General characteristics and tectonic attributes of the metamorphic volcanic rocks from the Rola Kangri Group Complex,northern Xizang

Much attention has long been drawn to the Rola Kangri Group Complex in northern Xizang for its tectonic setting in the southern part of the Lazhuglung-Jinshajiang suture zone.The 1∶250 000 geological survey in Baitoushan,Ganggairi and Shitoushan within the study area in 2004 has disclosed that the Rola Kangri Group Complex is composed of a suite of metamorphic intermediate-basic volcanic rocks intercalated with slices and/or masses of marble,metamorphic sandstone and slate,siliceous rocks and ultrabasic rocks.These rocks are all characteristic of oceanic-island,oceanic-ridge and island-arc volcanic rocks,including arc volcanic slices dominated by island-arc volcanic rocks in western Baitoushan;ophiolitic mélange slices dominated by oceanic-ridge metamorphic basalt intercalated with siliceous rocks and ultrabasic rocks in Ganggairi,and oceanic seamount slices dominated by oceanic-island volcanic rocks intercalated with carbonate rocks in Baitoushan and Shitoushan.It can be seen that the Rola Kangri Group Complex should be considered as the tectonic mélanges dominated by the volcanic rocks associated with marble,siliceous rocks and ultrabasic rocks formed in the oceanic,oceanic-island and continental-margin island-arc environments,and totally in the archipelagic arc-basin systems.