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新疆南天山东段库兹山基性超基性岩带,前人缺乏研究,但该带的岩石成因和形成地质背景对认识南天山的构造格架具有重要意义。该带中的主要岩石类型有单辉橄榄岩,辉绿岩和辉长岩等。单辉橄榄岩的橄榄石为富镁型:Fo为93～96;副矿物铬尖晶石属于高铬低镁型,Cr#(Cr/(Cr+Al)×100)值78～99,Mg#(Mg/(Mg+Fe)×100)值1.8～41.4,属于造山带中的阿拉斯加型超基性岩类型。辉绿岩中辉石为普通辉石,Mg#(Mg/(Mg+Fe)×100)显示一个连续的从高到低的演化趋势,反映了岩浆的分异作用;长石为拉长石和中长石。辉长岩中辉石为普通辉石;斜长石已经蚀变成钠长石,Ab在95以上。辉绿岩和辉长岩K2O含量均很高,平均值分别为0.75和0.85,且LILE相对HFSE明显富集,认为它们可能与单辉橄榄岩同属造山带中的侵入体,形成在南天山的造山阶段。基性岩的同位素年代学指示该岩浆事件由石炭纪延续到二叠纪(331～286 Ma)。
The Kuzishan basic ultramafic rock belt in eastern Tianshan Mountain of Xinjiang Province was scarcely studied. However, the rock genesis and geological background of this belt are of great significance for understanding the Tectonic framework of the southern Tianshan Mountains. The main types of rocks in this zone are harzburgites, diabase and gabbro. The olivine of the harzburgite is a magnesium-rich type with a Fo of 93-96; the sub-mineral chromium spinel belongs to the category of high-chromium and low-magnesium, with Cr # (Cr / (Cr + Al) The value of # (Mg / (Mg + Fe) × 100) is 1.8 ~ 41.4, belonging to the Alaskan-type ultrabasic rocks in the orogenic belt. The pyroxene in the diabase is an ordinary pyroxene, and the Mg # (Mg / (Mg + Fe) x 100) shows a continuous descending trend, reflecting the differentiation of magma; Middle feldspar. Gabbro is a pyroxene pyroxene; plagioclase has been altered into albite, Ab above 95. The diabase and gabbro K2O content are very high, with an average of 0.75 and 0.85, respectively, and LILE is significantly enriched relative to HFSE, suggesting that they may be intrusions in the orogenic belt of khihenite, forming in the southern Tianshan Orogenic phase. Isotopic chronology of basic rocks indicates that the magmatic event extended from the Carboniferous to the Permian (331-286 Ma).