P-T-t-deformation paths recorded by kinzigites during diapirism in the western Variscan belt (Golfe du Morbihan, southern Brittany, France)     

C. AUDREN  C. TRIBOULET 《Journal of Metamorphic Geology》1993,11(3):337-356

Abstract The high-grade metamorphic rocks of southern Brittany underwent a complex tectonic evolution under various P-T conditions (high-P, high-T), related to stacking of nappes during Palaeozoic continentcontinent collision. The east to west thrusting observed in the whole belt is strongly perturbed by vertical movements attributed to the ascent of anatectic granites in the high-T area. The field reconstruction of subvertical, closed elliptical structures in gneisses and migmatites, associated with the subhorizontal, doubly radial pattern of stretching lineation in the mica schists, suggests the existence of an elliptical diapiric body buried at depth beneath the present erosion level. Deformation is associated with a complex P-T evolution partly recorded in aluminous gneisses (kinzigites, e.g. morbihanites). A chronology of successive episodes of mineral growth at different compositions is established by detailed studies of the mineral-microstructure relationships in X-Z sections, using the deformation-partitioning concept (low- and high-strain zones). Several thermometric and barometric calibrations are applied to mineral pairs either in contact or not in contact but in equivalent microstructiiral positions with respect to the deformation history. This methodology provides a continuous microstructural control of P-T variations through time and leads to three P-T-t-d paths constructed from numerous successive P-T estimations. Path 1 is a clockwise retrograde path preserved in low-strain zones, which records general exhumation movements after crustal thickening. Paths 2 and 3 are clockwise prograde/retrograde paths from high-strain zones; they are interpreted and discussed in the light of models of crustal anatexis and upward movement of magma (diapirism). Deformation and P-T effects induced by diapirism can be distinguished from the general deformation-metamorphic history of a belt, and would seem to be produced during a late stage of its history. The present microstructural-petrological approach to defining successive mineral equilibria in relation to progressive deformation steps provides a far more accurate evaluation of the metamorphic evolution than is possible by ‘standard’thermobarometry.  相似文献   

鄂尔多斯盆地上古生界高分辨率层序地层分析   总被引：35，自引：1，他引：35  

郑荣才  文华国  梁西文 《矿物岩石》2002,22(4):66-74

按基准面旋回原理，将鄂尔多斯盆地上古生界本溪组（C2b)、太原组（P1t）、山西组(P1s)和下石盒子组（P1xs)划分为3个超长期、8个长期、19个中期和62个短期旋回层序：较为详细地介绍了各级别层序的结构类型、叠加样式和沉积演化序列；建立以长期旋回层序为年代地层框架，中期旋回层序为等时地层对比单元的层序的地层格架；并讨论高分辨率层序地层与天然气藏的关系。  相似文献   

Study of the Earth’s free core nutation by tidal gravity data recorded with international superconducting gravimeters   总被引：2，自引：0，他引：2  

Jianqiao Xu  Heping Sun  Shaocong Luo 《中国科学D辑(英文版)》2002,45(4):337-347

By stacking high-precision tidal gravity observations obtained with superconducting gravimeters at six stations in China, Japan, Belgium, France, Germany and Finland, the local systematical discrepancies in the parameter fitting, caused by atmospheric, oceanic tidal loading and the other local environmental perturbations, are eliminated effectively. As a result, the resonance parameters of the Earth’s free core nutation are accurately determined. In this study, the eigenperiod of free core nutation is given as 429.0 sidereal days, which is in agreement with those published in the previous studies. It is about 30 sidereal days less than those calculated in theoretical models (about 460 sidereal days), which confirms the real ellipticity of the fluid core of the Earth to be about 5% larger than the one expected in assumption of hydrostatic equilibrium. The quality factor (Q value) of free core nutation is given as about 9543, which, compared with those determined before based on the body tide observations, is much larger, but more close to those obtained using the VLBI observations. The complex resonance strength is also determined as (−6.10×10⁻⁴, −0.01 ×10⁻⁴)°/h, which can principally describe the deformation characteristics of an anelastic mantle.  相似文献   

不对称抽道集共反射面元叠加方法探讨     

邱苏胡旭芝  沈骥千 《中国煤田地质》2003,15(2):49-51,F004,58

总结不对称抽道集共反射面元叠加方法的工作经验，提出自由观测面自由反射界面不对称抽道集共反射面元叠加方法的处理思路和计算方法。在自由观测面的条件下，反射界面可分为简单倾斜平面、规则曲面和自由反射界面三种情况，针对不同情况讨论共反射面元的叠加方法。综合一般情况下的共反射面元叠加方法，提出了“鳞片法”的处理思路。  相似文献   

基于共反射点叠加的观测参数选择   总被引：1，自引：2，他引：1  

朱海波  黄德济  贺振华 《物探化探计算技术》2004,26(2):121-124

在地震勘探数据处理中，通常采用的共中心点(CMP)叠加技术对于复杂的地质构造难以取得好的效果。若通过从道间距、覆盖次数等观测参数与目标层地层倾角、共反射点离散度的关系出发，并结合模型正演，对复杂构造地层的观测参数选取进行优化，使之能对目标层尤其是逆断层下降盘的阴影层段进行较充分的“照明”，即可得到共反射点叠加剖面，这对共反射点叠加是一项有益的研究。  相似文献   

Rapid estimation of relative and absolute delay times across a network by adaptive stacking   总被引：6，自引：0，他引：6  

N. Rawlinson  B. L. N. Kennett 《Geophysical Journal International》2004,157(1):332-340

  相似文献   

ECONOMIC GEOLOGY     

《Abstract of Chinese Geological Literature》2014,(2)

正20140805Fan Baocheng(Xi’an Center of Geological Survey,China Geology Survey,Xi’an710054,China);Meng Guanglu The Geological Evolution and Metallization of TalasKalatawu Block in Northern Tianshan,Kyrgyzstan(Northwestern Geology,ISSN1009-6248,CN61-1149/P,46(2),2013,p.54-  相似文献   

Lateral variation in Moho depth around the southern Tanlu fault zone and its adjacent area          下载免费PDF全文

Dequan Hong  Xianliang Huang  Yun Yang  Ziwen Bao  Xiaoli Wang  Xueying Wang 《地震科学（英文版）》2021,34(1):77-87

We estimated Moho depth beneath the southern Tanlu fault zone and its adjacent area using common-conversion-point(CCP)stacking of receiver fun-ctions,which were computed from teleseismic records of the CEArray.Our estimated Moho depth matches well with 2-D profiles derived from active-source deep seismic reflection surveys,suggesting that the calculated the Moho depth map is likely accurate beyond the 2-D profiles.Overall,the estimated Moho depth map showed a high spatial correlation with tectonic provinces,i.e.,Moho topographic boundaries are in good agreement with geological boundaries.Beneath the Dabie orogenic belt and the mountainous areas in southern Anhui Province,the Moho lies relatively deep,and there is an obvious difference in Moho depth between the two sides of this segment of the Tanlu fault.We further selected four depth profiles with dense instrumentation to show Moho depth changes across different tectonic blocks in the study area.We saw two step-like changes in Moho depth beneath the Xiangfan-Guangji and Gushi-Feizhong,which run parallel along the WNW-ESE direction and delineate the southern and northern bounds of the northern Dabie orogenic belt,which is likely the suture zone between the North China Block and South China Block.Crust beneath the northeast corner of the study area is significantly thinner than other areas,which is consistent with the crustal detachment model proposed for suturing between the North and South China blocks in the region east to the Tanlu fault.  相似文献   

塔里木盆地北部古生界密集段分布型式与海平面变化的关系   总被引：4，自引：1，他引：4  

樊太亮 《地球学报》1998,19(3):308-314

塔里木盆地北部震旦纪－古生代层序地层格架中,发育着６个可作为生油层的大型密集段或复合密集段。密集段在层序格架中有４种叠置型式,即进积组合,退积组合,加积组合和上超组合。不同的叠置型对应于不同的海平面变化过程。相应地,密集段的发育规模及时空展布有着明显的差别,其中,在退积层序组合和进积层序组合中,密集段垂向上相互叠置,侧向上彼此邻接,构成层数与厚度复杂多变的复合密集段,是盆地中的主力生油层。  相似文献   

The Quaternary Lancaster Sound trough‐mouth fan,NW Baffin Bay     

Gang Li  David J.W. Piper  D. Calvin Campbell 《第四纪科学杂志》2011,26(5):511-522

The development of the Lancaster Sound Trough Mouth Fan (TMF) and glacial history in Arctic Canada were studied using a high‐resolution seismic profile across the entire fan and two piston cores. Stacked tills separated by erosion surfaces on the shelf pass seaward through till deltas into thick transparent glacigenic debris flow (GDF) deposits on the slope, separated by thin, well‐stratified glaciomarine layers. An age model was built by ties to the Ocean Drilling Program Site 645. The deepest GDF on the seismic profile was indicative of the onset of shelf‐crossing glaciation in the Early Pleistocene. The transition of the growth of Lancaster Sound TMF from an aggradational sequence (unit M) to an aggradational–progradational sequence (unit F) occurred at the Middle Pleistocene transition in glacial cyclicity. In the most recent glacial cycle, GDF sheets were deposited during Heinrich events 4 and 2 according to the correlation of the main detrital carbonate beds in two piston cores. The outmost till wedge reflects the maximum advance of the grounding glacier, far seaward of previously proposed Last Glacial Maximum ice extent. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献