The Geological Significance of the Deformation and Geochronology of the Xiaotian–Mozitan Shear Zone in the Dabie Orogenic Belt (East-Central China)

The Xiaotian–Mozitan Shear Zone(XMSZ) is the boundary of the Dabie High-grade Metamorphic Complex(DHMC) and the North Huaiyang Tectonic Belt. It was deformed in ductile conditions with a top-to-NW/WNW movement.Geothermometers applied to mineral parageneses in mylonites of the shear zone give a temperature range of 623–691°C for the predeformation and 515–568°C for the syndeformation, respectively, which indicates a retrograde process of evolution.A few groups of zircon U-Pb ages were obtained from undeformed granitic veins and different types of deformed rocks in the zone. Zircons from the felsic ultramylonites are all magmatic, producing a weighted mean 206 Pb/238 U age of 754 ± 8.1 Ma, which indicates the time of magmatic activities caused by rifting in the Neoproterozoic. Zircons from the granitic veins, cutting into the mylonites, are also of magmatic origin, producing a weighted mean 206 Pb/238 U age of 130 ± 2.5 Ma,which represents the time of regional magmatic activity in the Cretaceous. Zircons from the mylonitic gneisses are of anatectic-metamorphic origins and are characterized by a core-mantle interior texture, which yielded several populations of ages including the Neoproterozoic ages with a weighted mean 206 Pb/238 U age of 762 ± 18 Ma, similar to that of the felsic ultramylonites and the Early Cretaceous ages with a weighted mean 206 Pb/238 U age of 143 ± 1.8 Ma, indicating the anatectic metamorphism in the Dabie Orogenic Belt(DOB). Based on integrated analysis of the structure, thermal conditions of ductile deformation and the contact relations of the dated rocks, the activation time of the Xiaotian–Mozitan Shear Zone is constrained between ～143 Ma and 130 Ma, during which the DOB was undergoing a transition in tectonic regime from compression to extension. Therefore, the deformation and evolution of this shear zone plays an instrumental role in fully understanding this process. This research also inclines us to the interpretation of it as an extensional detachment, with regard to the tectonic properties of the shear zone. It may also be part of a continental scale extension in the background of the North China Block's cratonic destruction, dominated by the subduction and roll-back of the Paleo-Pacific plate, but more detailed work is needed in order to unravel its complicated development.     

基于元素含量和空间变异系数的化探异常信息识别

化探异常信息识别是化探数据分析最重要的任务之一, 也是化探数据在资源勘查领域受到广泛关注的最重要原因, 前人对化探异常信息识别做过大量研究, 这些研究中的大多数主要关注化探示踪元素的含量, 近而根据含量指标计算异常阈值, 而对示踪元素在空间中的分布特征关注较少。本文选择 1: 20万比例尺的克拉玛依幅为研究区, 根据区内金矿的矿床地球化学特征选择Ag、As、Au和Sb等4种元素为本区内金矿的示踪元素, 以地球化学元素分散晕形成理论为依据, 使用GIS技术和Matlab软件绘制研究区内4种金矿示踪元素的综合地球化学异常图。结果表明, 与传统阈值方法得到的化探异常图相比, 本文得到的化探异常图能够更好地指示研究区内已知金矿。     

黑潮延续体区域多源观测资料的海洋涡旋的统计对比分析

本文首次利用海面温度、海面高度异常和表面漂流浮标数据等多元观测资料定量比较了获取的涡旋特征要素。结果表明：虽然不同数据源得出的涡旋统计特征具有一定的差异,但具有相似的分布特征。在此基础上,还发现该研究区域存在异常涡旋（逆时针旋转的暖涡和顺时针旋转的冷涡）。     

我国海洋渔业互助保险发展研究——以舟山市远洋互保为例

海洋渔业是世界上多数沿海国家的一项既传统又古老的生产活动,但是由于海洋渔业的特点和风险的特殊性,造成海洋渔业保险工作很难开展。海洋渔业在我国国民经济中一直占据重要地位,海水产品产业占渔业总比重60%,但是因海洋渔业自身特点,海洋渔业保险的风险相较于一般渔业保险风险更大。改革开放至今,我国的海洋渔业商业保险从鼎盛期萎缩到部分商业保险公司已经退出当地渔业保险市场的程度。因此,就海洋渔业互助保险发展的实际情况来看,国家政策和政府补给应该是其中坚力量,构建符合我国国情的海洋渔业互助保险制度是有效化解现存矛盾的重要手段。文章通过结合具有代表性的我国舟山市远洋渔业互助保险实施中遇到的渔民群体对部分险种的有效了解不足、海洋渔业互助保险业务因保费补贴缺位的原因导致发展规模受限、巨灾风险分散机制缺失,政策扶持力度亟须加强等实际问题,提出我国政府在完善海洋渔业互助保险方面的优化建议即加强专业人才培养、加强我国政策支持的力度和实施政策性再保险。     

贵州红枫湖水面挥发性汞释放通量的测定

应用通量箱方法研究Hg在贵州红枫湖水表面挥发性汞的释放通量。当水温在20－24℃时,湖面汞的释放量在89－196mg/(h.m^2)之间,汞的释放通量白天达到最大值,而夜间降到最小,湖泊表面挥发性汞的释放通量均具有显著的昼夜变化规律,湖面汞的流通量与太阳辐射相关,与底泥中汞含量也明显相关。     

阿拉善盟“4·24”强沙尘暴天气过程分析

应用基本气象资料,对2010年4月24—25日阿拉善盟强沙尘暴天气过程进行了天气和动力诊断分析。结果表明:气旋后部有强冷暖空气交汇,造成水平温度梯度增大,从而加大了垂直切变偏差风。同时,强变压梯度和强斜压性形成了变压风,引起了不稳定能量的释放,从而引发地面大风,产生强沙尘暴。高空急流的活动会促使下沉运动,有利于地面气旋加强,造成低层辐合,高层辐散,非常有利于对流的发生与发展。     

新疆库鲁克塔格新元古代-早古生代裂陷槽深水沉积与沉积-构造古地理

根据库鲁克塔格、孔雀河露头区及其南盆内深部资料 ,尤其是多种类型的深水沉积的鉴别 ,得以建立区内地层及沉积相格架。分析表明 ,裂陷槽内南华系—奥陶纪地层属于同一构造环境的产物 ,沉积以深水陆棚 -槽盆相为主体 ,相带呈东西向展布 ,其空间分布范围比传统认识要广大得多。裂陷中心在孔雀河地区 ,南翼在盆内覆盖区北缘 ,原库鲁克塔格地区仅是其北翼 ;满加尔则是其南翼向南延的边缘坳陷 ,从而深化了其时空展布及构造演化历程。     

活动星系核红移分布中的准周期峰

本文作者在活动星系核红移分布（０＜ｚ≤０．２）中发现了准周期性的峰。这些峰分布于ｚ≈０．０３０，０．０６０，０．０９０，０．１２０处（其中ｚ＝０．０６０处的峰是１９６８年Ｂｕｒｂｉｄｇｅ发现的并于１９９０年证实）。红移数据的功率谱表明。这些峰值的准周期为△ｚ＝０．０２７±０．００２。两个相邻的峰所表征的空间距离为８１±６ｈ~（－１）Ｍｐｃ。这可能是宇宙大尺度结构中各个单元的特征尺度（Ｈ_０＝１００ｈ~（－１）Ｍｐｃ~（－１）ｍｓ~（－１）。     

中国小冰期的气候

在建立了近百年中国10个区的年平均气温序列的基础上,利用史料、冰芯δ18O及树木年轮,重建了各区近400～1000年的10年平均气温序列。分析表明,近千年来中国可能有5次冷期分别出现于1100’s～1150’s,1300’s～1390’s,1450’s～1510’s,1560’s～1690’s及1790’S～1890’S。第4次冷期主要在中国大陆中部最明显,而第5次冷期在中国南部较强。新疆、东北及闽台气温变化与中国其它部分特别是南部及西南有一定差异。如果把最后两次冷期作为中国小冰期的两次主要寒冷阶段,其30年平均气温可能比20世纪中期中国最暖的30年（1920’S～1940’S）低0．6～0．11℃。     

Late Cenozoic to recent transtensional deformation across the Southern part of the Gaoligong shear zone between the Indian plate and SE margin of the Tibetan plateau and its tectonic origin

Chuquicamata, in northern Chile, is one of the largest porphyry copper deposits in the world; the western side of its orebody is bounded by a major longitudinal fault, the West fault. We report paleomagnetic results from surface sites and drill cores from different geological units at Chuquicamata, especially within the late Eocene Fiesta granodiorite of the western block of the West fault. Characteristic remanent magnetizations (ChRM) were determined after detailed thermal or alternating field demagnetization. Soft components carried by multidomain magnetite crystals in the Fiesta granodiorite were removed by AF demagnetization at 10–20 mT. The ChRMs, not demagnetized by alternating fields up to 100 mT, have unblocking temperatures above 580 °C with ~ 75% of the magnetization removed in the temperature range of 580–590 °C. Optical and SEM mineralogical observations, and microprobe data indicate the occurrence of multidomain magnetite formed during a late magmatic stage of alteration coeval with strong oxidation of primary titanomagnetite and formation of ilmenite, hematite, pseudobrookite, and rutile. The characteristic directions have negative inclinations and declinations (330° to 230°); strongly deflected from the expected Eocene direction. Anisotropy of magnetic susceptibility (AMS), with degree up to 1.4, is carried by multidomain magnetite. AMS ellipsoids have subvertical foliations with azimuth varying strongly from N280° to N20°. We show that both the ChRMs and the AMS fabrics record the same apparent relative rotations between sites. Although the AMS anisotropy is high, there is no evidence for a solid-state deformation and the apparent rotation of the magnetic fabric is interpreted to be the consequence of small-block rotation. The apparent large (> 100°) counterclockwise rotations of small blocks within the Fiesta granodiorite suggest a wide damaged zone related to sinistral displacement along the West fault. This interpretation is consistent with previous models indicating that the Fiesta granodiorite was sinistrally translated and brought in front of the early Oligocene porphyry copper deposit during the Oligocene–early Miocene. This study shows that paleomagnetic markers are useful for improving the quantification and understanding of small-scale deformation within plutons adjacent to major fault zones.