Tengchong and Simao-Indochina blocks in Early Paleozoic based on the provenance analyses. Sediment inputs eroded from both the Lincang granite and the coeval igneous rocks in the Baoshan and Gongshan blocks were the dominant contributions to the Jurassic strata after the amalgation of the Baoshan and Simao-Indochina blocks. Tectonic processes linking dispersion of the Baoshan-Sibumasu terrane from the Gondwana supercontinent to the collision with the Simao-Indochina block and the deposition of the Cambrian to Jurassic sedimentary sequences were reconstructed. (c) 2015 Elsevier B.V. All rights reserved.