排序方式： 共有43条查询结果，搜索用时 328 毫秒
11.
E. Be Mezeme M. Faure Y. Chen A. Cocherie J-Y. Talbot 《International Journal of Earth Sciences》2007,96(2):215-228
In the southern French Massif Central, the Rocles leucogranite of Variscan age consists of three petrographic facies; textural
analysis shows that they experienced the same subsolidus deformation. New chemical U-Th-Pb dating on monazite yielded 324 ± 4 Ma
and 325 ± 5 Ma ages for muscovite-rich and biotite-rich facies respectively. AMS-study results agree with petrostructural
observations. The magnetic planar and linear fabrics, which correspond to the preferred orientation of biotite and muscovite,
are consistent with the foliation and lineation defined by the preferred mineral orientation. This fabric developed during
pluton emplacement. The accordance of this granite foliation with that observed in the host rock, suggests that the Rocles
pluton is a laccolith, but its present geometry resulted from post-emplacement southward tilting due to the uplift of the
Late Carboniferous Velay dome. Restoration of the primary geometry of the pluton and its country-rocks to a flat-lying attitude
places the granite lineation close to the trend measured in other plutons of the area. This restoration further supports the
interpretation of the Rocles laccolith as a pluton emplaced along a tectonic contact reactivated during the late-orogenic
collapse of the Variscan Belt. 相似文献
12.
Anisotropy of magnetic susceptibility and structural geology of the ca. 1.45 Ga Karlshamn pluton (southern Sweden) are used
to study its emplacement and structural evolution. The Karlshamn pluton is one of the largest metaluminous A-type granitoid
intrusions in southern Sweden. It is a multiphase body made up of two suites that differ in composition but which have similar
crystallization ages. The magmatic foliation, ductile shear zones and granite–pegmatite filled fractures were mapped as well
as the metamorphic foliation and extension lineation in the metamorphic host rocks. The anisotropy of magnetic susceptibility
was used to map the magnetite petrofabric of the pluton, providing a larger data set for both the magmatic foliations and
lineations, which could not be mapped in the field. The fabrics within the pluton are continuous with the metamorphic fabrics
in the country rocks. Both the pluton and the country rock fabrics were folded during ENE–WSW compression, while the pluton
was still a magma mush. The stress field orientation during cooling of the pluton is determined on the basis of magmatic,
ductile and brittle structures in the Karlshamn pluton that formed successively as the pluton cooled. The compressional event
is referred to as the Danopolonian orogeny and therefore the Karlshamn granitoids, and other plutons of similar composition
and age in central and southern Sweden, on the Danish Island of Bornholm, and in Lithuania, may be considered as syntectonic
intrusions and not as anorogenic, as was previously thought. 相似文献
13.
14.
The Cretaceous Kusandong Tuff, Korea, is a thin (1–5 m thick) but laterally extensive (~ 200 km) silicic ignimbrite emplaced in a fluviolacustrine basin adjacent to a continental volcanic arc. The tuff has been used as an excellent key bed because of its great lateral continuity and unique lithology, characterized by the virtual absence of juvenile clasts and an abundance of quartz and feldspar crystals (up to 55–73 vol.%). The tuff is mostly massive and ungraded and locally shows crude internal layering, basal inverse grading and near-top normal grading of crystals, either erosional or non-erosional lower surfaces, and flat-lying to imbricated grain fabrics. Fragile intraformational clasts of mudstone and tuff are also included. These features provide only ambiguous information on the properties of the responsible pyroclastic density currents: i.e. whether they were dense and laminar or dilute and turbulent. The overall lateral continuity and sheet-like geometry of the tuff suggests, however, that the transport system of the currents was highly expanded, dilute, and turbulent. A plug-flow or slab-flow model cannot explain the origin of crude internal layering, imbricated grain fabrics, and the high crystal content, which is most likely the result of vigorous sorting processes within a dilute and turbulent current. Features indicative of deposition from a dense and laminar transporting medium are locally present, suggesting that a dense and laminar depositional system could develop locally at the base of the dilute and turbulent transport system. The virtual absence of juvenile clasts in the tuff is interpreted to be due to rapid ascent, sudden decompression, and full fragmentation of silicic magma into fine glass shards and crystals. Scarcity of basement-derived accidental components together with the absence of pumiceous fallout deposits beneath the tuff is interpreted to be due to shallow-level fragmentation of magma followed by immediate generation of pyroclastic density currents from shallow-level blasts at the onset of eruption. The eruption occurred through multiple vent sites in a short period of time, producing a seemingly single but actually composite ignimbrite unit. Such an eruption was probably possible because of a regional tectonic event within the basin or in its vicinity. It is proposed that a composite ignimbrite with the characteristics of the Kusandong Tuff can be an exemplary product of syntectonic volcanism that can provide an insight into the interpretation of structural and stratigraphic evolution of a sedimentary basin. 相似文献
15.
在江南造山带的东段皖浙赣交界地区发育一系列花岗岩岩体,区域上,岩体呈条带状,NE—SW向雁行排列,平行于赣东北断裂带分布;微观下,岩浆流动组构残迹、蠕英石的普遍发育及固态塑性变形证明了该地区岩体变形经历了从岩浆—亚岩浆—固态变形的一个持续转变的过程;岩体锆石年龄与邻区岩体的变质变形年龄有很好的耦合性。由此可见研究区变形花岗岩体为同构造花岗岩,是岩浆在侵位冷凝过程中受到赣东北断裂带强烈构造作用影响的产物。LA-ICP-MS锆石U-Pb同位素定年结果表明:灵山岩体形成于783±14 Ma;莲花山岩体形成于780±12 Ma,属于新元古代岩浆活动。扬子板块与华夏板块碰撞导致江南造山带新元古界的岩群普遍遭受区域变质、变形作用,同构造花岗岩的构造变形特征正是区域构造变形的表现,因此该同构造岩体的年龄可能作为扬子板块与华夏板块仍在挤压、碰撞的年代学证据。 相似文献
16.
海参花是雌海参的性腺,在海参加工过程中常被作为下脚料,但它含有丰富的营养成分和多种活性因子,本研究检测了海参花的一般营养物质、元素含量以及氨基酸组成,同时,研究了海参花水提取物和乙醇提取物对人卵巢癌OVCAR 3细胞增殖以及对其雌二醇分泌的影响。结果表明,海参花含水量为86.63%,粗蛋白、粗脂质和粗多糖（干重）占比分别为65.06%、14.82%和1.93%。共检测出17种氨基酸,总氨基酸含量为519.09 mg/kg。其中,必需氨基酸含量为197.04 mg/kg。海参花还含有多种对人体有益的元素。海参花提取物对人卵巢癌OVCAR 3细胞的增殖有明显的抑制作用,海参花水提取物、乙醇提取物均可提高细胞培养液上清液中雌二醇的含量,其中乙醇提取物可显著提高上清液中雌二醇的含量（P<0.01）。以上表明,海参花的营养丰富,其提取物能显著促进人卵巢癌OVCAR 3细胞雌二醇的分泌调节,因此具有很高的开发利用价值。 相似文献
17.
MIKE BENTLEY 《地球表面变化过程与地形》1996,21(6):493-507
The nested moraines of the Chilean Lake District have been used to establish a glacial chronology for southernmost South America. This paper focuses on non-climatic controls which may have modulated the climatic signal. It presents a model for formation of the moraines around Lagos Puyehue and Rupanco where there is a nested complex dating from the last glaciation. These moraines can be divided into two types on the basis of their form, position and constituent materials: rampart moraines are broad amalgamated moraine complexes whilst ridge moraines are narrow single ridges usually located around lakeshores. Both types have lateral moraines with low up-glacier longitudinal gradients. Sections in the moraines show they are largely composed of stratified glaciofluvial sediments overthrust on their proximal flanks by clay-rich diamicts containing reworked glaciofluvial material. Despite their different characteristics, a single model explains the features of both moraine types and their location around the down-glacier ends of the lakes. Moraine formation depends crucially on the presence of a layer of water-saturated, fine, impermeable sediment in the lake basins which allows the glacier lobes to advance with negligible surface gradients, probably on a deforming bed. Although the formation of moraines requires a climatically triggered advance, their precise position is not dictated by climatic factors but by contrasts in sediment permeability and grain-size. 相似文献
18.
This paper shows the evolution of time-constrained two-dimensional scaled analogue models of doubly vergent thrust systems in the presence of syntectonic sedimentation. Two sets of experiments were considered: (1) the addition of a syntectonic layer composed of a polymer and overlying sand in the prowedge; and (2) the addition to the previous condition of a progradational sedimentary load. Results from the first set of experiments indicate that the foreland fold-and-thrust belt has a strong relationship with the competence of the syntectonic layers. When the competence is low, the deformation produces tight asymmetric detachment-folds. As the competence increases, the fold-and-thrust belt shows break-trough folds with longer and better defined foreland-vergence. Results from the second set of experiments indicate that structural vergence is determined by the sense of progradation of the syntectonic layers, and in the case of strong aggradation at the prowedge, extension and reactive diapirism form contemporaneously with the contraction. Three end-members are proposed for mountain front thrust systems formed in the presence of syntectonic polymer and sand sedimentation: (1) outcropping fold-and-thrust belt sequence, in the case of no syntectonic sedimentation; (2) long displacement blind-thrust sheets, in the case of under-filled basins and (3) short displacement blind-thrust sheets, in the case of over-filled basins. All results indicate that ductile units at the base of syntectonic layers increase the displacement of the underlying frontal thrusts at the prowedge, and reduce the critical taper. Results also indicate that at very high sedimentary rates and hyper-critical taper conditions the prowedge collapses. Conclusions drawn from this research may be applied as an analogue to foreland evolution and to evaluate hydrocarbon generation, migration, and entrapment in thrust belts in areas where seismic imaging is generally poor. 相似文献
19.
四合堂剪切带活动时代及其对燕山运动B幕时间的限定 总被引：4，自引：0，他引：4
翁文灏以燕山为标准地区创名的中生代"燕山运动",现今人们将其分为A幕与B幕,各自对应着区域性角度不整合,但发生的准确时间一直无法确定。燕山构造带中段的云蒙山地区,发育了著名的四合堂逆冲型韧性剪切带,是燕山运动B幕的产物。该韧性剪切带出现在早白垩世初云蒙山复式岩体的北部边缘,上盘向南南西运动,周边的变质基底、中—新元古代盖层及晚侏罗世与早白垩世初期岩体一同卷入了变形。剪切带内及周边发育了大量同构造岩脉,可区分出早、中、晚3个阶段,对应着剪切带活动早、中、晚阶段。本次工作中分别从早、中、晚3阶段同构造岩脉中获得了锆石LA-ICP-MSU-Pb年龄,分别为143.0±2.1Ma、140.8±1.4Ma和137.5±2.4Ma。这可靠地指示了四合堂韧性剪切带的活动时间为143～138Ma。这也表明,以逆冲活动为特征的燕山运动B幕(尤其是燕山造山带中段)发生的时间就是143～138Ma。这一结果与近年来该B幕事件角度不整合之上、下地层中所获得火山岩锆石年龄相吻合。 相似文献
20.
Jordi Pujadas Josep Maria Casas Josep Anton Muñoz Francese Sabat 《Geodinamica Acta》2013,26(3):195-206
AbstractThe structure of the southern Pyrenees, east of the Albanyà fault (Empordà area), consists of several Alpine thrust sheets. From bottom upwards three main structural units can be distinguished : the Roc de Frausa, the Biure-Bac Grillera and the Figueres units. The former involves basement and Paleogene cover rocks. This unit is deformed by E-W trending kilometric-scale folds, its north dipping floor thrust represents the sole thrust in this area. The middle unit is formed by an incomplete Mesozoic succession overlain by Garumnian and Eocene sediments. Mesozoic rocks internal structure consists of an imbricate stack. The floor thrust dips to the south and climbs up section southwards. The upper unit exibits the most complete Mesozoic sequence. Its floor thrust is subhorizontal. The lower and middle units thrust in a piggy-back sequence. The upper unit was emplaced out of sequence.Lower Eocene sedimentation in the Biure-Bac Grillera unit was controlled by emergent imbricate thrusts and synchronic extensional faults. One of these faults (La Salut fault) represents the boundary between a platform domain in the footwall and a subsident trough in the hangingwall. Southward thrust propagation produces the inversion of these faults and the development of cleavage-related folds in their hangingwalls (buttressing effect). This inversion is also recorded by syntectonic deposits, which have been grouped in four depositional sequences. The lower sequences represent the filling on the hangingwall trough and the upper sequences the spreading of clastics to the south once the extensional movement ends. 相似文献