地幔内超高压矿物的爆炸

在西藏雅鲁藏布江缝合带的蛇绿岩的豆荚状铬铁矿中,首次发现硅酸盐包裹体具有爆炸结构.在矿石薄片中普遍见到这种高能硅酸盐包体的爆炸结构.在爆炸结构中,铬尖晶石被炸落成不规律的显微碎块,具有尖锐棱角,碎块大小不一,堆积在硅酸盐包体内.此外,许多张性显微裂隙围绕爆炸的硅酸盐包体呈蛛网状分布.推断爆炸前的原生矿物是含水的镁硅酸盐和镁铝硅酸盐矿物.当这种高能级的超高压含水矿物受地幔柱带动超过水线”时发生爆炸和放水作用,同时产生地震.

Explosion of Ultrahigh Pressure Minerals in the Mantle

The microexplosion structure (cobweb structure) of ultrahigh pressure minerals was found for the first time in podiform chromitites within the mantle peridotite facies of Luobusa ophiolite along the Yarlung Zangbo suture zone. The explosion structures of high-energy silicate inclusions are commonly seen in thin sections. In explosion structure, chrome-spinel fragments are irregularly scattered in silicate minerals. With sharp edges and highly varied sizes, they are very unevenly distributed, showing distinct extention micro-brecciated structure. In addition, there are many tensional microfractures around the explosion silicate inclusions. It is inferred that, before explosion, the primary mantle minerals were hydrous magnesium silicate or magnesium-aluminium silicates. When such high-energy phase rose and passed the water line as a result of the action of mantle plume, explosion took place, accompanied by the release of water. The upward migration of large-sized high energy hydrous minerals may lead to deep-focus earthequakes.