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61.
南海西沙海槽地区的海底热流测量 总被引:20,自引:0,他引:20
为了解南海西沙海槽区的地热特征,利用Ewing型地热探针在该区开展了地热测量,并利用TK04热导率仪测量了相关站位表层沉积物样品的热导率,获得了7个站位的热流数据。结果表明,研究区7个站位的热导率变化范围为0.88~1.06 W/m.K,平均为0.96 W/m.K,地温梯度变化范围为85~120℃/km,热流值变化范围为83~112 mW/m2,平均达到95 mW/m2。分析表明测量结果与20世纪80年代中美合作在西沙海槽的地热测量结果一致性较好,说明研究区仍具有高热流特征,推测高热流特征可能与本区高热背景、莫霍面埋深较浅、断裂发育、晚期岩浆活动和基底起伏等有关。 相似文献
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Quantifying Barrovian metamorphism in the Danba Structural Culmination of eastern Tibet 总被引:3,自引:0,他引:3
O. M. Weller M. R. St‐Onge D. J. Waters N. Rayner M. P. Searle S.‐L. Chung R. M. Palin Y.‐H. Lee X. Xu 《Journal of Metamorphic Geology》2013,31(9):909-935
The Danba Structural Culmination is a tectonic window into the late Triassic to early Jurassic Songpan‐Garzê Fold Belt of eastern Tibet, which exposes an oblique section through a complete Barrovian‐type metamorphic sequence. Systematic analysis of a suite of metapelites from this locality has enabled a general study of Barrovian metamorphism, and provided new insights into the early thermotectonic history of the Tibetan plateau. The suite was used to create a detailed petrographic framework, from which four samples ranging from staurolite to sillimanite grade were selected for thermobarometry and geochronology. Pseudosection analysis was applied to calculate P–T path segments and determine peak conditions between staurolite grade at ~5.2 kbar and 580 °C and sillimanite grade at ~6.0 kbar and 670 °C. In situ U–Pb monazite geochronology reveals that staurolite‐grade conditions were reached at 191.5 ± 2.4 Ma, kyanite‐grade conditions were attained at 184.2 ± 1.5 Ma, and sillimanite‐grade conditions continued until 179.4 ± 1.6 Ma. Integration of the results has provided constraints on the evolution of metamorphism in the region, including a partial reconstruction of the regional metamorphic field gradient. Several key features of Barrovian metamorphism are documented, including nested P–T paths and a polychronic field gradient. In addition, several atypical features are noted, such as P–T path segments having similar slopes to the metamorphic field gradient, and Tmax and Pmax being reached simultaneously in some samples. These features are attributed to the effects of slow tectonic burial, which allows for thermal relaxation during compression. While nested, clockwise P–T–t loops provide a useful framework for Barrovian metamorphism, this study shows that the effects of slow burial can telescope this model in P–T space. Finally, the study demonstrates that eastern Tibet experienced a significant phase of crustal thickening during the Mesozoic, reinforcing the notion that the plateau may have a long history of uplift and growth. 相似文献
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吉林市伊舒盆地尚未进行过地热资源详查工作,本文在充分分析利用已有调查资料,总结前人地热勘查成功与失败经验的基础上,提出了地热资源的形成条件、分布规律、热储特征,圈定了现有经济技术条件下地热资源勘探开发有利地段,减少勘探开发风险。 相似文献
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Change detection with remotely sensed imagery plays an important role in land cover mapping, process analysis and dynamic information services. Euclidean distance, correlation and other mathematic metrics between spectral curves have been used to calculate change magnitude in most change detection methods. However, many pseudo changes would also be detected because of inter-class spectral variance, which remains a significant challenge for operational remote sensing applications. In general, different land cover types have their own spectral curves characterized by typical spectral values and shapes. These spectral values are widely used for designing change detection algorithms. However, the shape of spectral curves has not yet been fully considered. This paper proposes to use spectral gradient difference (SGD) to quantitatively describe the spectral shapes and the differences in shape between two spectra. Change magnitude calculated in the new spectral gradient space is used to detect the change/no-change areas. Then, a chain model is employed to represent the SGD pattern both qualitatively and quantitatively. Finally, the land cover change types are determined by pattern matching with the knowledgebase of reference SGD patterns. The effectiveness of this SGD-based change detection approach was verified by a simulation experiment and a case study of Landsat data. The results indicated that the SGD-based approach was superior to the traditional methods. 相似文献
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以北京地区地热流体中温度和矿物质含量较高的东坝凹陷南部地区作为实例,在完整的地热钻孔及相关地质资料基础上,通过对研究区断裂构造、热储层、热储盖层、地温场、流体水化学特性和富水性等地热地质条件进行分析,研究造成该区地热流体中温度、矿物质含量升高的主要原因。研究表明:受太阳宫断裂北段、良乡—前门断裂和楼梓庄断裂的切割作用,东坝凹陷南部地区热储层下落近千米,形成了一个较为封闭的“黑箱子”区域。这种独特的地质结构导致东坝凹陷南部地区接受东南城区地热田侧向补给较少,长期处于较为封闭的还原环境;太阳宫断裂北段存在深部的热源通道,地层深部的高温热流顺断裂上涌在东坝凹陷南部地区的热储层富集,因此该区地热流体表现出温度高、矿物质含量高、富水性差的特征,该研究对我国今后地热资源的开发具有积极的借鉴意义。 相似文献
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