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151.
湿斜压大气中暴雨中尺度系统发展的一种可能机制 总被引:1,自引:0,他引:1
根据暴雨中尺度系统发生时的大气运动特征,在绝热、无摩擦条件下,从湿斜压原始方程出发,考虑大气运动的涡度及散度演化不仅受动力场的制约,而且还受到热力场的约束,采用不同于传统研究涡度及散度方程的分析方法,导出了新形式的涡度及散度方程。在此基础上,分析了湿斜压大气中对流层中低层气流旋转与辐合持续增长的动力特征,初步揭示了湿斜压大气中暴雨中尺度系统发展的动力机制。 相似文献
152.
Fabrizio Tursi Richard Spiess Vincenzo Festa Rosa Anna Fregola 《Journal of Metamorphic Geology》2020,38(7):771-793
Linking the deformation history of mylonitized continental rocks to the progress of devolatilization reactions that trigger reaction softening is critical for the understanding of crustal scale processes. We have analysed the field geometries and microstructures of deformed rocks within the southern Hercynian belt in Calabria, as well as modelled the pressure–temperature–deformation (P–T–d) trajectory of a main ductile shear zone that tectonically coupled the deeper crustal Mammola Paragneiss Unit with the upper crustal Stilo–Pazzano Phyllite Unit. P–T modelling of the mylonitic Mammola Paragneiss Unit was performed through calculation of phase equilibrium diagrams with the software thermocalc in the MnNCKFMASHTO model system. The prograde P–T–d trajectory is based on the zoning profiles of garnet porphyroblasts and their mineral inclusions, primarily barroisite and epidote. P–T modelling shows that peak metamorphic conditions of ~0.9 GPa and 585°C were reached during a Dn-1 under-thrusting event. The following exhumation during the Dn mylonitic event, and contact metamorphism during Dn+1 and Dn+2 folding events, have also been modelled because they are essential to restore the previous tectono-metamorphic history. The exhumation trajectory was modelled down to 0.3 GPa with temperatures of 440–460°C, under fluid-deficient conditions, as well as the final late Carboniferous contact metamorphism up to Tmax of 680–720°C. The prograde path shows clear evidence for thermal buffering during garnet growth at the expense of chlorite, with a heating-dominated stage after chlorite breakdown. Subsequently, a rheological change associated with epidote breakdown (i.e. reaction softening) occurred, highlighted by a net steepening of the P/T trajectory towards the pressure peak. On the basis of the barroisite inclusions within garnet porphyroblasts as well as the ‘hairpin’ shape of the reconstructed P–T–d path (before contact metamorphism), we infer that the unusual low T/P gradient for the Hercynian crust exposed in the Mammola Paragneiss Unit records its involvement in the Palaeotethys–Gondwana subduction beneath Laurussia during Dn-1 under-thrusting. We present a new palaeotectonic interpretation along the southern Hercynian belt in Calabria during the Upper Mississippian–Lower Pennsylvanian, that is consistent with previous geochronology studies. 相似文献
153.
介绍了以乙烯底油的HK-200℃馏分油为原料,用一种新配方的三氯化铝催化剂进行催化聚合,制取优质汽油的方法;对催化聚合反应的工艺条件进行了大量的实验研究,探索出生产中各种最佳的工艺参数,为中小型石油化工企业提供了一条经济效益显著的乙烯底油的综合利用途径。 相似文献
154.
155.
Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees
of embrittlement during exhumation, depending on the extent to which fluid–rock reactions proceeded. At one site, graphitic
schists preserve textural evidence for two metamorphic reactions that modified
and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction
involved net consumption of increasingly CO2-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I microcracks. Fluid inclusion arrays
within the microcracks show that increased from ∼0.1 to 0.6 during decompression from 4.75 to 2 kbar at a reference temperature of 500°C. Titanite consumption
is most pronounced within transgranular Mode I microcracks, but microcracks do not crosscut products of this reaction; fluid
consumption during reaction was coeval with the end of microcracking, at least on a local scale. At the other site, graphitic
schists lack small-scale Mode I cracks as well as evidence for graphite consumption during decompression. SEM imaging shows
that graphite is anhedral and pitted at the first site, but occurs in clusters of euhedral grains at the second site. Mass
balance calculations demonstrate that rocks with partially consumed graphite were infiltrated by an externally derived, H2O-rich fluid that drove subsequent graphite-fluid reaction. Evidence for similar fluid infiltration is absent at the second
site. Variations in the degree of reaction progress indicate that fluid pathways and deformation style were heterogeneous
on the scale of millimeters to kilometers during exhumation from mid-crustal depths. 相似文献
156.
P. J. O'BRIEN 《Journal of Metamorphic Geology》2008,26(2):235-251
High‐pressure granulites are an important record of geodynamic processes in overthickened or subducted continental crust. Orthopyroxene‐free assemblages in granitic (ternary feldspar(s) + quartz + garnet + kyanite + rutile), intermediate (ternary feldspar(s) + quartz + garnet + clinopyroxene ± kyanite ±rutile ± titanite) and basic (garnet + clinopyroxene + plagioclase ± quartz + rutile) compositions indicate formation conditions at mantle depths. Clinopyroxene compositions in Variscan high‐pressure granulites are unusual in that they include omphacite (in plagioclase‐bearing rocks thus not eclogite) and Al‐rich diopside (i.e. indicating high Ca‐Tschermak content), with both yielding temperatures above 900 °C. Problems such as compositional zoning, multiple generations of key phases in reaction domains and unmixing of high‐temperature solid‐solution phases during cooling (ternary feldspars, omphacite) clearly indicate disequilibrium and require very careful interpretation as to which phases and compositions possibly represent a former equilibrium association. Pressure–temperature (P–T) determination by the pseudosection method, although allowing prediction of mineral assemblages, compositions and molar proportions for a fixed bulk composition for modelled P–T conditions, still requires reliable activity–composition information for the key phases feldspar and clinopyroxene as well as an interpretation of former equilibrium compositions in the investigated samples, i.e. the same restrictions applying to conventional thermobarometry. The interpretations of some recently determined pseudosections for the composition of Variscan clinopyroxene‐bearing high‐pressure granulites contradict numerous published P–T paths. However, quantitative information from thermobarometry or pseudosections must be integrated with key petrographic observations. In the case of the Variscan example, it is argued that petrographic observations and published P–T paths are consistent with mineral assemblages predicted in pseudosections and support existing tectonometamorphic models. 相似文献
157.
158.
本文根据物理化学基本原理,提出HF的表面吸附催化机制对于CaF2-HCl-H2O固-液反应体系溶解振荡起着关键性作用。同时建立了该 体系的动力学模型,研究其振荡现象的非线性动力学起因,虽然这一数学模型是基于CSTR反应器为对象而建立的,不过其基本的结论对叠层式流动反应器的情况也是适用的。 相似文献
159.
Partial transformation of gabbro to coesite-bearing eclogite from Yangkou, the Sulu terrane, eastern China 总被引:18,自引:2,他引:18
An ultra-high-pressure (UHP) metamorphic slab at Yangkou Beach near Qingdao in the Sulu region of China consists of blocks of eclogite facies metagabbro, metagranitoid, ultramafic rock and mylonitic orthogneisses enclosed in granitic gneiss. A gradational sequence from incipiently metamorphosed gabbro to completely recrystallized coesite eclogite formed at ultra-high-pressures was identified in a single 30 m block; metagabbro is preserved in the core whereas coesite eclogite occurs along the block margins. The metagabbro contains an igneous assemblage of Pl+Aug+Opx+Qtz+Bt+Ilm/Ti-Mag; it shows relict magmatic textures and reaction coronas. Fine-grained garnet developed along boundaries between plagioclase and other phases; primary plagioclase broke down to Ab+Ky+Ms+Zo±Grt±Amp. Augite is rimmed by sodic augite or omphacite, whereas orthopyroxene is rimmed by a corona of Cum±Act and Omp+Qtz layers or only Omp+Qtz. In transitional rocks, augite and orthopyroxene are totally replaced by omphacite, and the lower-pressure assemblage Ab+Ky+Phn+Zo+Grt coexists with domains of Omp (Jd70–73)+Ky±Phn in pseudomorphs after plagioclase. Both massive and weakly deformed coesite-bearing eclogites contain Omp+Ky+Grt+Phn+Coe/Qtz+Rt, and preserve a faint gabbroic texture. Coesite inclusions in garnet and omphacite exhibit limited conversion to palisade quartz; some intergranular coesite and quartz pseudomorphs after coesite also occur. Assemblages of the coronal stage, transitional and UHP peak occurred at about 540±50 °C at c. 13 kbar, 600–800 °C at ≥15–25 kbar and 800–850 °C at >30 kbar, respectively. Garnet from the coronal- through the transitional- to the eclogite-stage rocks show a decrease in almandine and an increase in grossular±pyrope components; garnet in low-grade rocks contains higher MnO and lower pyrope components. The growth textures of garnet within pseudomorphs after plagioclase or along grain boundaries between plagioclase and other phases are complex; the application of garnet zoning to estimate P–T should be carried out with caution. Some garnet enclosing quartz aggregates as inclusions shows radial growth boundaries; these quartz aggregates, as well as other primary and low-P phases, persisted metastably at UHP conditions due to sluggish reactions resulting from the lack of fluid during prograde and retrograde P–T evolution. 相似文献
160.
我们首次在湖南发现了钾镁煌斑岩。这套岩石由于遭受强烈风化和蚀变,与典型的西澳钾镁煌斑岩相比,其K_2O和MgO含量明显偏低,Al_2O_3含量偏高。REE含量、金云母成分及以金云母作为主要载体的元素(如Rb、Ba、Ti、Sc、Zn、Ga和Nb等)都与西澳的钾镁煌斑岩基本一致,此外高度富集LREE和U,Th、Nb、Ta、Zr等不相容元素,并有高的δ~(18)O‰值,表明形成这套岩石的上地幔源区受到了软流圈的交代作用。 相似文献