滇西北澜沧江结合带的边界断裂和主要特征

澜沧江结合带的东、西边界断裂分别为位于澜沧江西岸的吉岔断裂和位于碧罗雪山主峰的碧罗雪山断裂.澜沧江结合带由上古生界吉东龙组（P₁j）、沙木组（P₂sm）组成，形成于浅海陆棚-陆棚边缘盆地环境.其中，沙木组上段（P₂sm²）的火山岩形成于岛弧环境.沿吉岔断裂出露的超镁铁-镁铁岩划分为2个部分：吉岔超镁铁-镁铁-斜长花岗岩具蛇绿岩特征，很可能属澜沧江洋壳的零星残片，在澜沧江洋消亡过程（早中三叠世?）中迁移定位；维登镁铁岩属阿拉斯加型，是兰坪-思茅中生代沉积盆地消亡过程（白垩纪）中沿吉岔断裂上侵的产物.

BOUNDARY FAULTS AND MAIN CHARACTERISTICS OF THE LANCANG RIVER SUTURE ZONE IN NORTHWEST YUNNAN

The eastern and western boundary faults of Lancang River suture zone are respectively Jicha Fault located on the west bank of Lancang River and Biluo Xueshan Fault along the main peak of Bilou Mt. The suture zone, consisting of the Upper Paleozoic Jidonglong and Shamu formations, is formed in the neritic shelf-shelf marginal basin environment, among which the volcanic rocks of upper member, Shamu Formation (P₂sm²) are formed in island-arc setting. The ultramafic-mafic rocks outcropped along Jicha Fault can be divided into two parts:One is Jicha ultramafic-mafic-plagiogranite with the characteristics of ophiolite, probably the fragmentary remnants of Lancangjiang oceanic crust, migrated and emplaced with the extinction of Lancangjiang Ocean (Early-Middle Triassic?); The other is Weideng mafic rocks, belonging to the Alaskan-type, intruding upward along the Jicha Fault during the subduction of the Mesozoic Lanping-Simao sedimentary basin in Cretaceous period.