摘要
Using XRD measurements of illite crystallinity,b0values of K-rich white micas and chemical compositions of chlorites combined with homogenization temperatures of fluid inclusions in calcite,the metamorphic P–T conditions of very low-grade metapelites from different depths in the 7 km Hongcan Well 1 in the Zoige?Depression,Sichuan,China,have been obtained in this paper.Knowledge of the tectonic evolution of the studied basin allows us to derive geothermal curves for Middle and Late Triassic time(the geothermal peak)and the present day(from thermal logging of the borehole).The retrograde P–T tracks from clockwise P–T–t loops have been revealed by the plotting of individual samples on each geotherm,which can be interpreted by the lithospheric thickening due to sedimentation and folding followed by continuous uplift and erosion.A stratigraphic log indicates that the Well penetrates the steep limb of a fold which perturbed the peak geotherm and caused some P–T paths to cross.
Using XRD measurements of illite crystal- linity, bo values of K-rich white micas and chemical compositions of chlorites combined with homogenization temperatures of fluid inclusions in calcite, the meta- morphic P-T conditions of very low-grade metapelites from different depths in the 7 km Hongcan Well 1 in the Zoig~ Depression, Sichuan, China, have been obtained in this paper. Knowledge of the tectonic evolution of the studied basin allows us to derive geothermal curves for Middle and Late Triassic time (the geothermal peak) and the present day (from thermal logging of the borehole). The retrograde P-T tracks from clockwise P-T-t loops have been revealed by the plotting of individual samples on each geotherm, which can be interpreted by the lithospheric thickening due to sedimentation and folding followed by continuous uplift and erosion. A strati- graphic log indicates that the Well penetrates the steep limb of a fold which perturbed the peak geotherm and caused some P-T paths to cross.
基金
supported by the National Natural Science Foundation of China(41302047)
the Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(CHD2011JC185)
关键词
变质泥质岩
晚三叠世
若尔盖
构造意义
X射线衍射测量
路径
坳陷
伊利石结晶度
P-T path · Very low-grade metapelitesbo values of K-rich white mica ·Kfibler index ·Chlorite geothermometer ·Hongcan Well 1 ~Zoig~ Depression