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131.
SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neo-proterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857 ± 13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neo-proterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860–750 Ma mantle superplume beneath the supercontinent Rodinia. 相似文献
132.
使用GPS接收机的UTC作为北极星天文方位角测量的时间比对的标准时间,利用推估UTl与UTC的差值,将时间归算到UTl的方法,可满足各等级天文方位角测量的要求,现场计算零点恒星时和北极星坐标的精度满足北极星天文方位角测量的要求,实现了现场评估测量精度。 相似文献
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134.
观测有效性的度量方法 总被引:4,自引:1,他引:4
基于Hilbert空间理论 ,通过对观测方程的系数阵实施格拉姆_施密特 (Gram_Schmidt,G_S)正交化过程 ,分析观测的两个特性 ,从一个新的角度论证了参数估计的必要观测问题 ,以及多余观测与必要观测的关系 ;用欧氏范数‖·‖2 和Frobenius‖·‖ F 范数作为基本度量工具对观测提供参数估计的信息量进行度量分析 ,研究观测的有效性和参数估计的可靠性。采用观测空间分析方法研究了测绘学科中必要观测、多余观测等基本概念 ;提出了观测信息量、观测有效性的概念和相应的度量方法 ;从观测的空间结构出发分析参数估计系统的可靠性 ,从一个侧面扩展和丰富了测绘学中的可靠性理论 ;丰富了研究测绘学中一些基本问题的分析方法 ,也为信息学中的数据挖掘问题提供了一种分析思路 相似文献
135.
地图更新是地图制作过程中常见的,通过对现有数据的编辑和制图综合得到新的地图是一种省时省力、提高工作效率的作业方法。在此过程中,不可避免地会出现老数据和新地图之间不能套准的问题。MicroStation具备了其它绘图软件所不具备的对矢量图形进行纠正的功能,本文就此进行了阐述。 相似文献
136.
ZHANGJin MAZongjin RENWenjun LEIYongliang 《大地构造与成矿学(英文版)》2003,27(1):165-178
There are many thrust-related structures occurring in the Paleozoic strata of the Niushou Mountain in the central part of Ningxia Hui Autonomous Region. The fault-related folds are the typical structures in this area. Based on the analysis about these structures and their relationships, the processes by which these structures of the Miboshan Formation were formed are reconstructed, and the strata underwent about three stages of deformation: (1) horizontal shortening, (2) folding, and (3) thrusting. And the fact that the Niushou Mountain is the leading edge of an old thrust sheet was proved, the Niushou Mountain, the Daluo Mountain and the Xiaoluo Mountain together constitute the front part of this old thrust zone, so the Niushou Mountain and the Ordovician strata in the central and southern parts of Ningxia now are likely allochthons. In the period from middle Ordovician to Devonian, the areas of the central and southern Ningxia belonged to the back-arc foreland basin of North Qilianshan orogen, which was adjacent to the continent in the north. In the later part of the early Paleozoic period, the Niushou Mountain was formed after the closure of the back-arc foreland basin. 相似文献
137.
Shifeng Dai Xiaoqiang Hou Deyi Ren Yuegang Tang 《International Journal of Coal Geology》2003,55(2-4):139-150
The chemical composition of pyrite in coal can be used to investigate its geological and mineralogical origin. In this paper, high-resolution time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the chemical composition of various pyrite forms in the No. 9 coal seam (St,d=3.46%) from the Wuda Coalfield, Inner Mongolia, northern China. These include bacteriogenic, framboidal, massive, cell-filling, fracture-filling, and nodular pyrites. In addition to Fe+ (54Fe+, 56Fe+, 57Fe+), other fragment ions were detected in bacteriogenic pyrites, such as 27Al+, Si+ (28Si+, 29Si+, 30Si+), 40Ca+, Cu+ (63Cu+, 65Cu+), Zn+ (64Zn+, 66Zn+, 67Zn+, 68Zn+), Ni+ (58Ni+, 60Ni+, 62Ni+), and C3H7+. TOF-SIMS images show bacteriogenic pyrites are relatively rich in Cu, Zn, and Ni, suggesting that bacteria probably play an important role in the enrichment of Cu, Zn, and Ni during their formation. Intense positive secondary ion fragments from framboidal aggregates, such as 27Al+, 28Si+, 29Si+, AlO+, CH2+, C3H3+, C3H5+, and C4H7+, indicate that formation of the framboidal aggregates may have occurred together with clay mineral and organic matter, which probably serve as the binding substance. The intense ions of 28Si+ and 27Al+ from massive pyrites also suggest that their pores incorporated clay minerals during crystallization. Together with the lowest 28Si+/23Na+ value, the intense organic positive secondary ion peaks from cell-filling pyrites, such as C3H3+, C3H5+, C3H7+, and C4H7+, indicate that pyrite formation may have accompanied dissolution or disintegration of the cell. The intense P+ peak was observed only in the fracture-filling pyrite and the highest 28Si+/23Na+ value of fracture-filling pyrite reflects its epigenetic origin. Together with XRD and REEs data, the stronger 40Ca+ in nodular pyrite than other pyrite forms shows seawater influence during its formation. 相似文献
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140.
To reconstruct oceanographic variations in the subtropical South Pacific, 271-year long subseasonal time series of Sr/Ca and δ18O were generated from a coral growing at Rarotonga (21.5°S, 159.5°W). In this case, coral Sr/Ca appears to be an excellent proxy for sea surface temperature (SST) and coral δ18O is a function of both SST and seawater δ18O composition (δ18Osw). Here, we focus on extracting the δ18Osw signal from these proxy records. A method is presented assuming that coral Sr/Ca is solely a function of SST and that coral δ18O is a function of both SST and δ18Osw. This method separates the effects of δ18Osw from SST by breaking the instantaneous changes of coral δ18O into separate contributions by instantaneous SST and δ18Osw changes, respectively. The results show that on average δ18Osw at Rarotonga explains ∼39% of the variance in δ18O and that variations in SST explains the remaining ∼61% of δ18O variance. Reconstructed δ18Osw shows systematic increases in summer months (December-February) consistent with the regional pattern of variations in precipitation and evaporation. The δ18Osw also shows a positive linear correlation with satellite-derived estimated salinity for the period 1980 to 1997 (r = 0.72). This linear correlation between reconstructed δ18Osw and salinity makes it possible to use the reconstructed δ18Osw to estimate the past interannual and decadal salinity changes in this region. Comparisons of coral δ18O and δ18Osw at Rarotonga with the Pacific decadal oscillation index suggest that the decadal and interdecadal salinity and SST variability at Rarotonga appears to be related to basin-scale decadal variability in the Pacific. 相似文献