西藏雅鲁藏布江缝合带中段仁布豆荚状铬铁矿成因及构造意义

藏南雅鲁藏布江缝合带为目前国内铬铁矿储量最大的缝合带.本文报道了缝合带中段仁布蛇绿岩的豆荚状铬铁矿床,围绕矿床特征开展成因探讨,对缝合带的形成演化和成矿作用提供新制约.仁布蛇绿岩呈近东西走向带状产出,主要由近30个大小不等的地幔橄榄岩体组成.地幔橄榄岩体主要为经历不同程度蛇纹石化的方辉橄榄岩和少量纯橄岩.在纯橄岩和方辉...     

Paleogene island arc collision-related conglomerates, Yarlung–Tsangpo suture zone, Tibet

Coarse clastic rocks in the Liuqu Conglomerate, formed in both terrestrial and subaqueous settings, record a Paleogene phase in the tectonic evolution of Tibet. Facies changes are commonly abrupt with rapid changes in clast types, grain size and stratal patterns. Sediments were derived from the leading (northern) edge of the Indian margin and a Late Jurassic–Cretaceous intraoceanic island arc that lay within Tethys. The coarse clastic sedimentary rocks of the Liuqu conglomerates are extremely proximal, but are locally offset relative to their original source terranes. They record aspects of the history of collision between these terranes and are interpreted to have been deposited in oblique–slip basins that developed along the zone of collision. The absence of clasts derived from terranes to the north of the Yarlung–Tsangpo suture suggests that basins associated with deposition of the Liuqu Conglomerate developed prior to the final collision between India and Asia.     

The Gangdese thrust: a phantom structure that did not raise Tibet

Detailed field investigations do not support the existence of a ‘Gangdese thrust’ along the Yarlung Tsangpo suture zone in southern Tibet. A relationship where Lhasa terrane rocks are thrust southwards over components of this zone was not observed over 2000 km of the suture. On the contrary, at the type locality of this ‘Gangdese thrust’, Miocene conglomerates unconformably overlie an eroded surface of Lhasa terrane rocks. Interpretations that invoke Late Oligocene – Early Miocene south‐directed thrusting on a ‘Gangdese thrust’ as a mechanism for uplift of the Tibetan Plateau must therefore be reassessed.     

OCEANIC DEPOSITS IN THE YARLUNG—TSANGPO SUTURE ZONE: STRUCTURAL SETTING, RADIOLARIAN AGES AND THEIR TECTONIC IMPLICATIONS

OCEANIC DEPOSITS IN THE YARLUNG—TSANGPO SUTURE ZONE: STRUCTURAL SETTING, RADIOLARIAN AGES AND THEIR TECTONIC IMPLICATIONS