In this paper, using the 1999 ~ 2007 GPS velocity field data, and by choosing the optimal block model, we obtained the deformation models applicable to the boundary zones of major blocks and the slip rates of block boundary faults on the mid-southern segment of the North-South Seismic Belt. The results show that: on the Longmenshan fault zone, the tensional and compressive slip rate is small on the Baoxing-Wenchuan segment, about 0. 5 ~ 1.8mm·a^-1, and the rate is relatively significant on the segment of the Wenchuan--Maoxian, as 1.8 ~3.8mm·a^-1; on the Xianshuihe fault belt, there is a certain difference in spatial distribution between the tensional slip rag.e and strike-slip rate: the tensional slip rate ( 8. lmm~a-1) is bigger than the sinistral strike-slip rate ( 4.8mm·a^-1) at the north of the Luhuo region; the tension and compression slip rate is basically the same as the strike-slip rate at Luhuo-Dawu; the Dawu-Kangding section presents a trend of decreased strike-slip rate and increased tensional slip rate; the Kangding-ghimian segment shows a strike-slip nature; the strike-slip rate is significantly greater than the tension/compression rate on the Xiaojiang fault zone; the slip rate on the Red River fault zone shows obvious spatial segmentation, the slip rate is smaller in its northwest part, but with a certain amount of tensional/compression component, 4. 7mm·a^-1 on the Jingdong segment. The segment east of Jingdong ( western Gejiu) is mainly of strike-slip, with a slip rate of 4. 5mm·a^-1. 相似文献
INTRODUCTIONGeological investigations since the1970s have shown that the sub_longitudinal Jinshajiang andHonghe(Red River)fault zones constitutethe western boundary of“Rhombic Sichuan_Yunnan Block”onthe Sichuan_Tibet border and display mainly dextral sh… 相似文献
The Helong block, located in southeastern Jilin Province, was thought to be an Archean geological unit in the most northeast part of the North China Craton (NCC)[1,2]. Previous geological survey sug-gested that this block is mainly composed of two parts: Jinchengdong Archean metamorphic supracrustal rocks intruded by Archean TTG complex[3―5], and the Bailiping granite[6,7] distributed in the Shiliping-Bai- liping-Guangping area. Both of them were thought as the Jinchengdong (or Helong… 相似文献
The Betic Cordillera and the Moroccan Rif together form one of the smallest and tightest orogenic arcs on Earth and almost completely close the Mediterranean to the west. For the explanation of the geodynamic evolution of the mountain belt, palaeomagnetic data that generally found clockwise block rotations in the Iberian and anticlockwise rotations in the Moroccan part of the mountain belt, have played a key role in recent works. This palaeomagnetic study has found new constraints on the rotations and timing of the peridotitic bodies outcropping in the key position at the westernmost margin of the mountain belt, in Ceuta and Beni Bousera (Rif, northern Africa).Detailed thermal demagnetization of 115 individually oriented samples from 14 sites was combined with rock magnetic and scanning electron microscopic experiments to analyze the magnetic mineralogy responsible for the remanences and the mechanisms and relative times of their acquisition. In Ceuta, up to three magnetic components, and in Beni Bousera, up to two magnetic components have been found, that are all to be interpreted as chemical remanent magnetizations (CRM). The data suggests the following succession of geodynamic events affecting the peridotites until recent times: (1) after their exhumation and subsequent cooling about 20 Ma ago, they recorded a characteristic remanent magnetization of both normal and reversed polarities, carried by (pseudo-)single-domain magnetite grains; (2) after their dismembering, the Ceuta peridotites were tilted southward by 22–34° about a horizontal or tilted axis (up to plunge 50°) with an azimuth of 72–145° and the Beni Bousera peridotites were rotated anticlockwise by 72.3 ± 12.1° about a vertical axis and (3) both recorded another magnetic signal of normal polarity only, carried by multi-domain magnetite grains; and finally (4) the Ceuta peridotites rotated anticlockwise by 19.7 ± 5.9° about a vertical axis.This study provides the first palaeomagnetic data for the Ceuta peridotites that, with their tilt and recent small net rotation, had a distinct geodynamic evolution from the large net rotations about vertical axes in Beni Bousera and Ronda (Betic Cordillera). Moreover, earlier palaemagnetic data for Beni Bousera is improved, as mixed polarities have been found in the older of the remanences for the first time, and its interpretation as a CRM changes the rotation timing that was proposed previously. The sequence of events exposed in this work are important constraints that need to be incorporated in any geodynamic model of the evolution of the Betic–Rifean mountain belt. 相似文献