摘要
攀枝花层状辉长岩侵入体,自下而上可分为四个岩带。各种样品的δ18O值: 8个全岩样品中的6个为+6.27—+6.91‰;23个钛磁铁矿中的19个为+1.28—+2.39‰;21个斜长石中的12个为+6.18—+7.60‰。氧同位素特征表明,岩体源自上地幔。Ⅰ岩带氧同位素平衡温度较低455℃—730℃,可能是成岩后叠加地质作用影响的结果;Ⅱ岩带856—1045℃;Ⅲ岩带652—740℃;Ⅳ岩带62 1.—871℃。
The exposed area of the Panzhihua basic intrusion is about 38 km^2, 19km long and 2km wide. The layered structure in the intrusion is well developed. The intrusion body has K-Ar and U-Pb age of 306—320Ma and it can be divided into 4 zones from bottom to top. The main rocks of zone Ⅰ are fine-grained olivinegabbro, titanomagnetite rock and coarse-grained pegmatitic gabbro; those of zone Ⅱ include titanomagnetite-gabbro and gabbro; the main rock of zone Ⅲ are gabbro and anorthosite and zone Ⅳ is composed of amphibole gabbro.Samples that were studied by oxygen isotope analysis are from zones Ⅰ-Ⅳ. The whole rock δ^(18)O values for 6 samples are+6.27—+6.91％, and for the other 2 samples——+8.99-+9.19％; for 20 of 23 titanomagnetite samples δ^(18)O values range from +0.55 to +3.46％, and for the other 3 samples——from+4.11 to+4.86％ for 12 of 21 plagioclase samples from +6.18 to+7.60％, and for the other 9 samples——+8.12 to +11.99％. One ilmenite sample has-aδ^(18)O value of +4.56％. According to the oxygen isotope determination results it is suggested that the primary magma of the Panzhihua intrusion probably originated from the upper mantle.The △δ^(18)O values of the oxygen isotope fractionation between coexisting plagioclase and titanomagnetite for zone Ⅰ are 5.03-9.46 and the oxygen isotope equilibrium temperature ranges from 455° to 730℃. For zones Ⅱ, Ⅲ, and Ⅳ the △δ^(18)O values of oxygen isotope fraetionation are 2.87-3.94, 4.93-5.85, and 3.87—6.19, respectively. While their oxygen isotope equilibrium temperatures are 871°—1045℃, 650°—740℃ and 621°—871℃, respectively.
出处
《岩石矿物学杂志》
CAS
CSCD
1991年第1期29-36,共8页
Acta Petrologica et Mineralogica
关键词
辉长岩
层状
基性侵入体
氧
同位素
oxygen isotope, oxygen isotope equilibrium temperature, layered basic intrusion, gabbro, Panzhihua
