摘要
Chromite deposits in the Havana-Matanzas ophiolites of Western Cuba include both Al-([Cr/(Cr+Al)=0.44-0.46])and Cr-rich([Cr/(Cr+Al)=0.65-0.74]chromitites that commonly occur in the upper part of mantle ectonites near the mantle-crust transition zone.These chromitites generally form small lenticular bodies spatially associated with strongly serpentinized dunite.Platinum group minerals(PGM)are found only in the Cr-rich chromitites,as euhedral or subeuhedral,very small(less than 10μm long)crystals.The most abundant PGM is laurite,accompanied by minor osmium,cuproiridsite,iridium and an unnamed phase composed of Ir-Ni-Fe-S,all of which are magmatic in origin.These magmatic PGMs and amphiboles crystallized at high temperatures(~1300℃)and at relatively high sulphur fugacities from fluid-rich magmas.The chromite mineral chemistry suggests that melts that were in equilibrium with Cr-rich and Al-rich chromitites had island-arc tholeiite–boninite and backarc basin basalt(BABB)affinities,respectively.
基金
Spanish project(CGL2012-36263)that has been sponsored by the Ministerio de Economia y Competitividad.
