极低饱和度和近饱和状态下海水中方解石和文石溶解动力学研究

利用free-drift开放反应系统,在恒压力(101.325 kPa)和恒温度(25.0±0.2)℃环境条件下,研究人工海水中二氧化碳分压(pCO2)的变化对方解石和文石的溶解速率及反应级数的影响.研究结果表明:如果溶解实验中pCO2未达到完全平衡,计算得出的反应级数偏小,且反应液pCO2不平衡是造成不同反应阶段反应...     

二氧化碳羽流地热系统水-岩-气相互作用:以松辽盆地泉头组为例

二氧化碳羽流地热系统(CPGS)是利用CO2地质储存场地进行地热能开发的一种工程技术,也是整合CO2减排与开发深部地热资源的理想方式。但伴随着对深部地热的提取,注入储层的超临界CO2使深部咸水的pH值降低,导致周围岩体产生溶解和沉淀,从而引起孔隙度、渗透率等地层物性的变化,最终改变系统的生产能力和净热提取效率。以松辽盆地泉头组为目标储层,采用室内实验、数值模拟等技术手段,通过实验和数值计算结果的对比,揭示系统水-岩-气相互作用对热储矿物组分的改变。研究结果显示:实验过程中矿物溶解对温度和盐度变化较为敏感,而受压力影响较小;在实验和模拟时间内发生溶解的矿物主要是长石类矿物,方解石在反应后全部溶解;石英、伊利石和高岭石的矿物组分体积分数有所增加,并有少量菱铁矿生成。     

High-pressure granulites in the Sanggan area, North China craton: metamorphic evolution, P–T paths and geotectonic significance

High‐pressure basic granulites are widely distributed as enclaves and sheet‐like blocks in the Huaian TTG gneiss terrane in the Sanggan area of the Central Zone of the North China craton. Four stages of the metamorphic history have been recognised in mineral assemblages based on inclusion, exsolution and reaction textures integrated with garnet zonation patterns as revealed by compositional maps and compositional profiles. The P–T conditions for each metamorphic stage were obtained using thermodynamically and experimentally calibrated geothermobarometers. The low‐Ca core of growth‐zoned garnet, along with inclusion minerals, defines a prograde assemblage (M1) of garnet + clinopyroxene + plagioclase + quartz, yielding 700 °C and 10 kbar. The peak of metamorphism at about 750–870 °C and 11–14.5 kbar (M2) is defined by high‐Ca domains in garnet interiors and inclusion minerals of clinopyroxene, plagioclase and quartz. Kelyphites or coronas of orthopyroxene + plagioclase ± magnetite around garnet porphyroblasts indicate garnet breakdown reactions (M3) at conditions around 770–830 °C and 8.5–10.5 kbar. Garnet exsolution lamellae in clinopyroxene and kelyphites of amphibole + plagioclase around garnet formed during the cooling process at about 500–650 °C and 5.5–8 kbar (M4). These results help define a sequential P–T path containing prograde, near‐isothermal decompression (ITD) and near‐isobaric cooling (IBC) stages. The clockwise hybrid ITD and IBC P–T paths of the HP granulites in the Sanggan area imply a model of thickening followed by extension in a collisional environment. Furthermore, the relatively high‐pressures (6–14.5 kbar) of the four metamorphic stages and the geometry of the P–T paths suggest that the HP granulites, together with their host Huaian TTG gneisses, represent the lower plate in a crust thickened during collision. The corresponding upper‐plate might be the tectonically overlying Khondalite series, which was subjected to medium‐ to low‐pressure (MP/LP: 7–4 kbar) granulite facies metamorphism with a clockwise P–T path including an ITD segment. Both the HP and the MP/LP granulite facies events occurred contemporaneously at c. 1.90–1.85 Ga in a collisional environment created by the assembly process of the North China craton.     

Solving the graceful exit problem in superstring cosmology

We briefly review the status of the “graceful exit” problem in superstring cosmology and present a possible resolution. It is shown that there exists a solution to this problem in two-dimensional dilaton gravity provided quantum corrections are incorporated. This is similar to the recently proposed solution of Rey. However, unlike in his case, in our one-loop corrected model the graceful exit problem is solved for any finite number of massless scalar matter fields present in the theory.     

砂岩型铀矿成矿过程中腐殖酸的化学作用

研究表明,腐殖酸在铀成矿过程中的化学作用受多种因素制约,如pH值、温度和离子强度等。由于腐殖酸和富啡酸结构中的一些单元与一些小分子的芳香有机酸相似,因此,利用小分子的芳香有机酸来代替腐殖酸,研究不同条件下腐殖酸对铀成矿的影响,并获得了不同形式铀的配合物,证明了铀在含腐殖酸环境中的赋存状态。     

Collapse Velocity and Prompt Explosion for the Presupernova Model Ws15M⊙

For the presupernova model Wsl5M⊙, we re-calculate the electron capture (EC) timescale and hydrodynamical (HD) timescale. We found that the EC timescale can be smaller than the HD timescale in the inner region of the collapse iron core at the moment immediately before the shock wave bounce. The change in these two timescales at the late stage of core collapse is expected to affect the collapse velocity. If the late-time collapse velocity is artificially increased by a small quantity, then prompt explosion of the supernova may happen. Further calculations are still needed to check the plausibility of the acceleration mechanism caused by the faster EC process.     

Metamorphic processes: a celebration of the career contribution of Ron Vernon

This Special Issue is in celebration of the career contribution of Ron Vernon. It arises from the ‘Ron Vernon Symposium’, which was held as part of the 15th Australian Geological Convention in Sydney in 2000. To date Ron has published more than one hundred scientific papers, several books and contributed widely to international conferences. He is the doyen in the multidisciplinary field of microstructures, which spans petrology and structural geology. However, Ron's range is phenomenal, and he has contributed to many aspects of metamorphism, magmatism and rock deformation. He has drawn on data from his work in these areas to contribute widely to understanding thermal regimes, crustal evolution and tectonics, as exemplified by his ideas about HTLP metamorphism and emplacement of granites. Ron has followed the scientific method in his work; it has led him to many innovative interpretations, some of which undermined established dogma. By example, Ron has been a positive role model for the younger generation. However, for the older generation, he has been something of a bête noire! The papers in this Special Issue cover the range from low‐ to high‐grade metamorphism, from metasomatism to melting, from microstructures to tectonics, and from fieldwork to experiments. It is our hope that in reading them you will take time to think about what has been achieved in the past 40 years, and use this as motivation for what remains to be done.     

壳型剪切带中金矿预测参数

本文设想把华北陆台北缘前寒武纪变质岩区韧性剪切变形-变质带中金矿成矿作用做为区域变质作用-构造作用-岩浆作用旋回中的一部分。这类金矿主要形成在这一旋回的晚期,变质地质体被抬升的阶段,并就位于低温韧-脆性变形变质带中,属于各种内动力地质作用的综合产物。分析韧性剪切变形-变质带(DDMZ)内金矿成矿过程中的这种多因素、多阶段的各种信息,我们提出如下参数:区域性参数富铁质变质岩石组合和壳型剪切带;最佳区段参数—低温韧-脆性变形-变质带和弱碱性钾质花岗岩;金矿化带参数—岩石-流体交代带。其目的是明确找矿目标,提高金矿预测有效性。