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91.
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地表温度被认为是影响生态系统的关键因子之一,它与许多地表过程有关。目前,热红外卫星遥感技术是获取有关区域和全球尺度地表温度信息的一个有效、可行的手段。针对不同卫星上搭载的热红外传感器,许多学者开展了大量的研究,其中针对单波段热红外的特点(如Landsat TM/ETM+,CBERS和HJ-1B)提出了单通道(或单窗)算法。该类算法需要准确的地表比辐射率和大气参数(如大气水分含量)。这些参数在现实中又很难轻易获得,从而在一定程度上限制了现有算法的应用。针对HJ-1B高回访频率的特点,本文提出了利用多时相影像的时空信息来直接反演地表温度的Multi-Temporal and Spatial Information-Based Single Channel(MTSC),以解决现有算法对地表比辐射率和大气参数的过度依赖性。实例分析结果显示,基于MTSC法由HJ-1B反演得到的地表温度结果与MODIS地表(陆表和海表)温度产品具有很好的空间一致性;HJ-1B的陆表温度结果总体上被高估了约1 K,而海表温度结果总体上被高估了0.5 K;同时,MTSC法得到的HJ-1B地表温度结果具有更好的细节和空间完整性。最后,通过分析和讨论指出了一些可能的完善途径,如相似像元的确定、修改优化求解中的目标函数、参数的自适应初始化等,以便提高MTSC法的反演精度和实用性。 相似文献
93.
为了深入研究硬岩型铀矿化(点、带)的地球物理特征,在桃山、红山子地区开展了综合物探测量.结果表明,在△T磁异常平面等值线图中,铀矿床(点、带)一般位于强弱磁异常过渡地带偏弱磁异常一侧,电阻率断面图中多位于高低阻梯度变化带或中低阻区,电阻率平面图中多位于中低阻过渡带偏低阻一侧.该硬岩型铀矿化地球物理特征为寻找该类铀矿有利地段提供了重要信息. 相似文献
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Post-collisional, K-rich mafic magmatism in south Tibet: constraints on Indian slab-to-wedge transport processes and plateau uplift 总被引:8,自引:0,他引:8
Zhengfu Guo Marjorie Wilson Maoliang Zhang Zhihui Cheng Lihong Zhang 《Contributions to Mineralogy and Petrology》2013,165(6):1311-1340
Post-collisional (23–8 Ma), potassium-rich (including ultrapotassic and potassic) mafic magmatic rocks occur within the north–south-trending Xuruco lake–Dangre Yongcuo lake (XDY) rift in the Lhasa terrane of the southern Tibetan Plateau, forming an approximately 130-km-long semi-continuous magmatic belt. They include both extrusive and intrusive facies. Major and trace element and Sr–Nd–Pb isotopic data are presented for all of the known exposures within the XDY rift. The potassium-rich, mafic igneous rocks are characterized by high MgO (5.9–10.8 wt.%), K2O (4.81–10.68 wt.%), Ba (1,782–5,618 ppm) and Th (81.3–327.4 ppm) contents, and relatively high SiO2 (52.76–58.32 wt.%) and Al2O3 (11.10–13.67 wt.%). Initial Sr isotopic compositions are extremely radiogenic (0.712600–0.736157), combined with low (206Pb/204Pb) i (18.28–18.96) and (143Nd/144Nd) i (0.511781–0.512046). Chondrite-normalized rare earth element patterns display relatively weak negative Eu anomalies. Primitive mantle-normalized incompatible trace element patterns exhibit strong enrichments in large ion lithophile elements relative to high-field-strength elements and display strongly negative Ta–Nb–Ti anomalies. The combined major and trace element and Sr–Nd–Pb isotopic characteristics of the K-rich igneous rocks suggest that the primitive magmas were produced by 1–10 % partial melting of an asthenospheric mantle source enriched by both fluids and partial melts derived from Indian passive continental margin sediments subducted into the shallow mantle as a consequence of the northward underthrusting of the Indian continental lithosphere beneath Tibet since the India–Asia collision at ~55 Ma. The best-fit model results indicate that a melt with trace element characteristics similar to those of the K-rich rocks could be generated by 8–10 % partial melting of a metasomatized mantle source in the south and 1–2 % melting in the north of the XDY rift. Trace element and Sr–Nd–Pb isotopic modeling indicate that the proportion of fluid derived from the subducted sediments, for which we use as a proxy the Higher Himalayan Crystalline Sequence (HHCS), in the mantle source region increases from north (rear-arc) to south (front-arc), ranging from 0 to 5 %, respectively. Correspondingly, the proportion of the melt derived from the subducted HHCS in the source increases from north (2 %) to south (15 %). The increasing proportion of the fluid and melt component in the mantle source from north to south, together with a southward decreasing trend in the age of the K-rich magmatism within the XDY rift, is inferred to reflect rollback of the subducted Indian lithospheric mantle slab during the period 25–8 Ma. Slab rollback may be linked to a decreasing convergence rate between India and Asia. As a consequence of slab rollback at 25 Ma beneath the Lhasa terrane, its geodynamic setting was transformed from a convergent (55–25 Ma) to an extensional (25–8 Ma) regime. The occurrence of K-rich magmatism during the period 25–8 Ma is a consequence of the decompression melting of an enriched mantle source, which may signal the onset of extension in the southern Tibetan Plateau and provide a petrological record of the extension process. 相似文献
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滩间山金矿区斜长花岗斑岩出露于柴达木盆地北缘构造带,是区内出露较大的斑岩体。利用LA-MC-ICPMS锆石定年方法,测得斜长花岗斑岩锆石的年龄为2 416~336Ma,可分为3组:2 416~2 365,1 797~1 602,358~336Ma。对锆石矿物成因研究表明,第一组和第二组年龄为继承性锆石的年龄,反映其源岩有前寒武纪变质岩或同期岩浆岩的物质;第三组为斜长花岗斑岩的结晶年龄,表明岩体形成于早石炭世,为华力西中期斜长花岗斑岩。岩石地球化学特征表明,岩石属钙碱性系列偏铝质岩石,为I型花岗岩,形成于后碰撞环境。结合锆石的年龄测定数据,认为斜长花岗斑岩物质具有多来源的特点,华力西中期是本区金矿形成的一个重要成矿期。 相似文献
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100.
A grain-size record from Beijing region in Northern China: Late Quaternary paleoclimate oscillation in response to global change 总被引:1,自引:0,他引:1
Guifang Yang Zhiliang Ge Qing Dai Jie Cheng Gongming Yin Lihong Zan Jingwei Liu 《Frontiers of Earth Science》2009,3(2):164-170
Numerous samples taken from one core at the Beijing plain were utilized to characterize the paleoclimatic configuration of
the study area and its possible relation to global control since the last interglaciation. We presented here a detailed grain-size
record for the full length of Late Pleistocene, along with the optical simulated luminescence (OSL) dating. Our findings revealed
that Late Pleistocene of the study area started approximately at 110 ka B.P. represented by the thick sediments of 31 m in
Changping depression. Four sedimentary cycles were outlined in the core during Late Pleistocene, corresponding to marine isotope
stage (MIS) 5 to 2. Controlled by regional geology and global climatic setting, eight paleoclimatic periods were identified
simultaneously in the study area on the time scale of 104 year, with the warm and moist climate being found at 110 — 96, 92 — 76, 67 — 56, and 28 — 18 ka B.P.. The climatic instabilities
on a millennial scale in Late Pleistocene were characterized largely by the occurrence of 6 strong Heinrich events shown by
comparatively coarse groups. These variations correlate well with those documented in the GRIP Greenland and in the Northern
Atlantic Ocean, though more complex features may exist on the long time scale. 相似文献