COMPOSITION, AGE OF DETRITAL ZIRCON, AND PROVENANCE OF THE TUFF-TURBIDITE SEQUENCE IN THE DZHIDA ZONE (Central Asian Fold Belt)
A.L. Elbaev1, I.V. Gordienko1, V.B. Khubanov2, M.S. Skripnikov1, D.E. Yudin1, A.M. Khubanov2
1Dobretsov Geological Institute, Siberian Branch of Russian Academy of Sciences, Ulan-Ude, Russia
2Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
Keywords: Forearc basin, detrital zircon dating, sedimentary provenance, Dzhida Island paleoarc, Southwestern Transbaikalia
Abstract
We analyze the composition of : rocks and provide age estimates for detrital zircon grains extracted from sandstones of the tuff-turbidite sequence in the Dzhida Zone of the Central Asian Fold Belt. The sandstones are classified as feldspathic graywackes based on their mineralogical and petrochemical characteristics and are interpreted as first-cycle sediments. The detrital material consists predominantly of volcanic rock fragments, with plagioclase grains being subordinate. Relatively low values of the chemical index of alteration (CIA = 58-68) indicate moderate to weak chemical weathering of lithic components. This reflects the low maturity of the detrital material, which was derived primarily through mechanical breakdown of source rocks. The U-Pb age distribution for detrital zircons from the tuff-turbidite sandstones is bimodal, with major peaks at 530 and 510 Ma. No Neoproterozoic zircon grains were identified in the samples studied. The graywacke composition, low sediment maturity, and the observed U-Pb age distribution of detrital zircons collectively suggest that these deposits accumulated in a forearc basin setting, with detritus supplied from local sources - namely, Early Cambrian volcanic rocks of the Dzhida ensimatic island arc.
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