淹没丁坝群水力计算的试验研究

通过三姓浅滩定床物理模型试验,对淹没丁坝群的有关水力计算及对水位影响进行了试验研究,并提出了一种淹没丁坝群水面线计算的虚糙率方法.该方法简便实用,经实测资料验证,吻合较好.     

堤坝隐患探测技术研究进展

我国堤防数量众多,质量参差不齐,对人民生命财产安全造成了很大威胁。利用各种物理探测手段查找堤防隐患对保证防洪工程安全具有重要意义。本文简要总结了我国堤防隐患无损探测技术概况并对近年来在此领域内取得的主要进展进行了回顾与总结。文章最后对堤防无损探测技术今后的发展进行了展望。     

Process-based modeling of the overflow-induced growth of erosional channels

A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a non-cohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally.     

滇西高黎贡带～40Ma OIB型基性岩浆活动：消减特提斯洋片与印度板块断离的产物？

滇西高黎贡带基性岩脉形成于40～42Ma,以高 FeO、TiO_2,低 K_2O 含量为特征。虽然多数样品经历了不同程度的地壳混染,少量样品的 Nb/La 大于1,La/Yb 比值较小和 Mg~#值较高,显示了似洋岛玄武岩(OIB)的地球化学特征,从而为研究区提供了软流圈上涌的岩石学证据。模拟计算进一步暗示高黎贡基性岩脉的源区在尖晶石相橄榄岩中(<70km),说明软流圈地幔上涌到很浅的部位,这与目前青藏高原巨厚的岩石圈(>150km)形成鲜明对比。因此,～40Ma 高黎贡基性岩浆活动记录了研究区陆-陆碰撞后特殊的构造演化阶段。高黎贡带基性岩脉与达孜-甲马基性次火山岩在形成时间和地球化学性质上一致,两者均代表了碰撞后消减特提斯洋片与印度板块断离过程中软流圈上涌熔融的产物。     

东坑-菖蒲地区燕山晚期脉岩地球化学特征及其成因

本文以东坑-菖蒲地区发育的燕山晚期脉岩为对象,阐述了其岩石学和地球化学特征,并结合脉岩产出的大地构造背景,对其成因进行探讨。认为中基性脉岩为岩浆快速上升侵位所形成,其岩浆来源于地幔混染端员,源区受到富集地幔流体的交代作用;酸性脉岩具A2型花岗岩特征,岩浆源区较深,以地壳组分为主,受到富集地幔组分混染;推测该区部分铀成矿流体和成矿物质来源于地幔或下地壳。     

中国东南部中生代基性岩脉时空分布与形成机理

中国东南部发育的基性岩脉见于中生代各个时期,其年龄从内陆至沿海逐渐变新,与区内花岗岩年龄有相同的变化趋势,但两者活动高峰期不重合。基性岩脉主要发育于花岗岩体内部的拉裂带,鲜见穿过花岗岩上方或周围的沉积变质盖层。中生代各时期的基性岩脉与相应时期的中酸性和基性火山岩浆活动具有清晰的分带现象。进一步研究表明,基性岩脉与同期基性火山岩应是同源不同相的产物,而中酸性喷发的岩浆与基性喷发(侵入)的岩浆,则可能分别来自壳内熔融层和壳下(地幔)熔融层或壳内岩浆层的上部和下部。中酸性与基性岩浆活动的"错峰"现象和基性岩脉带的"迁移"现象,均与本区中生代陆壳系统的内能变化有关。     

华南富铀花岗岩和产铀花岗岩特征

文章简要叙述了我国南方5省(区)富铀花岗岩和产铀花岗岩概况,详细讨论了产铀花岗岩的主要特征:断裂构造发育,蚀变作用非常强烈,经常有二云母花岗岩出现,中基性和酸性脉岩比较发育。正是这些特征,决定了它们产出铀矿床的能力。     

Geochemistry of mafic dikes in the Singhbhum Orissa craton: implications for subduction-related metasomatism of the mantle beneath the eastern Indian craton

Mafic dikes, which transect the Mesoarchaean Singhbhum Granitoid Complex, are the most abundant members of the Newer Dolerite dikes of the Singhbhum Orissa craton. These dikes are subalkaline and exhibit a tholeiitic differentiation trend. Studied dikes underwent fractional crystallization of clinopyroxene and plagioclase. They show enriched patterns for the light rare earth elements (LREE) and large ion lithophile elements (LILE). On primitive mantle-normalized multi-element patterns, they possess Ba, Nb, Sr, P, and Ti depletions similar to subduction-related basaltic rocks. The high (La/Yb) _n and (Gd/Yb) _n ratios suggest that the studied mafic dikes were derived by low degrees of partial melting of a garnet-bearing source. Judging by trace elemental ratios (e.g. Ba/Y, Nb/Y, Ba/Th and Th/Nb), the studied dikes were derived from a mantle source metasomatized by a subduction component (e.g. fluids derived by dehydration of the subducting slab). We conclude that interaction between these fluids and the overlying mantle was the main cause of (LREE and LILE) enrichment and Nb (high field strength elements) depletion in the mafic dikes.     

Geochemical and Sr–Nd–Pb isotopic compositions of Mesozoic mafic dikes from the Gan-Hang tectonic belt,South China: petrogenesis and geodynamic significance

Mesozoic mafic dikes in the Gan-Hang tectonic belt (GHTB) provide an opportunity to explore both the nature of their mantle source(s) and the secular evolution of the underlying Mesozoic lithospheric mantle in the region. The geochronology and primary geochemical and Sr–Nd–Pb isotopic compositions of Group 1 (middle section of GHTB) and Group 2 (the rest of the section) dolerite dikes spanning the GHTB were investigated. K–Ar ages indicate that dikes of both groups were emplaced during the Cretaceous (131–69 Ma). The dikes are doleritic in composition and are enriched in both large ion lithophile elements (LILEs; e.g. Rb, Ba, and Pb) and light rare earth elements (LREEs), with a wide range of Eu anomalies, but are depleted in high field strength elements (HFSEs; e.g. Nb, Ta, and Ti) and heavy rare earth elements (HREEs). Dikes sampled in the middle section of the GHTB (Group 1) show more pronounced REE differentiation and a greater contribution from crustal material than those from the east and west sections (Group 2) and are similar to GHTB volcanic rocks in exhibiting a slight enrichment in LREEs. The dolerites are further characterized by a wide range in ⁸⁷Sr/⁸⁶Sr _i ?=?0.7041–0.7110, ¹⁴³Nd/¹⁴⁴Nd _i ?=?0.511951–0.512758, ?Nd _t ?=?–10.4 to?+5.6, and Pb isotopic ratios (²⁰⁶Pb/²⁰⁴Pb _i ?=?18.1–18.3, ²⁰⁷Pb/²⁰⁴Pb _i ≈ 15.6, and ²⁰⁸Pb/²⁰⁴Pb _i ?=?38.2–38.7). The dikes have undergone fractional crystallization of olivine, clinopyroxene, plagioclase, and Ti-bearing phases, except for dikes from the Anding area, which possibly experienced fractionation of plagioclase. Geochemically, all the dike samples originated from mantle sources ranging in composition from depleted to enriched that contained a component of foundered lower crust; crustal contamination during the ascent of these magmas was negligible. In the context of the late Mesozoic lithospheric extension across South China, mafic dike magmatism was likely triggered by the reactivation of deep faults, which promoted foundering of the lower crust and subsequent mantle upwelling in the GHTB.     

基性岩脉与金成矿的关系

基性岩脉是大陆伸展背景下,主要来自陆下软流圈或地幔岩石圈的岩浆侵入岩体.大量研究成果表明基性岩脉发育与金矿脉在空间展布、构造格局和形成时间具有紧密依存关系,虽然对基性岩脉是否为金矿脉提供金源尚无统一定论,但是根据基性岩脉与金矿化紧密的时空关系,基性岩脉可以作为找金矿的良好标志.