滇西南曼信夭折堆积岩的确认及其意义

CONFIRM AND SIGNIFICANCE OF FAILED ACCUMULATIVE ROCK IN MANXIN,SOUTHWESTERN YUNNAN

产于滇西南孟连曼信的苦橄岩，前人定为苦橄玢岩岩脉。经研究发现该苦橄岩普遍发育堆积结构，同时又普遍发育枕状构造且基质具淬火结构，并且与石炭纪洋脊型—准洋脊型玄武岩具有成因演化关系。这表明该苦橄岩不是岩脉，而是水下喷出相的夭折堆积岩，是因洋底扩张速度改变而导致岩浆房状态改变的结果，这也为澜沧江洋的扩张作用提供了佐证。

There is one kind of picrite in Manxin of Menglian of Southwestern Yunnan that was considered as vein of picrite porphyrite by predecessors.Authors have finished full and accurate field work,identified lots of sections and studied geochemical natures for the picrite.It is discovered that there is accumulative texture in the picrite,and there are pillow structure and quenching texture in the same picrite.There is relationship of evolution between the picrite and MORB or MORB like in Carbonic.These facts show that the picrite is not vein but is failed accumulative rock of underwater eruption,which was resulted from the state change of magma chamber with the change of oceanic floor spreading rate,and supported the oceanic floor spreading of Lancangjiang Ocean.