论文部分内容阅读
在柴北缘蛇纹石化纯橄岩脉中发现一粒原位生长的巨晶锆石,呈紫红色,大小约2mm×(3～4)mm.根据BSE图像观察,在橄榄石与蛇纹石粒间有微粒锆石(30～50μm),局部已聚集成较大颗粒(100～300μm),由此推测巨晶锆石是从热液流体中结晶的.局部还可见到斜锆石(白色)在锆石(灰色)中呈孤岛状,表明前者形成早,后者形成晚.微粒斜锆石(50～100μm)是由斜锆石相(白色,3～5μm)和橄榄石相(黑色,<5μm)组成的多相集合体,这些现象表明锆石是由斜锆石与含硅流体反应形成的.因此,锆石的形成与蛇纹石化过程有成因联系.SHRIMP法锆石U-Pb定年得到两组谐和年龄,分别为(414±13)和(371±9)Ma.这可能反映锆石有两个主要生长期,对应有两期流体活动.
In the northern margin of the Qaidam Basin, an in situ growth giant gigantic zircon was found in the serpentiniferous dugout vein of the northern margin of the Qaidam Basin, with a fuchsia color and a size of about 2 mm × 3 to 4 mm. According to BSE images, It is speculated that giant zircons crystallize from the hydrothermal fluid, and there are also some clinoptilolite (white ) Shows an island shape in zircon (gray), indicating that the former forms early and the latter forms late. Microporphyrodite (50-100 μm) is composed of an orthoclase zircon (white, 3-5 μm) and an olivine phase , <5μm). These phenomena indicate that zircon is formed by the reaction of orthorhombic zirconia with silicon-bearing fluid, and therefore, the formation of zircon has a causal relationship with the serpentinization process. The SHRIMP zircon U- Pb dating gives two sets of harmonic ages, which are (414 ± 13) and (371 ± 9) Ma, respectively, which may reflect that zircon has two main growth periods, corresponding to two phases of fluid activity.