Taxonomy and stratigraphy of late Barremian–Albian species of Horiopleura Douvillé (Hippuritida,Polyconitidae) of the Mediterranean and southwestern Asian regions

The genus Horiopleura Douvillé is restricted to the Mediterranean and southwestern Asian regions, and is represented by eight species developed during the late Barremian–Albian. This revision of species contributed to delineate generic and specific characters. The definition of species is based on a set of external and internal qualitative and quantitative characters, the key characters being size, radial bands, ornamentation and the presence of a left posterior canal. Morphometry documents the dimorphism of some species, corroborated by regression analysis. Horiopleura dumortieri is an upper Barremian–lowermost Bedoulian species from SE France, Horiopleura brevis n. sp. is a Bedoulian, Mediterranean species, extending to the lower Gargasian, Horiopleura gigantea (pro Monopleura) is a Bedoulian species, restricted the Ukrainian Carpathes. Horiopleura lamberti and H. almerae are Upper Aptian to lower Albian species, and are known from Southern Europe and North Africa. Horiopleura haydeni is essentially late Aptian and typifies the southwestern Asia “Yasin fauna”. Horiopleura distefanoi and H. gemmellaroi (both formerly placed in Polyconites) are restricted to the Albian of the peri-Adriatic regions and North Africa, the former being present in the Middle East. Multiple correspondence analysis using six categorical variables and their categorical states, applied to the comparison of species, tends to corroborate our overall taxonomic frame-work, and reveals three groups of species with distinctive ages.     

Yandong porphyry Cu deposit,Xinjiang, China—Geology,geochemistry and SIMS U–Pb zircon geochronology of host porphyries and associated alteration and mineralization

The Yandong porphyry copper deposit, located in the Eastern Tianshan Mountains, Xinjiang, China, is part of the Central Asian Orogenic Belt. The Yandong deposit is hosted by a volcanic complex in the Early Carboniferous Qi’eshan Group and a felsic intrusion. The complex consists of andesite, basalt, diorite porphyry, and porphyritic quartz diorite. The felsic intrusion is a plagiogranite porphyry emplaced within the complex. The diorite porphyry and plagiogranite porphyry yield SIMS zircon U–Pb ages of 340.0 ± 3 and 332.2 ± 2.3 Ma, respectively. Element geochemistry shows that both the complex and plagiogranite porphyry formed in the Dananhu–Tousuquan island arc, a Carboniferous magmatic arc.The diorite porphyry and plagiogranite porphyry are host porphyries, but the plagiogranite porphyry is a productive porphyry. It caused the porphyry-style Cu mineralization and associated alteration. The alteration assemblages include early potassic and propylitic assemblages. These were overprinted by a chlorite–sericite assemblage, which in turn was overprinted by a late phyllic assemblage. The phyllic alteration is associated with the highest Cu grades. The mineralization is recognized to include three stages, from early to late: stage 1, a potassic alteration associated with a chalcopyrite + pyrite assemblage; stage 2, represented by chlorite–sericite alteration with a chalcopyrite + pyrite assemblage; and stage 3, the main-ore stage that is marked by phyllic alteration with chalcopyrite + pyrite ± molybdenite and producing more than 70% of the total copper production at Yandong. Yandong may represent a common scenario for Paleozoic porphyry Cu systems in the Central Asian Orogenic Belt.     

外束离子感生发光法及其应用研究初探

基于外束质子激发Ｘ荧光分析（ＰｒｏｔｏｎＩｎｄｕｃｅｄＸｒａｙＥｍｉｓｓｉｏｎ———ＰＩＸＥ法）的外束离子感生发光（ＩｏｎＢｅａｍＩｎｄｕｃｅｄＬｕｍｉｎｅｓｃｅｎｃｅ，ＩＢＩＬ）实验装置，实现了ＩＢＩＬ对地质样品斜长石（钙长石）中元素铁的化学价态的直接分析。实验结果表明，Ｆｅ２＋和Ｆｅ３＋光谱峰分别位于５５３ｎｍ和６８２ｎｍ清晰分离，Ｆｅ３＋光谱峰清晰突出，Ｆｅ２＋峰也可确认     

Analysis of karst hydrodynamics through comparison of dissolved and suspended solids' transport

In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of $T\text{–}C$ curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005).     

Formation process of mid-Neoproterozoic mafic rocks from the western Jiangnan Orogen,South China: insights from SHRIMP U–Pb dating and geochemical analysis

The mid-Neoproterozoic tectonic setting of the Jiangnan Orogen (JO) is uncertain due to the ongoing debate regarding the history of interactions between the Yangtze and Cathaysia Blocks. Extensive magmatic rocks with ages >830 Ma are observed in the eastern JO and are reported to indicate their formation conditions; however, such magmatic rocks are rare in the western JO. This paper presents data from samples collected from two ultramafic intrusions in northern Guangxi province that yield SHRIMP U–Pb ages of 848 ± 7 and 836 ± 5 Ma. These two intrusions have similar geochemical compositions; are enriched in LILE (Rb, Ba, Th, and Pb) relative to HFSE (Hf, Zr, Nb, Ta, and Y), reflecting an arc-like signature; and are derived from the same source. The intrusions have positive εNd(t) and εHf(t) values, implying a depleted mantle source. Comparing the Neoproterozoic mafic–ultramafic rocks of the JO, differences exist between the rocks that formed at 860–830, 830–800, and 800–740 Ma in terms of their mantle sources and formation conditions. Considering the geochemical composition and ages of formation of the strata and the deep structure of the western JO, we speculate that the western JO was a back-arc foreland basin, which experienced shallow subduction-related and arc-like magmatism during the period between 860 and 830 million years. In contrast to the western JO, the eastern JO may have been a back-arc basin with oceanic crustal basement during that time. The JO formed between 830 and 800 million years in association with subduction-related collisional magmatism due to the amalgamation of the Yangtze and Cathaysia Blocks. Subsequently, magmatism occurred in the JO that resulted from the post-orogenic extension.     

Laser-ICP-MS U–Pb zircon ages and geochemical and Sr–Nd–Pb isotopic compositions of the Niyasar plutonic complex,Iran: constraints on petrogenesis and tectonic evolution

We conducted geochemical and isotopic studies on the Oligocene–Miocene Niyasar plutonic suite in the central Urumieh–Dokhtar magmatic belt, in order better to understand the magma sources and tectonic implications. The Niyasar plutonic suite comprises early Eocene microdiorite, early Oligocene dioritic sills, and middle Miocene tonalite + quartzdiorite and minor diorite assemblages. All samples show a medium-K calc-alkaline, metaluminous affinity and have similar geochemical features, including strong enrichment of large-ion lithophile elements (LILEs, e.g. Rb, Ba, Sr), enrichment of light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs, e.g. Nb, Ta, Ti, P). The chondrite-normalized rare earth element (REE) patterns of microdiorite and dioritic sills are slightly fractionated [(La/Yb)_n = 1.1–4] and display weak Eu anomalies (Eu/Eu* = 0.72–1.1). Isotopic data for these mafic mantle-derived rocks display I_Sr = 0.70604–0.70813, ?_Nd (microdiorite: 50 Ma and dioritic sills: 35 Ma, respectively) = +1.6 and ?0.4, TDM = 1.3 Ga, and lead isotopic ratios are (²⁰⁶Pb/²⁰⁴Pb) = 18.62–18.57, (²⁰⁷Pb/²⁰⁴Pb) = 15.61–15.66, and (²⁰⁸Pb/²⁰⁴Pb) = 38.65–38.69. The middle Miocene granitoids (18 Ma) are also characterized by relatively high REE and minor Eu anomalies (Eu/Eu* = 0.77–0.98) and have uniform initial ⁸⁷Sr/⁸⁶Sr (0.7065–0.7082), a range of initial Nd isotopic ratios [?Nd(T)] varying from ?2.3 to ?3.7, and Pb isotopic composition (²⁰⁶Pb/²⁰⁴Pb) = 18.67–18.94, (²⁰⁷Pb/²⁰⁴Pb) = 15.63–15.71, and (²⁰⁸Pb/²⁰⁴Pb) = 38.73–39.01. Geochemical and isotopic evidence for these Eocene–Ologocene mafic rocks suggests that the magmas originated from lithospheric mantle with a large involvement of EMII component during subduction of the Neotethyan ocean slab beneath the Central Iranian plate, and were significantly affected by crustal contamination. Geochemical and isotopic data of the middle Miocene granitoids rule out a purely crustal-derived magma genesis, and suggest a mixed mantle–crustal [MASH (melting, assimilation, storage, and homogenization)] origin in a post-collision extensional setting. Sr–Nd isotope modelling shows that the generation of these magmas involved ～60% to 70% of a lower crustal-derived melt and ～30% to 40% of subcontinental lithospheric mantle. All Niyasar plutons exhibit transitional geochemical features, indicating that involvement of an EMII component in the subcontinental mantle and also continental crust beneath the Urumieh–Dokhtar magmatic belt increased from early Eocene to middle Miocene time.     

Mineralogy,geochemistry, and geotectonic significance of the Neoproterozoic ophiolite of Wadi Arais area,south Eastern Desert,Egypt

ABSTRACT

The dismembered ophiolites in Wadi Arais area of the south Eastern Desert of Egypt are one of a series of Neoproterozoic ophiolites found within the Arabian–Nubian Shield (ANS). We present new major, trace, and rare earth element analyses and mineral composition data from samples of the Wadi Arais ophiolitic rocks with the goal of constraining their geotectonic setting. The suite includes serpentinized ultramafics (mantle section) and greenschist facies metagabbros (crustal section). The major and trace element characteristics of the metagabbro unit show a tholeiitic to calc-alkaline affinity. The serpentinized ultramafics display a bastite, or less commonly mesh, texture of serpentine minerals reflecting harzburgite and dunite protoliths, and unaltered relics of olivine, orthopyroxene, clinopyroxene, and chrome spinel can be found. Bulk-rock chemistry confirms harzburgite as the main protolith. The high Mg# (91.93–93.15) and low Al₂O₃/SiO₂ ratios (0.01–0.02) of the serpentinized peridotite, together with the high Cr# (>0.6) of their Cr-spinels and the high NiO contents (0.39–0.49 wt.%) of their olivines, are consistent with residual mantle rocks that experienced high degrees of partial melt extraction. The high Cr# and low TiO₂ contents (0.02–0.34 wt.%) of the Cr-spinels are most consistent with modern highly refractory fore-arc peridtotites and suggest that these rocks probably developed in a supra-subduction zone environment.     

线性分布基床系数弹性地基梁有限单元法改进

弹性地基梁法常用于研究土和结构的相互作用,对于均布荷载和边界条件简单的弹地基梁,采用理论解即可方便地进行计算。侧向荷载作用下桩体、嵌入式挡墙一般根据弹性地基梁理论进行分析,并假定基床系数随深度增加。对于基床系数呈线性分布或呈均匀分布但边界条件复杂的弹性地基梁理论求解困难,通常采用有限差分法或有限单元法近似求解。采用有限单元法计算线性分布基床系数弹性地基梁时,若单元划分数量不够,就存在计算精度不足的问题。采用加权余量法推导了更为精确的2节点5次位移函数和相应的单刚矩阵,得出了线性分布荷载作用下挠度的5次多项式近似解,从而实现只需划分很少的单元数,节点位移及单元内位移的分布即可达到较高的计算精度,极大地提高了计算效率,单元内力的分布可直接由位移函数导出,简化了后处理计算程序。     

Lithium elemental and isotopic variations in rock-melt interaction

Despite the occurrence of highly variable lithium (Li) elemental distribution and isotopic fractionation in mantle mineral, the mechanism of Li heterogeneity and fractionation remains a controversial issue. We measured Li contents and isotopic compositions of olivine and clinopyroxene xenocrysts and phenocrysts from kamafugite host lavas, as well as minerals in melt pockets occurring as metasomatic products in peridotite xenoliths from the Western Qinling, central China. The olivine xenocrysts in the kamafugites show compositional zonation. The cores have high Mg# (100 × Mg/(Mg+Fe); 91.0–92.2) and Li abundances (5.63–21.7 ppm), low CaO contents (≤0.12 wt%) and low δ⁷Li values (−39.6 to −6.76‰), which overlap with the compositional ranges of the olivines in the melt pockets as well as those in peridotite xenoliths. The rims of the olivine xenocrysts display relatively low Mg# (85.9–88.2), high CaO contents (0.19–0.38 wt%) and high δ⁷Li values (18.3–26.9‰), which are comparable to the olivine phenocrysts (Mg#: 86.4–87.1; CaO: 0.20–0.28 wt%; Li: 12.4–36.8 ppm; δ⁷Li: 18.1–26.0‰) and the silicate-melt metasomatized olivines. The clinopyroxene phenocrysts and clinopyroxenes in the melt pockets have no distinct characteristics with respect to the Li abundances and δ⁷Li values, but show higher and lower CaO contents, respectively, than the clinopyroxenes from silicate and carbonatite metasomatized samples. These features indicate that Li concentration and isotopic signatures of the cores of the xenocrysts recorded carbonatite melt-peridotite reaction (carbonatite metasomatism) at mantle depth, and the variations in the rims probably resulted from xenocryst–host magma interaction during ascent. Our results reveal that the interaction with carbonatite and silicate melts gave rise to an increase in Li abundance in minerals of peridotite xenoliths at mantle depth or during transportation. In terms of δ⁷Li, the carbonatite and silicate melts produced remarkably contrasting δ⁷Li variations in olivine. Based on the systematic variations of Li abundances and Li isotopes in olivines, we suggest that the δ⁷Li value of olivine is a more important indicator than that of clinopyroxene in discriminating carbonatite and silicate melt interaction agents with peridotites.     

3D coupled scaled boundary finite-element/finite-element analysis of ground vibrations induced by underground train movement

When trains move through the tunnels, vibrations are generated and transmitted to the surrounding ground causing vibrations and noises in adjacent structures. The vibrations and noises can sometimes reach such a high level that can hardly be tolerated by the neighboring residents especially in densely populated urban environments. Consequently, the problem of train-induced vibrations has received increasing attention from both engineers and researchers. This paper presents the application of the scaled boundary finite-element method (SBFEM) to the 3D analysis of ground vibrations induced by underground trains. The media around the tunnel is simulated by the SBFEM. The train track is modeled using the finite-element method. 3D examples in both frequency and time domains are addressed to validate the accuracy and applicability of the method.