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91.
92.
通过对塔东地区古城4井上寒武统和中、上奥陶统碳酸盐岩围岩及充填物的碳、氧、锶同位素地球化学和流体包裹体成分的对比研究表明,充填于中、上奥陶统和上寒武统的流体分属于2个不同来源的流体体系。充填于中、上奥陶统灰岩裂缝中方解石脉的w(87Sr)/w(86Sr)介于0.7084~0.7088,它与早奥陶世海水的w(87Sr)/w(86Sr)相近;流体体系为CH4-H2O体系;充填物与围岩间具有明显的碳、氧同位素差异,表明上部流体体系中的流体来自于奥陶系地层本身。上寒武统白云岩裂缝中方解石脉的w(87Sr)/w(86Sr)为0.7138,明显地高于同时代海水的锶同位素值;流体体系为CO2-H2O体系;下部流体体系中的流体为外来富锶流体。上、下流体体系间互不连通暗示着上寒武统地层具有相对较好的保存条件。 相似文献
93.
Early carbonate cements in the Yanchang Formation sandstones are composed mainly of calcite with relatively heavier carbon isotope (their δ^18O values range from -0.3‰- -0.1‰) and lighter oxygen isotope (their δ^18O values range from -22.1‰- -19.5‰). Generally, they are closely related to the direct precipitation of oversaturated calcium carbonate from alkaline lake water. This kind of cementation plays an important role in enhancing the anti-compaction ability of sandstones, preserving intragranular volume and providing the mass basis for later disso- lution caused by acidic fluid flow to produce secondary porosity. Ferriferous calcites are characterized by relatively light carbon isotope with δ^13C values ranging from -8.02‰ to -3.23‰, and lighter oxygen isotope with δ^18O values ranging from -22.9‰ to -19.7‰, which is obviously related to the decarboxylation of organic matter during the late period of early diagenesis to the early period of late diagenesis. As the mid-late diagenetic products, ferriferous cal- cites in the study area are considered as the characteristic authigenic minerals for indicating large-scaled hydrocarbon influx and migration within the clastic reservoir. The late ankerite is relatively heavy in carbon isotope with δ^13C values ranging from -1.92‰ to -0.84‰, and shows a wide range of variations in oxygen isotopic composition, with δ^18O values ranging from -20.5‰ to -12.6‰. They are believed to have nothing to do with decarboxylation, but the previously formed marine carbonate rock fragments may serve as the chief carbon source for their precipitation, and the alkaline diagenetic environment at the mid-late stage would promote this process. 相似文献
94.
Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance of the fracture-cavity reservoir bed from the top of the section. The seismic reflection becomes weak or is absent when the fracture-cavity reservoir beds are less than 20 ms below the top Ordovician. The effect on top Ordovician reflection became weaker with deeper burial of fracture-cavity reservoir beds but the developed deep fracture-cavity reservoir beds caused stronger reflection in the interior of the Ordovician. This interior reflection can be divided into strong long-axis, irregular and bead string reflections, and was present 80 ms below the top Ordovician. Aimed at understanding reflection characteristics, the spectral decomposition technique, which uses frequency to "tune-in" bed thickness, was used to predict Ordovician fracture-cavity carbonate formations in the Tahe oilfield. Through finely adjusting the processing parameters of spectral decomposition, it was found that the slice at 30 Hz of the tuned data cube can best represent reservoir bed development. Two large N-S-trending strong reflection belts in the mid-western part of the study area along wells TK440- TK427-TK417B and in the eastern part along wells TK404-TK409 were observed distinctly on the 30 Hz slice and 4-D time-frequency data cube carving. A small N-S trending reflection belt in the southern part along wells T403-TK446B was also clearly identified. The predicted reservoir bed development area coincides with the fracture-cavities connection area confirmed by drilling pressure testing results. Deep karst cavities occur basically in three reservoir bed-development belts identified by the Ordovician interior strong reflection. Spectral decomposition proved to be a useful technique in identifying fracture-cavity reservoir beds. 相似文献
95.
96.
GPS observations of the ionospheric F2-layer behavior during the 20th November 2003 geomagnetic storm over South Korea 总被引:4,自引:1,他引:3
The ionospheric F2-layer peak density (NmF2) and its height (hmF2) are of great influence on the shape of the ionospheric
electron density profile Ne (h) and may be indicative of other physical processes within the ionosphere, especially those
due to geomagnetic storms. Such parameters are often estimated using models such as the semiempirical international reference
ionosphere (IRI) models or are measured using moderately priced to expensive instrumentation, such as ionosondes or incoherent
scatter radars. Global positioning system (GPS) observations have become a powerful tool for mapping high-resolution ionospheric
structures, which can be used to study the ionospheric response to geomagnetic storms. In this paper, we describe how 3-D
ionospheric electron density profiles were produced from data of the dense permanent Korean GPS network using the tomography
reconstruction technique. These profiles are verified by independent ionosonde data. The responses of GPS-derived parameters
at the ionospheric F2-layer to the 20th November 2003 geomagnetic storm over South Korea are investigated. A fairly large
increase in the electron density at the F2-layer peak (the NmF2) (positive storm) has been observed during this storm, which
is accompanied by a significant uplift in the height of the F2 layer peak (the hmF2). This is confirmed by independent ionosonde
observations. We suggest that the F2-layer peak height uplift and NmF2 increase are mainly associated with a strong eastward
electric field, and are not associated with the increase of the O/N2 ratio obtained from the GUVI instruments aboard the TIMED satellite. It is also inferred that the increase in NmF2 is not
caused by the changes in neutral composition, but is related to other nonchemical effects, such as dynamical changes of vertical
ion motions induced by winds and E × B drifts, tides and waves in the mesosphere/lower thermosphere region, which can be dynamically
coupled upward to generate ionospheric perturbations and oscillations. 相似文献
97.
98.
在夏季分层期间对红枫湖南、北湖湖心的水样进行分层采集,同时测定了分层水样的温度、pH、HCO3-浓度、溶解氧(DO)、叶绿素a(Chl-a)及铵根离子(NH4+)、硝酸根离子(NO3-)、磷酸根离子(PO43-)的浓度,水体中CO2的分压(pCO2)由化学平衡及亨利定律求得。研究结果表明:光合作用、有机质降解及水体热分层是影响红枫湖夏季pCO2分布的主要因素。其中,温水层CO2欠饱和是光合作用吸收CO2引起的,温跃层中pCO2的急剧增加是光合产物降解产生CO2引起的。静水层沉积物附近pCO2最高并且还有持续增加的趋势,说明沉积物中有机质降解是静水层中CO2增加的主要原因,夏季湖底水温较高加快了沉积物中有机质的降解。分层现象使pCO2在水体中的分布差别明显,并且使静水层中CO2得到积累。此外,夏季红枫湖水体中pCO2的变化与NH4+、PO43-的变化密不可分,表现为温水层中光合作用消耗NH4+、PO43-,有机质降解过程伴随NH4+、PO43-的释放。 相似文献
99.
采用溶胶低温燃烧法和高温固相反应法制备了锶掺杂的正铌酸镧(La0.95Sr0.05NbO4)超细陶瓷粉体。应用XRD、SEM和激光粒度分析仪等对陶瓷粉体的物相、粒度和粒度分布进行了表征,同时考察了两种方法制备的粉体的烧结性能。结果表明:采用溶胶低温燃烧法制备的La0.95Sr0.05NbO4(LSNb)为粒径〈100 nm、粒度分布范围窄的超细粉体;高温固相反应法制备的粒径为0.5-1.0μm、呈球形的LSNb超细陶瓷粉体。溶胶低温燃烧法制备的粉体在1 250℃烧结10 h形成致密的陶瓷片;高温固相反应法制备的粉体在1 400℃以上烧结10 h致密。两种LSNb致密膜均具有一定的透氢作用,900℃氢渗速率分别为1.96×10^-3mL·cm^-2·min^-1和1.67×10^-3mL·cm^-2·min^-1。 相似文献
100.
Takeshi Ohno Tsuyoshi Komiya Yuichiro Ueno Takafumi Hirata Shigenori Maruyama 《Gondwana Research》2008,14(1-2):126
We measured both mass-dependent isotope fractionation of δ88Sr (88Sr/86Sr) and radiogenic isotopic variation of Sr (87Sr/86Sr) for the Neoproterozoic Doushantuo Formation that deposited as a cap carbonate immediately above the Marinoan-related Nantuo Tillite. The δ88Sr and 87Sr/86Sr compositions showed three remarkable characteristics: (1) high radiogenic 87Sr/86Sr values and gradual decrease in the 87Sr/86Sr ratios, (2) anomalously low δ88Sr values at the lower part cap carbonate, and (3) a clear correlation between 87Sr/86Sr and δ88Sr values. These isotopic signatures can be explained by assuming an extreme greenhouse condition after the Marinoan glaciation. Surface seawater, mixed with a large amount of freshwater from continental crusts with high 87Sr/86Sr and lighter δ88Sr ratios, was formed during the extreme global warming after the glacial event. High atmospheric CO2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87Sr/86Sr and lighter δ88Sr ratios. Subsequently, the mixing of the underlying seawater, with unradiogenic Sr isotope compositions and normal δ88Sr ratios, probably caused gradual decrease of the 87Sr/86Sr ratios of the seawater and deposition of carbonate with normal δ88Sr ratios. The combination of 87Sr/86Sr and δ88Sr isotope systematics gives us new insights on the surface evolution after the Snowball Earth. 相似文献