CAJ | 학술논문

达拉布特蛇绿岩中地幔橄榄岩的主体为方辉橄榄岩，含少量纯橄岩和二辉橄榄岩，岩石遭受强烈蚀变。方辉橄榄岩单斜辉石、斜方辉石、橄榄石和尖晶石的主量元素特征均显示从深海地幔橄榄岩向SSZ地幔橄榄岩过渡的特征，与斜方辉石原位LA-ICP-MS微量元素特征一致，二辉橄榄岩具有深海地幔岩的性质。采用尖晶石-橄榄石平衡氧逸度计算方法，得出方辉橄榄岩的Δlog (fo2) FMQ在-0.14至+0.96log FMQ之间，具有MOR地幔橄榄岩向SSZ地幔橄榄岩过渡的特点或弧后盆地至岛弧过渡的特征。尖晶石Ga-Ti-Fe3+#图解显示纯橄岩成因可能和地幔橄榄岩与岛弧拉斑玄武岩的反应有关，而方辉橄榄岩可能为地幔橄榄岩与MOR熔体反应以及SSZ环境中含水熔体反应后的残余。纯橄岩和方辉橄榄岩∑REE都低于球粒陨石，且具有LREE富集的U型稀土元素配分模式，暗示了岩石和流体/熔体之间的相互作用。综合以上研究表明，达拉布特蛇绿岩形成于弧后扩张脊并受俯冲流体/熔体影响。
체랍포특사록암중지만감람암적주체위방휘감람암，함소량순감암화이휘감람암，암석조수강렬식변。방휘감람암단사휘석、사방휘석、감람석화첨정석적주량원소특정균현시종심해지만감람암향SSZ지만감람암과도적특정，여사방휘석원위LA-ICP-MS미량원소특정일치，이휘감람암구유심해지만암적성질。채용첨정석-감람석평형양일도계산방법，득출방휘감람암적Δlog (fo2) FMQ재-0.14지+0.96log FMQ지간，구유MOR지만감람암향SSZ지만감람암과도적특점혹호후분지지도호과도적특정。첨정석Ga-Ti-Fe3+#도해현시순감암성인가능화지만감람암여도호랍반현무암적반응유관，이방휘감람암가능위지만감람암여MOR용체반응이급SSZ배경중함수용체반응후적잔여。순감암화방휘감람암∑REE도저우구립운석，차구유LREE부집적U형희토원소배분모식，암시료암석화류체/용체지간적상호작용。종합이상연구표명，체랍포특사록암형성우호후확장척병수부충류체/용체영향。
The peridotites in Darbute ophiolite consist mainly of harzburgite and minor dunite, lherzolite and dunite and exhibit strong alteration. The major elements of clinopyroxene, orthopyroxene, olivine and spinel of harzburgite show the characteristics of both abyssal peridotite and SSZ peridotite, which is identical to the features of the trace elements of clinopyroxene obtained from the LA-ICP-MS in-situ analysis, while lherzolite is similar to abyssal peridotite. Oxygen fugacities recorded by olivine-spinel of harzburgite equilibrium are+0.96 log units below and-0.14 log units above the FMQ buffer, overlapping the range from MOR to SSZ harzburgite, or from back arc basin peridotite to island arc peridotite. The plot of Ga-Ti-Fe3+# of spinels indicates that the origin of dunite was related to the interaction between peridotite and island arc tholeiite, and the harzburgite was probably the residue after the interaction between peridotite and MOR melt and the interaction between peridotite and hydrous melt at the SSZ environment. The values of∑REE of harzburgite and dunite are lower than those of C1 chondrite, and display the enriched LREE and the U-type REE pattern,which implies the fluid/melt-rock reaction. Taking into account the above data, the authors hold that the Darbute ophiolite was probably formed in the back arc spreading ridge and influenced by subducted fluid/melt.