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对位于雅鲁藏布江缝合带西段北亚带错不扎地幔橄榄岩铂族元素地球化学特征进行研究,旨在对其岩石成因和构造环境进行限定。错不扎地幔橄榄岩以方辉橄榄岩和含单辉方辉橄榄岩为主。含单辉方辉橄榄岩具有较高的铂族元素(PGEs)含量,w(PGEs)=22.31×10~(-9)~36.12×10~(-9),平均值为29.60×10~(-9),高于原始地幔含量;而方辉橄榄岩的w(PGEs)处于17.34×10~(-9)~25.18×10~(-9)之间,平均值为21.08×10~(-9),略低于原始地幔值。相对岩浆成因超基性岩,两岩类皆强烈富Os和Ir,为部分熔融后残余的地幔体。含单辉-方辉橄榄岩及部分方辉橄榄岩含较高的Pd,(Pd/Ir)m比值远大于1,具左倾型PGE组成模式,而且两者都具有低于原始地幔的Cu/Pd比值。综合研究表明错不扎方辉橄榄岩是熔融程度较低的含单辉-方辉橄榄岩继续部分熔融后的残余;两者在部分熔融过程中可能存在部分赋存Pd的硫化物未完全溶解进入硅酸盐熔体,此后又受到俯冲带岩浆渗滤形成的富硫化物熔体的改造。
The geochemical characteristics of the platinum group elements in the northern subboundary zone of the Brahmaputra suture zone in the northern part of the Brahmaputra suture zone are studied in order to limit the genesis and tectonic setting of the rocks. The faultless mantle peridotite is mainly composed of halloysite and mono-hullite. Hg-bearing peridotites have higher content of PGEs, ranging from 22.31 × 10 -9 to 36.12 × 10 -9, with an average of 29.60 × 10 ~ (-9) -9), which is higher than the original mantle content. However, the w (PGEs) of the harzburgites range from 17.34 × 10 -9 to 25.18 × 10 -9 with an average of 21.08 × 10 ~ 9), slightly lower than the original mantle value. Relative to the magmatic origin of ultrabasic rocks, the two rocks are strongly rich in Os and Ir, which are partially remnant mantle bodies. The ratios of Pd / (Pd / Ir) m with mono-humateite and hectorite are much higher than 1 and have a leftward PGE composition pattern, and both have lower ratios of Cu / Pd ratio. The comprehensive study shows that the fault-free karst liguolites are the remnants of partially melted single-hullite-harzburgites that remain partially melted. During the partial melting, both may partially dissolve Pd-bearing sulphides Into the silicate melt, and later rebuilt by the sulfide-rich melt formed by subduction magmatic diafiltration.