重庆北碚长兴期腕足动物群落的划分及其地层意义

重庆北碚地区晚二叠世长兴期地层出露良好,剖面位于北碚代家沟东北部,经过详细调查研究,在厚度为110.5m的长兴组石灰岩地层中发现有丰富的腕足动物,共有28属46种。按照识别与划分化石群落的5个基本条件,本区长兴期腕足动物可以划分为3个化石群落,本区长兴期生态地层建立3个化石群落带,自上而下为:Uncinunellina-Peltichia带、Haydenella-Perigeyerella带、Oldhamina-Meekella带。从而将本区长兴期地层三分。     

利津洼陷沙四上亚段滩坝沉积特征及控制因素分析

通过岩心观察、测井和地震资料分析,运用沉积学、层序地层学理论,将利津洼陷沙四上亚段分为1个层序3个体系域（LST、TST、HST）,并细分为7个准层序组。研究了滩坝砂岩的沉积特征和在准层序组内的平面展布,以准层序组1、2滨浅湖滩坝最发育,准层序组3、4风暴滩坝最发育,准层序组6、7砂质滩坝发育差但发育碳酸盐滩坝。对滩坝控制因素进行了探讨,首次提出了“气（气候）-源（物源）-盆（盆地）”系统控滩坝的分析思路,是对传统“源控论”的完善与补充,可更合理解释滩坝的成因和分布,增加预测性。     

Prograde garnet growth along complex <Emphasis Type="Italic">P–T–t</Emphasis> paths: results from numerical experiments on polyphase garnet from the Wölz Complex (Austroalpine basement)

Garnet in metapelites from the Wölz Complex of the Austroalpine crystalline basement east of the Tauern Window characteristically consists of two growth phases, which preserve a comprehensive record of the geothermal history during polymetamorphism. From numerical modelling of garnet formation, detailed information on the pressure–temperature–time (P–T–t) evolution during prograde metamorphism is obtained. In that respect, the combined influences of chemical fractionation associated with garnet growth, modification of the original growth zoning through intragranular diffusion and the nucleation history on the chemical zoning of garnet as P and T change during growth are considered. The concentric chemical zoning observed in garnet and the homogenous rock matrix, which is devoid of chemical segregation, render the simulation of garnet growth through successive equilibrium states reliable. Whereas the first growth phase of garnet was formed at isobaric conditions of ～3.8 kbar at low heating/cooling rates, the second growth phase grew along a Barrovian P–T path marked with a thermal peak of ～625°C at ～10 kbar and a maximum in P of ～10.4 kbar at ～610°C. For the heating rate during the growth of the second phase of garnet, average rates faster than 50°C Ma^?1 are obtained. From geochronological investigations the first growth phase of garnet from the Wölz Complex pertains to the Permian metamorphic event. The second growth phase grew in the course of Eo-Alpine metamorphism during the Cretaceous.     

Petrogenesis of Permian alkaline lamprophyres and diabases from the Spanish Central System and their geodynamic context within western Europe

Basic to ultrabasic alkaline lamprophyres and diabases intruded within the Spanish Central System (SCS) during Upper Permian. Their high LREE, LILE and HFSE contents, together with positive Nb–Ta anomalies, link their origin with the infiltration of sublithospheric K-rich fluids. These alkaline dykes may be classified in two distinct groups according to the Sr–Nd isotope ratios: (1) a depleted PREMA-like asthenospheric component, and (2) a BSE-like lithospheric component. A slight enrichment in radiogenic ²⁰⁷Pb and ²⁰⁸Pb allows the contribution of a recycled crustal or lithospheric component in the mantle sources. The intrusion of this alkaline magmatism is likely to have occurred due to adiabatic decompression and mantle upwelling in the context of the widespread rifting developed from Carboniferous to Permian in western Europe. The clear differences in the geochemical affinity of Lower Permian basic magmas from north-western and south-western Europe might be interpreted in terms of a more extensive separation of both regions during that period, until they were assembled during Upper Permian. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cenomanian-lower coniacian radiolarian assemblages from the Naiba reference section (Sakhalin)

Reexamination of radiolarians from the Naiba and Bykovo formations of the Naiba reference section (West Sakhalin Mountains) is carried out. Distinguished in the section are the Cromyomma (?) nodosa-Amphipyndax sp. A (terminal early Cenomanian), Cuboctostylus kasinzovae-C. sakhalinensis (Middle Cenomanian), Cuboctostylus trifurcatus-Cassideus yoloensis (terminal middle-late Cenomanian), and Spongodiscus concentricus-Multastrum robustum (late Turonian to early Coniacian probably) assemblages. According to results of comparative analysis for North Pacific regions, concurrent radiolarian assemblages from the Naiba section and California contain up to 40% of species in common, whereas taxonomic similarity with assemblages from Japan is insignifican in contrast.     

Using chemical and microbiological indicators to track the impacts from the land application of treated municipal wastewater and other sources on groundwater quality in a karstic springs basin

Multiple chemical constituents (nutrients; N, O, H, C stable isotopes; 64 organic wastewater compounds, 16 pharmaceutical compounds) and microbiological indicators were used to assess the impact on groundwater quality from the land application of approximately 9.5 million liters per day of treated municipal sewage effluent to a sprayfield in the 960-km² Ichetucknee Springs basin, northern Florida. Enriched stable isotope signatures (δ¹⁸O and δ²H) were found in water from the effluent reservoir and a sprayfield monitoring well (MW-7) due to evaporation; however, groundwater samples downgradient from the sprayfield have δ¹⁸O and δ²H concentrations that represented recharge of meteoric water. Boron and chloride concentrations also were elevated in water from the sprayfield effluent reservoir and MW-7, but concentrations in groundwater decreased substantially with distance downgradient to background levels in the springs (about 12 km) and indicated at least a tenfold dilution factor. Nitrate-nitrogen isotope (δ¹⁵N–NO₃) values above 10 ‰ in most water samples were indicative of organic nitrogen sources except Blue Hole Spring (δ¹⁵N–NO₃ = 4.6–4.9 ‰), which indicated an inorganic source of nitrogen (fertilizers). The detection of low concentrations the insect repellent N,N-diethyl-metatoluamide (DEET), and other organic compounds associated with domestic wastewater in Devil’s Eye Spring indicated that leakage from a nearby septic tank drainfield likely has occurred. Elevated levels of fecal coliforms and enterococci were found in Blue Hole Spring during higher flow conditions, which likely resulted from hydraulic connections to upgradient sinkholes and are consistent with previoius dye-trace studies. Enteroviruses were not detected in the sprayfield effluent reservoir, but were found in low concentrations in water samples from a downgradient well and Blue Hole Spring during high-flow conditions indicating a human wastewater source. The Upper Floridan aquifer in the Ichetucknee Springs basin is highly vulnerable to contamination from multiple anthropogenic sources throughout the springs basin.     

Petrogenesis of greenstones from the Mino–Tamba belt, SW Japan: Evidence for an accreted Permian oceanic plateau

Permian greenstones in the Jurassic Mino–Tamba accretionary complex, southwest Japan, are divided into three distinct series on the basis of their geological occurrence, mineralogy, and geochemistry. A low-Ti series (LTS) is associated with Lower Permian chert and limestone, and is the most voluminous of the three series. The LTS shows slightly more enriched geochemical and isotopic characteristics than MORB. A transition series (TS) is mainly associated with Lower Permian chert, and has more enriched geochemical signatures than MORB. Its isotopic characteristics are divided into enriched and depleted types. A high-Ti series (HTS) occurs as sills and hyaloclastites within Middle Permian chert and as dikes intruding the TS. Some HTS rocks have high MgO contents. The HTS is characterized by enrichment in incompatible trace elements and an isotopic composition comparable to HIMU-type basalt. The geochemistry of the voluminous LTS is similar to that of the oceanic basalt series of the Kerguelen plateau, suggesting production by partial melting of a shallow mantle plume head below thick oceanic lithosphere in Early Permian time. We infer that the TS formed simultaneously at the margins of the mantle plume head. In contrast, the HTS may have resulted from partial melting of a deep mantle plume tail in Middle Permian time. Permian greenstones in the Mino–Tamba belt may have thus formed by superplume activity in an intra-oceanic setting. Given the presence of two known contemporary continental flood basalt provinces (Siberia and Emeishan) and some accreted oceanic plateau basalts, the vast magmatism of the Mino–Tamba oceanic plateau suggests a large-scale superplume pulse in Permian time. Accretion of oceanic plateaux may have played an important role in the growth of continental margins and island arcs in Japan and elsewhere in the circum-Pacific region.     

Two magma series and associated ore deposit types in the Permian Emeishan large igneous province, SW China

The Late Middle Permian ( 260 Ma) Emeishan large igneous province in SW China contains two magmatic series, one comprising high-Ti basalts and Fe-rich gabbroic and syenitic intrusions, the other low-Ti basalts and mafic–ultramafic intrusions. The Fe-rich gabbros are spatially and temporally associated with syenites. Each series is associated with a distinctive type of mineralization, the first with giant Fe–Ti–V oxide ore deposits such as Panzhihua and Baima, the second with Ni–Cu–(PGE) sulfide deposits such as Jinbaoshan, Limahe and Zhubu. New SHRIMP zircon U–Pb isotopic data yielded 263 ± 3 Ma for the Limahe intrusion, 261 ± 2 Ma for the Zhubu intrusion and 262 ± 2 Ma for a syenitic intrusion. These new age dates, together with previously reported SHRIMP zircon U–Pb ages, suggest that all these intrusions are contemporaneous with the Emeishan flood basalts and formed during a major igneous event at ca. 260 Ma.The oxide-bearing intrusions have higher Al₂O₃, FeO (as total iron) and total alkalis (Na₂O + K₂O) but lower MgO than the sulfide-bearing intrusions. All intrusions are variably enriched in LREE relative to HREE. The oxide-bearing intrusions display positive Nb- and Ti-anomalies and in certain cases negative Zr–Hf anomalies, whereas the sulfide-bearing intrusions have obvious negative Nb- and Ti-anomalies, a feature of crustal contamination. Individual intrusions have relatively small ranges of Nd(t) values. All the intrusions, however, have Nd(t) values ranging from − 3.9 to + 4.6, and initial ⁸⁷Sr/⁸⁶Sr ratios from 0.7039 to 0.7105. The syenites have very low MgO (< 2 wt.%) but highly variable Fe₂O₃ (2.5 to 13 wt.%) with initial ⁸⁷Sr/⁸⁶Sr ratios ranging from 0.7039 to 0.7089. Magmas from both series could have derived by melting of a heterogeneous mantle plume: the high-Ti series from a Fe-rich, more fertile source and the low-Ti series from a Fe-poor, more refractory source. In addition, the low-Ti series underwent significant crustal contamination. The two magma series evolved along different paths that led to distinct mineralization styles.     

用接收函数方法研究中国及邻区上地幔间断面的埋藏深度

使用中国及邻区的18个数字化地震台的宽频带三分向远震记录图,筛选计算得到了263条径向接收函数,并拾取了在41Okm和660km间断面上的透射转换震相P4S、P660S与P波的到时差.通过调整各台站之下的速度模型中这两个间断面的深度,使理论接收函数的P4S、P660S与P波的到时差与观测值相符,最终确定这两个间断面的实际埋藏深度.结果表明,各台站之下4km间断面的平均深度为403km,具有明显的横向不均匀性和区域性,其中北京台、西安台、兰州台和恩施台等的埋藏深度较浅,琼中台、CHTO等台较深.660km间断面的平均埋藏深度为663km,也存在明显的横向不均匀性,其中牡丹江台和MAJO台的较深,琼中台和HYB台的较浅.