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161.
162.
华南晚古生代礁硅岩套的组成和分类及地质涵义 总被引:4,自引:0,他引:4
礁硅岩套是一种重要的含矿岩石组合,它是由生物礁相碳酸盐岩、热水沉积岩(矿)、细碎屑岩和泥灰岩、同怪位或相邻地区地层中的火山质岩或潜火山岩,以较为固定的时空有序的状态组合而成。根据生物礁的形成环境和热水沉积作用的产出方式,礁硅岩套可分为盆地型、台地型和过渡型三类。它是在特征地质背景下,在盆地演化的一定阶段内,由盆地正常沉积作物、盆地中的生物作用、盆下源的热水沉积作用和岩石圈深部岩浆作用综合形成的产物 相似文献
163.
An experimental study of the solubility of Pt and Pd sulfides and Au metal in aqueous bisulfide solutions was conducted at temperatures from 200° to 350 °C and at saturated vapor pressure. A 500-mL Bridgemantype pressure vessel constructed of titanium, and equipped with a motor-driven magnetic stirrer was employed. The pH and the oxidation state were buffered by the coexistence of H2S/HS–/SO
inf4
sup2–
. The pH at temperature was calculated to be in the range 5.91–9.43, and S was 0.3–2.2 m. Under the experimental conditions, the measured solubility of gold is about two to three orders of magnitude greater than that of either platinum and palladium, and the measured solubility of platinum is, in general, approximately equal to that of palladium, in molal units. The solubilities are found to be in the range: platinum 4–800 ppb, palladium 1–400 ppb, and gold 2–300 ppm. The solubility data can be modeled adequately using the following reactions: Au+H2S+HH–=Au(HS)
2
–
+1/2H2 (K14); PtS+HS–+H+=Pt (HS)
2
0
(K15); PdS+HS–+H+=Pd (HS)
2
0
(K16); PtS2+H2=Pt (HS)
2
0
(K21).With equilibrium constants determined as follows (errors represent two standard deviations): Preliminary measurements of the solubilities of metallic Pt, Pd and Au as hydroxide complexes were also conducted using a second titanium pressure vessel, at temperatures of 200° to 350 °C and vapor saturation pressure, with pH and the oxidation state controlled or buffered by adding known amounts of NaOH and H2 gas. The concentration of NaOH was in the range 0.01–1.3 m, and the partial pressure of H2 at 200 °C was 62–275 bars, initially. Under the temperature and pressure conditions of these experiments, the solubility of platinum in 1 m NaOH solution is less than 100 ppb, that of palladium is less than 10 ppb and that of gold is less than 0.2 ppm; and in 0.01 m NaOH solutions, both Pt and Pd solubilities are less than 1 ppb. These data indicate that the contributions of hydroxide complexes to the total solubilities in the bisulfide runs, where the pH was in the range of 5.9–9.4, are negligible. The concentrations of both Pt and Pd as bisulfide complexes in the Salton Sea geothermal system predicted using the stability constants determined in this work agree very well with those values measured by McKibben et al. (1990). This calculation strongly suggests that the PGE are transported in moderately reducing, near neutral hydrothermal fluids as bisulfide complexes, as is gold. However, the much lower maximum solubility of the PGE relative to gold severely constrains models of re genesis, and may explain the relative rarity of hydrothermal PGE deposits compared to the relative abundance of hydrothermal Au deposits. 相似文献
164.
165.
Guan Qing Yu Pan Bao Tian Li NaLi Qiong Zhang JundiGao Hongshan Liu Jia 《Comptes Rendus Geoscience》2010,342(3):189-196
Records of two loess sections located in mid-eastern and western margins of the East Asian Monsoon area captured 20 Dansgaard-Oescher events and six Heinrich events. All these suggested that the climate in the East Asian Monsoon area fluctuated rapidly on millennial to century timescales during the whole Last Glacial. We found that these loess-based events of rapid climate fluctuations were generally synchronous with those of GRIP records, but that there were differences between the Shagou loess section in the west and the Wangguan loess section in the east: the former was more sensitive to climate change than the latter. Compared with earlier studies on loess records covering the Last Glacial from neighboring areas, we discovered that the magnitude of Dansgaard-Oeschger cycles decreased gradually from west to east and we suggest that it resulted from the combined effect of the Westerlies and the East Asian Monsoon. 相似文献
166.
采用在经典离子晶体作用势中附加Morse势 ,并进行必要的量子化修正 ,对石英 α型SiO2 结构随压力变化特性进行分子动力学计算模拟 ,获得了压力高于 2 4 .6GPa ,从晶相向非晶相相变模拟结果 ,并利用其离子间相互作用势、摩尔体积变化、键角等重要信息对模拟结果作了深入的探讨 ,获得了与实验结果较一致的模拟结果。 相似文献
167.
168.
基于长江中游沿岸地质环境条件及过江大桥场地建设基本要求,优选地形地貌、工程地质条件及区域稳定性3个评价因素,运用层次分析法开展长江中游沿岸过江大桥工程场地建设适宜性评价,将长江中游沿岸过江大桥工程分为适宜开发岸线、较适宜开发岸线、一般适宜开发岸线及非优先开发岸线4个等级.长江中游沿岸地区以较适宜开发岸线和一般适宜开发岸线为主,长度分别为625.19 km和598.99 km,分别占岸线总长度的31.35%和30.04%.针对长江中游不同等级岸线的地质特征,提出了相应的地学建议,为长江中游沿岸过江大桥优化选址提供地学指导,进一步促进长江经济带国土资源空间规划与岸线资源保护利用工作的开展. 相似文献
169.
170.
为了揭示地下水由江汉平原周缘向中心径流过程中的水质演化和复杂的水文地球化学作用,以江汉平原西部地区为例,通过数理统计、水化学、同位素地球化学、离子比值关系等方法,开展了江汉平原西部边缘地带浅层孔隙地下水的水文地球化学特征研究。结果表明: 平原区孔隙水以HCO3-Ca·Mg型为主,丘岗区(丘陵和岗地)主要是HCO3-Ca·Mg型,少量为HCO3·SO4-Ca·Mg型,还出现了HCO3·NO3-Ca·Mg型水,总溶解固体(total dissolved solids,TDS)升高主要是由于碳酸盐岩的溶解; 浅层孔隙水均来源于大气降水,蒸发作用对该地区孔隙水的影响较小; 方解石、白云石和石膏的溶解主导研究区的水文地球化学过程,也是孔隙水中Ca2+、Mg2+的主要来源,Na+和K+的主要来源是阳离子交换吸附。 相似文献