ABSTRACT

Diopside-rich rocks (diopsidites) are interlaminated with nephrite in boulders derived from metasomatic contacts developed between Pounamu Ultramafic meta-serpentinite and country rock Alpine Schist, Westland, New Zealand. Petrographic textures indicate that parental tremolite rock, formed by metasomatic diffusion during metamorphism, has been intensely deformed and recrystallised to alternating semi-nephrite and nephrite domains during development of a secondary crenulation cleavage. Nephrites are subsequently sequentially overprinted by porphyroblastic tremolite, diopside, then further tremolite. Crystallisation is controlled by fluctuating activities of SiO₂, CaO and H₂O in associated fluids. Pervasive dissolution of nephritic tremolite and crystallisation of diopside generates diopsidites containing accessory epidote, uvarovite and zincian chromite formed in equilibrium with H₂O-rich fluids. Diopsidites are in turn overgrown by coarse grained (in places > 50 cm long) diopside crystals, interpreted to have infilled an extension fracture that formed during ongoing uplift of the Southern Alps.

摘要

富含透辉石的岩石（透辉石）与软玉夹层在巨石中，这些巨石源自新西兰韦斯特兰的 Pounamu 超基性变蛇纹岩和围岩阿尔卑斯片岩之间形成的交代接触。岩相结构表明，在变质过程中通过交代扩散形成的母体透闪石岩石在二次细缝解理的发展过程中已经强烈变形并重结晶成交替的半软玉和软玉区域。软玉随后依次被斑晶透闪石、透辉石和其他透闪石叠印。_{结晶由 SiO 2}、CaO 和 H ₂的波动活性控制O 在相关的流体中。_{软闪石透闪石的普遍溶解和透辉石的结晶生成含有副绿帘石的透辉石、钙钛矿和与富含 H 2} O 的流体平衡形成的锌亚铬铁矿。透辉石又长满了粗粒（在大于 50 厘米长的地方）透辉石晶体，解释为填充了在南阿尔卑斯山持续隆升过程中形成的延伸裂缝。