Based on an extensive borehole survey of the Middle Jurassic coat-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin （NQB）, a total of 20 rock types and 5 sedimentary facies were identified, includ...Based on an extensive borehole survey of the Middle Jurassic coat-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin （NQB）, a total of 20 rock types and 5 sedimentary facies were identified, including braided river, meandering river, braided delta, meandering river delta, and lacustrine facies. The distribution of rock types and sedimentary facies contributed to the reconstruction of three periods＇ sedimentary facies maps of the Middle Jurassic in the Saishiteng coalfield, namely, the Dameigou age, the early Shimengou age and the late Shimengou age. That also provided the basis for the development of a three-stage depositional model of the Middle Jurassic in the NQB, indicating the lacustrine basin of the NQB in the Dameigou age and early Shimengou age were corresponding to an overfill basin, and that in the late Shimengou age was related to a balanced-fill basin. The analysis of the stability and structure of coat seams based on sedimentary facies maps showed that the preferred coal-forming facies in the Saishiteng coalfield were inter-delta bay and interdistributary bay of lower delta plain in the Dameigou age. In particular, the swamps that developed on the subaqueous pataeohigh favored the development of thick coat seams. Thus, ruinable coal seams may also be found along the Pingtai pataeohigh in the western part of the Saishiteng coalfield.展开更多
CHONDRULES are the major constituent of chondrites, but the nature of their origin remains elusive. Models based on nebular settings have attracted much support since Wood suggested that they formed there ascondensate...CHONDRULES are the major constituent of chondrites, but the nature of their origin remains elusive. Models based on nebular settings have attracted much support since Wood suggested that they formed there ascondensates. Subsequently, the melting of dust in the nebula has been widely invoked. Recently,however, models suggesting that chondrules formed in parent body regoliths have been revived, couldhelp to explain the coexistence of chondrules with chemically differentiated clasts The Boxian meteorite is a fall and was originally described as L4. The widely quoted classification of the chondrite is LL4. In this study, 362 chondrules were separated from the Boxian meteorite,and were measured for their grain sizes, masses and morphologies. 101 of these chondrules were successfully split and parts of them made into polished blocks; the remaining segments were individually set asidefor future oxygen isotopic analyses. Mineralogical investigation of the 101 chondrules was performed展开更多
基金supported by the National Natural Science Foundation of China(41030213, 41502108)the Major National Science and Technology Program of China(2011ZX05033-002)
文摘Based on an extensive borehole survey of the Middle Jurassic coat-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin （NQB）, a total of 20 rock types and 5 sedimentary facies were identified, including braided river, meandering river, braided delta, meandering river delta, and lacustrine facies. The distribution of rock types and sedimentary facies contributed to the reconstruction of three periods＇ sedimentary facies maps of the Middle Jurassic in the Saishiteng coalfield, namely, the Dameigou age, the early Shimengou age and the late Shimengou age. That also provided the basis for the development of a three-stage depositional model of the Middle Jurassic in the NQB, indicating the lacustrine basin of the NQB in the Dameigou age and early Shimengou age were corresponding to an overfill basin, and that in the late Shimengou age was related to a balanced-fill basin. The analysis of the stability and structure of coat seams based on sedimentary facies maps showed that the preferred coal-forming facies in the Saishiteng coalfield were inter-delta bay and interdistributary bay of lower delta plain in the Dameigou age. In particular, the swamps that developed on the subaqueous pataeohigh favored the development of thick coat seams. Thus, ruinable coal seams may also be found along the Pingtai pataeohigh in the western part of the Saishiteng coalfield.
文摘CHONDRULES are the major constituent of chondrites, but the nature of their origin remains elusive. Models based on nebular settings have attracted much support since Wood suggested that they formed there ascondensates. Subsequently, the melting of dust in the nebula has been widely invoked. Recently,however, models suggesting that chondrules formed in parent body regoliths have been revived, couldhelp to explain the coexistence of chondrules with chemically differentiated clasts The Boxian meteorite is a fall and was originally described as L4. The widely quoted classification of the chondrite is LL4. In this study, 362 chondrules were separated from the Boxian meteorite,and were measured for their grain sizes, masses and morphologies. 101 of these chondrules were successfully split and parts of them made into polished blocks; the remaining segments were individually set asidefor future oxygen isotopic analyses. Mineralogical investigation of the 101 chondrules was performed
