新疆柯坪二叠纪层状玄武岩的发育特征及其地质意义

DISTRIBUTION CHARACTERS OF PERMIAN BASALTS AND THEIR GEOLOGICAL SIGNIFICANCE IN THE KALPIN AREA,XINJIANG

通过野外实地测量和遥感影像识别,并对不同剖面的发育状况进行了对比。新疆柯坪地区发育的二叠纪玄武岩共可分为8层,包括库普库兹曼组2层和开派兹雷克组6层。多层玄武岩是多期喷发作用的结果,每次喷发可以来自不同的岩浆房或火山通道,但岩浆源区基本一致。每期喷发作用都具有一定的序列,先是稳定的熔岩流,发育柱状节理,往上则为致密块状玄武岩,在喷发末期发育火山角砾岩或凝灰岩。多期玄武岩浆喷发作用,指示了该区二叠纪玄武岩的岩浆房经历了"积聚—喷发—再积聚—再喷发"的过程,而熔融岩浆的源区则经历了不断"部分熔融"和"岩浆抽提"的过程。

This paper systematically describes the multilayered Permian basalts occurring in the Kalpin area of Xingjiang,by in-situ measurements as well as interpretation of satellite images.Three sections of basalt outcrops have been studied.The spatio-temporal distribution patterns of these basalts form a basis for future study of their geochemistry,petrogenesis and geodynamics.The Kalpin basalts can be divided into eight layers,the early two of which occur in the Kupukuziman Formation,and the later six in the Kaipaizileike Formation.The multilayered basalts represent multiple eruptions from the same magma source.They may have come from different magma chambers or different volcanic vents,and they may have erupted quickly with crystallized plagioclase phenocrysts.Each eruption started with steady lava flow usually with columnar jointing,followed by successive flood flow consolidated to block basalt,and terminated by volcanic breccia or tuff.The multiple eruptions of basaltic magma indicate multiple cycles of ＂magma accumulation and eruption＂ in the magma chamber,and the process of ＂partial melting＂ and ＂magma extraction＂ from the source area.