摘要
近年在新疆北准噶尔构造带的乔夏哈拉-老山口地区发现有苦橄岩存在.苦橄岩与苦橄质玄武岩、玄武玢岩、辉绿岩、安粗岩、粗面岩以及凝灰岩、碳酸盐岩组成洋底苦橄岩建造,总厚大于1780 m,为新的岩层,建议采用'乔夏哈拉组'组名.苦橄岩有橄榄石苦橄岩、橄榄石-辉石苦橄岩和辉石苦橄岩3种.苦橄岩ω(SiO2)39.9%~46.78%;ω(MgO)16.4%~36.67%;ω(Na2O+K2O)0.17%~1.47%,多数小于0.5%;ω(TiO2)0.28%~0.62%,个别1.05%.总体具低硅、低铝、低钛、低碱、高镁特征.稀土元素总量<45×10-6,轻稀土略富集,Eu低正异常.微量元素Li、Be、U、Rb、Sr、Ba、V、F、Bi、Pb等元素明显富集,而Ni、Cr、Co和S明显亏损.表明经过一定程度的分异作用,并有上地壳成分的污染,铂族元素含量接近世界其它地区苦橄岩,具有Pt/Pd<1和贫Os、Ir的特征.
Picrite was discovered in the Qiaoxiahala-Laoshankou region in the north Junggar tectonic zone, Xinjiang, China in recent years. Picrite, picritic basalt, basalt-porphyrite, diabase, latite, trachyte, tuff and carbonate rocks comprise the ocean-floor picrite construct which is more than 1780m thick. It appears to be a new formation and the name “Qiaoxiahala Formation” is proposed. Picrite includes three types: olivine picrite, olivine-pyroxene picrite and pyroxene picrite. As a whole, picrite is low in silicon, ahiminium, titanium, alkali, but high in magnesium, with the following contents: w (SiO2) 39.9-46.78%; w (MgO) 16.4-36.67%; w (Na2O+K2O) 0.17-1.47%, the majority less than 0.5%; w (TiO2) 0.28~0.62%, some up to 1.05%. The gross total of rare earth elements (REE) is less than 45 ×10^-6, light REE is enriched slightly, and the europium content is a low positive anomaly. Microelements, like Li, Be, U, Rb, Sr, Ba, V, F, Bi and Pb, are obviously enriched, while Ni, Cr, Co and S are in the extreme depletion. This suggests that they have been differentiated to a certain degree and contaminated by upper crustal compositions. The platinum group elements (PGE) content is similar to those of other picrites in the world, with the character of Pt/Pd〈1 and low contents of Os and Ir.
出处
《新疆地质》
CAS
CSCD
2005年第4期319-325,共7页
Xinjiang Geology
基金
资助:新疆305项目(2003BA612A-06)
国家科技攻关计划课题(2003BA612A-01)
中国地质调查局国土资源大调查项目(200420190004)项目共同资助