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帮果日—波库蛇绿岩带位于雅鲁藏布江缝合带的最西段,由帮果日蛇绿岩和波库混杂岩构成,呈北西展布,长128 km,宽5~10 km。帮果日蛇绿岩由方辉橄榄岩和二辉橄榄岩构成,岩石由橄榄石(Fo=85.2~88.0,平均86.6)、顽火辉石(Mg#=89.3~94.3,平均91.2)、透辉石(Mg#=92.0~94.9,平均93.1)构成,以高铝(Al2O3=0.96%~2.10%)、高钛(Ti=173~261μg/g)为特征,微量元素含量与MOR地幔岩的接近,亏损REE,ΣREE仅为球粒陨石的33%~71%,估算其为原始地幔经过6%~12%部分熔融的产物。波库混杂岩基质由板岩、粉砂质板岩构成,岩块有橄榄岩、辉长岩、硅质岩、砂岩、灰岩等。通过对帮果日蛇绿岩同位素测年结果、波库混杂岩之中硅质岩岩块放射虫化石的研究,确定帮果日—波库蛇绿岩带形成于晚白垩世,是新特提斯洋俯冲消减的产物;帮果日蛇绿岩代表了新特提斯洋洋壳的残留,属典型的MOR型蛇绿岩。
Fruit Day - The Po Kuo ophiolite belt is located in the westernmost segment of the Yarlung Zangbo suture zone, consisting of the Binguori ophiolite and the Boqu melange, and is northwest of Guangxi with a length of 128 km and a width of 5-10 km. Pyongyang ophiolite is composed of hectorite and lherzolite. The rocks are composed of olivine (Fo = 85.2-88.0, average 86.6), enstatite (Mg # = 89.3-94.3, average 91.2) The results show that the trace element contents of high-alumina (Al2O3 = 0.96% -2.10%) and high-titanium (Ti = 173-261μg / g) Close to the loss of REE, ΣREE only chondrite 33% ~ 71%, estimated that the original mantle after 6% to 12% of the partial melting of the product. The basalt mélanges consist of slate and silty slate with peridotite, gabbro, silicalite, sandstone and limestone. Based on the results of the isotopic dating of the ophiolite greens and the radiolarian fossils from the siliceous rocks in the Boqu mélanges, it is confirmed that the Sinogreen-Pooch ophiolite zone was formed in the Late Cretaceous The Tethyan subducted the product of the subduction; the Bingguo ophiolite represented the residual of the Neo-Tethyan oceanic crust, and is a typical MOR-type ophiolite.