743±17 MA GRANITE CLAST FROM JURASSIC CONGLOMERATE, KAMIASO, MINO TERRANE, JAPAN: THE CASE FOR SOUTH CHINA CRATON PROVENANCE (KOREAN GYEONGGI BLOCK?)

Abstract

The polymict Kamiaso Conglomerate (Mino Terrane, Japan) contains Jurassic to Palaeoproterozoic clasts-probably derived from Korean basement that lay nearby to the northwest at time of deposition. Clast K2 broke cleanly into two halves during sampling (but the halves were recombined for zircon separation). A third of the K2 zircons are colourless euhedral prisms with oscillatory zoning, with no inheritance and yielded a SHRIMP U/Pb date of 743±17 Ma. Two thirds of K2 zircons are brown oscillatory-zoned corroded prisms with a date of 1860±8 Ma, with inherited cores up to ~2460 Ma. A likely explanation for this could be that clast K2 might have been composite, and contained undistinguished 743 Ma and 1860 Ma granites. Kamiaso granitic clast K3 igneous zircons gave a date of 179.3/-2.1 Ma (Toarcian-Early Jurassic), with 2100-2300 Ma and ~1860 Ma inherited cores. ~740 Ma A-type magmatism related to the extension and break up of Rodinia occurs in both Korea (Gyeonggi Block) and the main part of the South China Craton, but is unknown in the Sino-Korean Craton. Thus from recognition of a 743 Ma clast, the Kamiaso detritus was probably derived from the northernmost part of the South China Craton in Korea. © 2004 Elsevier Ltd. All rights reserved.