| “三江”义敦岛弧带玄武岩喷发序列与裂谷—岛弧转化 |
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| THE ERUPTION SEQUENCES OF BASALTS IN THE YIDUN ISLAND-ARC, SANJIANG REGION AND EVOLUTION OF RIFT TO ISLAND-ARC |
| There were two of cycles of basaltic volcanism in the early stage of formation of the Yidum Island-Arc: Genlong cycle and Gacun(Xiacun)cycle. The Genlong cycle may be divided into three subcycles: Nalenghai, Genlong and Chizhong subcycles. The rock suites in the Nalenghai subcycle include a basalt-rhyolite bimodal suite and basaltic rocks, which constitute an alkaline basaltic magma series. The basalts are geochemically characteristic of continent rift basalt. The center of volcanism in the Genlong subcycle moved from both sides to the central part, with the rock series changing from the alkaline series to the tholeiitic one.Petrological and geochemical studies show that the basaltic rocks are geochemically transional and have a trendency of evolution of rift basalts to seafloor basalts. The rocks of the Chizhong subcycle consists of pillowmassive tholeiitic basalts and boninites.The pillow basalts, formed in the early stage of basaltic volcanism, are transitional whereas the massive basalts in the later stage are more familiarized with typical island-arc tholeiitic basalts. The volcanic rocks of the Gacun cycle consist of basalt-andesite-dacite, which belong to the calc-alkaline series. The rocks are typical island-arc volcanics.A petrological model on the early-stage evolution of the Yidun Island-Arc is suggested on the base of studies on rock association, temporal-spacial distribution, petrology and geochemostry of basalt sequences. The evolution history is divided into three stages; 1) fromation of a horse-graben system of rift on continental margin; 2) evolution of the rift to an island-arc through back-arc opening; 3) intense arc-forming volcanism. |
| HOU Zeng-qian,MO Xuan-xue,TAN Jing,HU Shi-hua,LOU Zai-wen.1993.THE ERUPTION SEQUENCES OF BASALTS IN THE YIDUN ISLAND-ARC, SANJIANG REGION AND EVOLUTION OF RIFT TO ISLAND-ARC[J].Acta Geoscientica Sinica,14(1):49-67. |
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