日照胡家岭石榴单辉辉石岩体的地球化学特征及其成因  

Geochemical characteristics of garnet clinopyroxenite at Hujialing,Rizhao,and their bearing on petrogenesis

作　　者：李天福[1] 杨经绥[1] 

机构地区：[1]国土资源部大陆动力学重点实验室,中国地质科学院地质研究所,北京100037

出　　处：《岩石矿物学杂志》2005年第5期469-475,共7页Acta Petrologica et Mineralogica

基　　金：国土资源部基础项目(2001CCB00900);973专项(2003CB716500);国家自然科学基金重大项目(40399140)

摘　　要：与原始地幔相比,苏鲁超高压变质带的日照胡家岭石榴单辉辉石岩体全岩化学成分易熔组分均较高,而难熔组分均较低,全岩的SiO2含量为44.04%～50.50%,高MgO(12.77%～18.73%),高CaO/Al2O3(1.6～8.0),低碱,Mg#的变化范围为74.82～86.13,成分特点类似铝亏损型科马提岩.稀土元素配分型式为典型的单斜辉石稀土元素配分型式,重稀土元素相对亏损,(Gd/Yb)N=3.51～5.87.铂族元素的总体丰度为19.18×10-9～59.44×10-9,变化范围较大,高于地幔橄榄岩的丰度,(Pd/Ir)N具有8.58～11.07的正斜率.这些特点表明形成石榴单辉辉石岩的岩浆为地幔源区残留石榴石、主要熔出单斜辉石的高程度部分熔融的产物,折返前可能由单斜辉石+石榴石相组成.铂族元素丰度高、正斜率的特点表明其分布受到了地幔高程度部分熔融的控制且没有硫化物的分离,说明熔浆中硫是不饱和的.Bulk rock chemistry of Hujialing garnet clinopyroxenite in Rizhao of the Sulu ultrahigh-pressure metamorphic belt is rich in fusible composition and low in refractory composition when compared with that of the primary mantle. Whole rock has 44.04 % - 50.50 % SlOe, high MgO（ 12.77 % - 18.73 % ）, high CaO/Al2O3 （ 1.6 - 8.0 ）, low alkali and Mg^# （74.82 - 86.13 ）, which shows that the rock has an affinity to alumina-depleted komatiite. The REE partition pattern has the form of clinopyroxne and relative HREE depletion with （Gd/Yb）N being 3.51-5.87, The total PGE concentration varies in a wide range of 19.18 × 10^9 -59.44 × 10^9 and is higher than that of xenolith and Alpine type peridotites with （Pd/Ir）N of 8.58- 11.07, All of these characteristics indic, ate that the magma which produced the garnet clinopyroxenite was formed mainly by melting of the clinopyroxene from the mantle source with residual garnet, The phases of the rock before exhumation might have been clinopyroxene ＋ garnet. The high concentration and positive slope of PGE suggest that their distribution was controlled by a high degree of partial melting and that magma was sulfur-unsaturated without sulfide segregation.

关 键 词：石榴单辉辉石岩 地球化学 部分熔融 铂族元素 胡家岭 日照 

分 类 号：P588.125[天文地球—岩石学] P59[天文地球—地质学]