Аннотация:Located in the southwestern Qinling Mountains of central China near the northern margin of the yangtze plate, the Bikou terrane has long been controversial regarding how it relates to the Late Precambrian tectonic history of the yangtze plate. The igneous and sedimentary succession of the Bikou terrane has been variously interpreted to represent either a Meso-Neoproterozoic rift assemblage, or a subduction arc assemblage. Our recent work involving igneous petrologygeochemistrysedimentary basin analysis strongly supports the subduction arc interpretation. In addition, SHRIMP U-Pb zircon dating of volcanic rocks from the Bikou arc reveal that subduction occurred along the northern margin of the yangtze plate in the Neoproterozoic, ~846-776 Ma. Additionallynew 40Ar/39Ar and SHRIMP U-Pb ages of mafic dike swarms in the Bikou arc indicate emplacement occurred in the Late Neoproterozoic, ~689-660 Ma. Therefore the age of volcanism is coincident with, and thus incompatible with, previously proposed extension-related mantle upwelling and break-up of Rodinia involving the South China Block (SCB). We propose that the yangtze plate collided with the Cathaysian Block at the end of the Grenville orogeny to form the SCB, and subsequently developed a long-lived subduction-related arc along its northern margin in the Neoproterozoic, ~846-776 Ma. Subsequent rifting that formed the passive margin of the SCB may have been initiated ~689-660 Ma.
