Crust-Mantle Interaction in Dabie Orogenic Belt, Central China： Geochemical Evidence from Late Cretaceous Basalts

It has been suggested that eclogites in the Dabie orogenic belt are exhumation prod-ucts, which had subducted into the deep-seated mantle and undergone ultra-high pressure meta-morphism during the Triassic. But no direct evidence supports this process except the calculated p-T conditions from mineral thermobarometem. The Late Cretaceous basalts studied in the pres-ent paper, however, have provided some geochemical evidence for crust-mantle interaction in the area. These basalts are distributed in Mesozoic faulted basins in central and southern Dabieorogenic belt. Since little obvious contamination from continental crust and differentiation-crys-tallization were observed, it is suggested, based on a study of trace elements, that the basaltsare alkaline and resultant from batch partial melting of the regional mantle rocks, and share thesame or similar geochemical features with respect to their magma source. In the spider diagram normalized by the primitive mantle, trace element geochemistry data show that their mantle sources are enriched in certain elements concentrated in the continental crust, such as Pb, K,Rb and Ba, and slightly depleted in some HFSE such as Hf, P and Nb. Pb-Sr-Nd isotopic com-positions further suggest the mantle is the mixture of depleted mantle (DM) and enriched one(EMI EMII). This interaction can .explain the trace element characteristics of basaltic mag-mas, i.e.,the enrichment of Pb and the depletion of Hf, P and Nb in basalts can be interpre-ted by the blending of the eclogites in DOB (enriched in Pb and depleted in Hf, P and Nd)with the East China depleted mantle (As compared to the primitive mantle, it is neither en-riched in Pb nor depleted in Hf, P and Nb). It is also indicated that the eclogites in the Dahieorogenic belt were surely derived from the exhumation materials, which had delaminated into thedeep-seated mantle. Moreover, the process subsequently resulted in compositional variation of the mantle (especially in trace elements and isotopes) , as revealed by the late mantle-derivedbasalts in the Dabie orogenic belt.     

地震资料分频处理效果

在地震资料信噪比较低，常规处理效果不理想的情况下可考虑采用分频处理。首先根据频谱分析，确定频带范围，再按反射波在频带内的能量分布，确定分频频带。充分利用各个频带的反射能量，在每个频带内进行分频精细处理，提高分辩率，达到分辩较小断层的目的。     

贴近度在农业气象预报中的应用

近年来，模糊数学方法在国内农业气象中的应用日益广泛，已经应用的方法有模糊聚类、模糊综合评判、模糊相似分析、模糊决策等多种。模糊数学方法中的模型识别也是农业气象预报中最常用的一种预报方法。模型识别有模型识别的直接方法和间接方法两种。下面仅介绍模型识别的间接方法——贴近度的应用。     

建设"数字苏州"应该解决的关键问题

通过对“数字苏州”建设方案和最近几项信息化工程建设实践进行分析，提出了5个方面亟待解决的问题，并得出了基本结论。     

数字地震台电源管理的特点和维护要点

1 数字地震台供电模式的选择 由于数字地震台大多位于人烟稀少的偏僻地区,特别是山地.因此,这些台站具有以下共性:a) 温差大,易遭受雷击;b) 使用农电,交流电稳定性差,易出故障;c) 无人值守;d) 要求不间断供电.根据这些特点,要求数字地震台的供电系统具备下列功能:a) 输出电压应能满足不同设备的供电需求;b) 具备后备供电和管理能力;c) 要求供电系统能够适应农电较大的波动范围;d) 具备抑制浪涌和抑制瞬时过电压的能力;e) 具备完善的过电流、过热保护能力;f) 易维护.     

北秦岭丹凤地区早古生代花岗岩的Pb、Sr、Nd同位素地球化学特征

通过对北秦岭丹凤地区早古生代花岗岩的Ｐｈ、Ｓｒ、Ｎｄ同位素地球化学特征的系统研究，结合元素地球化学特征，证明早古生代具成分极性的枣园、黄柏岔、石门花岗岩是由于秦岭群斜长角闪岩和黑云斜长片麻岩部分熔融，近俯冲带以熔体与熔体的混合、远离俯冲带是前者产生的熔体与后者熔融后的残留相以不同比例混合形成的。     

重庆市专业气象服务的回顾

服务历来是气象工作的出发点和归宿。改革开放前,气象部门虽然开展了一些专业气象服务工作,但规模小,效益低。党的十一届三中全会后,尤其是近年专业气象服务获得迅速发展。现简要回顾一下重庆市专业气象服务的历程。西南气象处重庆预报台12月21日诞生的当天,就向长江航运管理局重庆分局调度室发出了重庆至宜昌的第一份航运天气预报,开创了我市专业气象服务的先例。在当时那样的设备和技术条件下,制发这样的专业天气预报,有何等艰辛是不言而喻的。随着重庆市国民经济的迅速恢复和发展,在气象为经     

北秦岭新元古代花岗岩类成因与构造环境的地球化学研究

花岗岩类地球化学特征和区域地质事件的综合分析结果表明,蔡凹岩体和黄柏峪岩体形成于活动陆缘或古岛孤环境,与古秦岭洋板块向北秦岭俯冲消减作用有关,属于Ⅰ型花岗岩,源岩来自于地幔派生物质;而德河岩体的形成可能是在板块俯冲作用早期,活动陆缘受板块俯冲作用的动力学影响,陆壳物质剪切改造所诱发岩浆的产物,属S型花岗岩,其源岩为陆壳碎屑物质。多种证据证明,北秦岭至少自新元古代就开始运行板块构造运动体制。     

西秦岭北带泥盆系研究的新进展

<正> 西秦岭北带主要指甘肃省西和一成县及其邻区。先后有葛利普(1931)、赵亚曾等(1931)、叶连俊等(1944)、黄振辉(1959)、王钰、俞昌民(1962)、兰州大学(1962)、李星学(1963)及西秦岭地质队(1964)均在该区进行过地层工作。1967—1970年陕西地质局区测队正式肯定“西汉水群”为西秦岭北带中泥盆世的代表沉积地层,并划分为雷家坝组与榆树坪组两个沉积旋迴及七个岩性段。1970年后,中国有色金属工业总公司甘肃地质勘查局研究所及有关单位在该区首次发现了上泥盆统地层的存在,并划分出了部份下泥盆统地层,推动了西秦岭北带泥盆纪地层研究工作的进展。