By analyzing the balanced cross sections and subsidence history of the Longmen Mountain thrust belt, China, we concluded that it had experienced five tectonic stages： （1） the formation stage （T3x） of the miniatur...By analyzing the balanced cross sections and subsidence history of the Longmen Mountain thrust belt, China, we concluded that it had experienced five tectonic stages： （1） the formation stage （T3x） of the miniature of Longmen Mountain, early Indosinian movement, and Anxian tectonic movement created the Longmen Mountain; （2） the stable tectonic stage （J1） where weaker tectonic movement resulted in the Longmen Mountain thrust belt being slightly uplifted and slightly subsiding the foreland basin; （3） the intense tectonic stage （J2-3）, namely the early Yanshan movement; （4） continuous tectonic movement （K-E）, namely the late Yanshan movement and early Himalayan movement; and （5） the formation of Longmen Mountain （N-Q）, namely the late Himalayan movement. During those tectonic deformation stages, the Anxian movement and Himalayan movement played important roles in the Longmen Mountain＇s formation. The Himalayan movement affected Longmen Mountain the most; the strata thrust intensively and were eroded severely. There are some klippes in the middle part of the Longmen Mountain thrust belt because a few nappes were pushed southeastward in later tectonic deformation.展开更多
To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were mea...To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400—2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kbler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KID2q° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KID2q° ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KID2q° ranging from 0.38 to 0.40. According to a KID2q° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kbler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217—2213 nm, the lower member of the Hekou Formation at 2214—2206 nm, and the upper member of the Hekou Formation at 2205—2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors.展开更多
基金support from the National Natural Science Foundation of China (grant No.40672143,40472107,and 40172076)the National Major Fundamental Research and Development Project (grant No.2005CB422107 and G1999043305)+1 种基金the Development Foundation of Key Laboratory for Hydrocarbon Accumulation of Education Ministry (grant No.2003-03)the Project of Southwestern Exploration and Development Division Company,SINOPEC (GJ-51-0602).
文摘By analyzing the balanced cross sections and subsidence history of the Longmen Mountain thrust belt, China, we concluded that it had experienced five tectonic stages： （1） the formation stage （T3x） of the miniature of Longmen Mountain, early Indosinian movement, and Anxian tectonic movement created the Longmen Mountain; （2） the stable tectonic stage （J1） where weaker tectonic movement resulted in the Longmen Mountain thrust belt being slightly uplifted and slightly subsiding the foreland basin; （3） the intense tectonic stage （J2-3）, namely the early Yanshan movement; （4） continuous tectonic movement （K-E）, namely the late Yanshan movement and early Himalayan movement; and （5） the formation of Longmen Mountain （N-Q）, namely the late Himalayan movement. During those tectonic deformation stages, the Anxian movement and Himalayan movement played important roles in the Longmen Mountain＇s formation. The Himalayan movement affected Longmen Mountain the most; the strata thrust intensively and were eroded severely. There are some klippes in the middle part of the Longmen Mountain thrust belt because a few nappes were pushed southeastward in later tectonic deformation.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 40072092) the Dust Storm Project (Grant No. KZCX20305-ADEC).
文摘To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400—2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kbler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KID2q° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KID2q° ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KID2q° ranging from 0.38 to 0.40. According to a KID2q° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kbler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217—2213 nm, the lower member of the Hekou Formation at 2214—2206 nm, and the upper member of the Hekou Formation at 2205—2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors.
