Spectral variations of DY Cen

Two high resolution spectra of the hot RCrB star DY Cen in the red region are compared. The photospheric absorption lines show a radial velocity variation of 12 kms-1 between 1989 July and 1992 May. Emission components to some CII lines present in 1989 are almost entirely absent in 1992. Nebular forbidden lines of [OI], [NII] and [SII] appear unchanged from 1989 to 1992     

Origin and evolution of the Steamboat Springs siliceous sinter deposit, Nevada, U.S.A.

Siliceous hot spring deposits from Steamboat Springs, Nevada, U.S.A., record a complex interplay of multiple, changing, primary environmental conditions, fluid overprinting and diagenesis. Consequently these deposits reflect dynamic geologic and geothermal processes. Two surface sinters were examined—the high terrace, and the distal apron-slope, as well as 13.11 m (43 ft) of core material from drill hole SNLG 87-29. The high terrace sinter consists of vitreous and massive-mottled silica horizons, while the distal deposit and core comprise dominantly porous, indurated fragmental sinters. Collectively, the three sinter deposits archive a complete sequence of silica phase diagenetic minerals from opal-A to quartz. X-ray powder diffraction analyses and infrared spectroscopy of the sinters indicate that the distal apron-slope consists of opal-A and opal-A/CT mineralogy; the core yielded opal-A/CT and opal-CT with minor opal-A; and the high terrace constitutes opal-C, moganite, and quartz. Mineralogical maturation of the deposit produced alternating nano–micro–nano-sized silica particle changes. Based on filament diameters of microbial fossils preserved within the sinter, discharging thermal outflows fluctuated between low-temperatures (< 35 °C, coarse filaments) and mid-temperatures ( 35–60 °C, fine filaments). Despite transformation to quartz, primary coarse and fine filaments were preserved in the high terrace sinter. AMS ¹⁴C dating of pollen from three horizons within core SNLG 87-29, from depths of 8.13 to 8.21 m (26′8″ to 26′11″), 10.13 to 10.21 m (33′3″ to 33′6″), and 14.81 to 14.88 m (48′7″ to 48′10″), yielded dates of 8684 ± 64 years, 11,493 ± 70 years and 6283 ±60 years, respectively. In the upper section of the core, the stratigraphically out-of-sequence age likely reflects physical mixing of younger sinter with quartzose sinter fragments derived from the high terrace. Within single horizons, mineralogical and morphological components of the sinter matrix were spatially patchy. Overall, the deposit was modified by sub-surface flow of alkali-chloride thermal fluids depositing a second generation of silica, and periodically, by acidic steam condensate formed during periods when the water table was low. Local faulting produced considerable fracturing of the sinter. Hence, the Steamboat Springs sinter experienced a complex history of primary and secondary hydrothermal, geologic and diagenetic events, and their inter-relationships and effects are locked within the physical, chemical and biological signatures of the deposit.     

Occurrence and evolution of the Xiaotangshan hot spring in Beijing, China

Thermal groundwater occurs in bedrock aquifers consisting of the dolomite of the Wumishan Group of the Jixianin System and the Cambrian carbonate in the Xiaotangshan geothermal field near the northern margin of the North China Plain, China. The hot water in the geothermal field of basin-type discharges partly in the form of the Xiaotangshan hot spring under natural conditions. The hot water has TDS of less than 600 mg/L and is of Na·Ca-HCO₃ type. The geothermal water receives recharge from precipitation in the mountain area with elevation of about 500 m above sea level to the north of the spring. Thermal groundwater flows slowly south and southeast through a deep circulation with a residence time of 224 years estimated with the Ra–Rn method. The Xiaotangshan hot spring dried up in the middle of the 1980s owing to the increasing withdrawal of the hot water in the geothermal field in the past decades. The water level of the geothermal system still falls continually at an annual average rate of about 2 m, although water temperature changes very little, indicating that the recharge of such a geothermal system of basin-type is limited. Over-exploitation has a dramatic impact on the geothermal system, and reduction in exploitation and reinjection are required for the sustainable usage of the hot water.     

西藏搭格架热泉型铯矿床矿物学与矿石组构特征及地质意义

在查明搭格架铯矿床产出的地质背景、成矿阶段及其年龄、地球化学与同位素组成的基础上,本文较为系统地研究了硅华的矿物学与组构特征,加深了对硅华形成演化过程的认识.研究表明成矿早期,矿石中存在大量的石英,晚期全为蛋白石.粒状蛋白石自早到晚均有出现,胶状蛋白石主要出现于晚期.早期矿石出现脱水造成的菜花状、粗粒块状与粗大孔隙状构造及溶蚀结构.晚期出现细粒块状与细小孔隙状构造.在第3阶段存在硅藻Denticula属,体现出低温阶段的特征.由早到晚,矿石的SiO2呈降低趋势,而(Na2O Al2O3 K2O CaO)与Cs2O呈升高趋势,是随着矿石中SiO2有序度的降低而其它成分被保留在晶格中所致.     

First results from the North Iceland experiment

Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system.     

云南会泽铅锌矿喷流沉积成因研究

会泽铅锌矿床的成因认识各异,曾认为是沉积—改造层控型矿床。研究前人资料、结合亲历找矿实践,讨论该矿床另一种不同的成矿方式。研究矿床地质、地球化学、同位素组成、包裹体、方铅矿年龄测定和成矿温度测试等表明:会泽铅锌矿属海底热卤水喷流沉积—改造层控型矿床,与芒特—艾萨型热卤水喷流沉积层控矿床类似。     

1999年台湾7.6级大震与江苏-南黄海地区中强震预测

分析讨论了台湾地区7级大震与本区中强震之间相关关系，指出1999年台湾7.6级大震后2－3年内，本区将有5－6级中强震发生。同时应用可公度模型和“带头地震”的异年倍九法联合对本区中强震发震时间进行分析预测。结论表明，该方法可以较好地应用于本区短临地震预报实践。     

巴彦浩特盆地火成岩的综合地球物理解释

采用综合地球物理方法识别巴彦浩特盆地火成岩,首先利用高精度重磁资料和大地电磁测深资料,初步确定火成岩的平面位置和深度,然后利用钻遇火成岩的已知测井资料,建立人工合成地震记录,在地震剖面上标定出火成岩并分析其波组特征,采用BP神经网络进行火成岩的精细识别.研究表明,综合地球物理解释是提高反演解释精度的有效途径.     

用航空POLDER测量仪获取的方向性信息增强对北方森林冠层的识别(英文)

ＰＯＬＤＥＲ（地球反射极化和方向）仪器在ＢＯＲＥＡＳ实验中曾搭载ＮＡＳＡ的一架Ｃ１３０飞机飞行。在ＢＯＲＥＡＳ的南部地区，ＰＯＬＤＥＲ获取了各种实验场地上的ＢＲＤＦ测量值。森林覆盖地区的大的热点特征，以及十个地区上的镜面反射分量得到了描述。该文通过ＰＯＬＤＥＲ的测量数据，对向常规的光谱特征中加入通过遥感获得的方向性特征后，对各种森林覆盖的分类和区分能力的提高给出了定量化的解。当将方向信息加入常规光谱信息后，采用无监督分类时，类间耦合矩阵的各项显著减小（减小倍数为２－５倍）。这一事实证明了用遥感方向特征可以增强对ＢＯＲＥＡＬ森林覆盖的区分能力。