Uranium–lead ages of apatite from iron oxide ores of the Bafq District,East-Central Iran

Iron oxide–apatite (IOA) deposits, often referred to as Kiruna-type iron ore deposits, are known to have formed from the Proterozoic to the Tertiary. They are commonly associated with calc–alkaline volcanic rocks and regional- to deposit-scale metasomatic alteration. In the Bafq District in east Central Iran, economic iron oxide–apatite deposits occur within felsic volcanic tuffs and volcanosedimentary sequences of Early Cambrian age. In order to constrain the age of formation of these ores and their relationship with the Early Cambrian magmatic event, we have determined the U–Pb apatite age for five occurrences in the Bafq District. In a ²⁰⁶Pb/²³⁸U vs. ²⁰⁷Pb/²³⁵U diagram, apatite free of or poor in inclusions of other minerals plots along the Concordia between 539 and 527 Ma with four out of five samples from one deposit clustering at the upper end of this range. For this deposit, we interpret this cluster to represent the age of apatite formation, whereas the spread towards younger ages may reflect either minor Pb loss or several events of IOA formation. Apatite with inclusions of monazite (±xenotime) yields disturbed systems with inclusions having developed after formation of the iron ore–apatite deposits, possibly as late as 130–140 Ma ago. Obtained apatite ages confirms that (IOA) and the apatite-rich rocks (apatites) of the Bafq district formed coevally with the Early Cambrian magmatic (-metasomatic) events.     

A parametric study on seakeeping assessment of fast ships in conceptual design stage

The paper presents an approach to investigate the effects of some parameters on seakeeping assessment of fast ships in conceptual design stage. Hull form parameters have been classified into two groups: main dimensions (L, B and T) and secondary form parameters (LCB and C_P). To demonstrate the approach a fast ship is redesigned as parent hull and alternative hull forms are generated by changing these parameters systematically. Some hull forms are selected related the geometric limits and seakeeping analyzes are here investigated and discussed. The obtained results are satisfactory for seakeeping predictions during the conceptual design stage.     

Geological evolution of the West Luzon Basin (South China Sea,Philippines)

Interpretation of deep 2-D multi-channel seismic data sheds insights into the geological evolution of the West Luzon Basin, Philippines. This basin is a sediment-filled trough that is located between the island of Luzon and the outer arc high of the west Luzon subduction zone. High-amplitude, low-frequency reflection bands mark the acoustic basement. The basement, at about 6 s (TWT), is dissected by normal faults with some of them being inverted in a later phase of deformation. The sedimentary successions, overlying the basement are stratified with partly chaotic structures and discontinuous reflectors. Five regional unconformities separate major stratigraphic units. Grid calculations of our seismic data reveal variations in the sedimentation pattern of the basin with a shift of the deposition centre from east to west and backwards during formation. A distinct bottom-simulating reflector is commonly observed. Because the northern boundary of the continental fragments to the South of the West Luzon Basin is unclear we speculate that the basin may be (partly) underlain by continental crust. The continental crust was affected by rifting prior to and during the opening of the South China Sea and the basin was overprinted at a later stage by a forearc structural setting when subduction was initiated.     

Barremian–Danian chemostratigraphic sequences of the Cauvery Basin,India: Implications on scales of stratigraphic correlation

Chemostratigraphic concepts postulate that distinct chemozones could be recognized from rock records to help correlate geographically separated strata. Many studies have upheld this view, but were limited to classic boundaries such as Cenomanian–Turonian or Cretaceous–Tertiary. Only a few elements and isotopic compositions were made use in such studies. An attempt to recognize chemozones of Barremian–Danian strata of the Cauvery Basin, South India through whole-rock chemistry had revealed many complex signals and depositional events as expressed by bulk geochemical profiles. The signals indicate major shift in sedimentation pattern from dynamic depocenter to stable depositional conditions during Santonian. Varying sensitivities of different elements towards prevalent depositional conditions are also inferred. Trends of geochemical composition indicated domination of single depositional control all through the depositional history, basinal configuration that limited terrestrial sediment source and episodic influx of detrital materials. Presence of distinct change in whole-rock geochemistry across geochronological and lithostratigraphic boundaries is deciphered through a statistical tool ANOVA. These results demonstrate that visual delineation of chemozones in a long ranging rock record would be tenuous and has to be exercised with caution.     

Stratigraphy and palaeoenvironment of the Lower-“middle” Oligocene units in the northern part of the Western Taurides (İncesu area,Isparta, Turkey)

This study describes the stratigraphic and palaeoenvironmental significance of the Lower-“middle” Oligocene sediments based on the fauna from the Delikarkas? Formation and the microflora from the ?ncesu Formation of the ?ncesu area (northern part of the western Taurides, Isparta province, Turkey). In the area, the Oligocene sediments show a regressive succession, which begins with the limestones of the Delikarkas? Formation indicating marine conditions followed by conglomerates, sandstones and coaly mudstones of alluvial and fluvial (shallow marine-continental) origin. A well preserved foraminiferal assemblage including Nummulites intermedius, Nummulites vascus and Halkyardia maxima proves an Early Oligocene age for the Delikarkas? Formation. Due to palynological markers such as Boehlensipollis hohli, Slowakipollis hippophaëoides, Dicolpopollis kockelii, Magnolipollis neogenicus ssp. minor, Plicapollis pseudoexcelsus, Caryapollenites simplex and Intratriporopollenites instructus the ?ncesu Formation, which concordantly rests on the Delikarkas? Formation, may be assigned to the Early-“middle” Oligocene. From the palynomorph assemblage, three zones have been recognised according to abundance of species. Zone 1 is characterized by predominance of C. simplex and Momipites punctatus and rarely presence of tricolpate and tricolporate pollen. Zone 2 consists mainly of Inaperturopollenites dubius, Leiotriletes maxoides ssp. maximus, Verrucatosporites favus, Verrucatosporites alienus and infrequently marine dinoflagellate cysts. Zone 3 is characterized by a high percentage of ferns such as Echinatisporis?chattensis and Polypodiaceoisporites saxonicus. The presence of marine dinoflagellate cysts like Apectodinium sp. and Cleistosphaeridium sp., back-mangrove elements such as Acrostichum aureum and lepidocaryoid palms (e.g. Longapertites discordis, Longapertites punctatus and Longapertites psilatus) in the sediments of the ?ncesu Formation imply coastal or near-coastal conditions. Terrestrial palynomorphs in more inland settings were transported by running water towards the sea. Conifers are represented by poorly preserved and rare pollen grains of Pityosporites, Cathayapollis and Piceapollis which may have been transported by wind. In this study, the terrestrial climate of the ?ncesu Formation is also discussed on the basis of the Coexistence Approach method. The climate was warm at the coast (over 20 °C), as evidenced by A. aureum and lepidocaryoid palms, whereas there was a mean annual temperature of 17.2–17.4 °C must be assumed for the upland environment(s).     

Lattice-preferred orientations of late-Variscan granitoids derived from neutron diffraction data: implications for magma emplacement mechanisms

The lattice-preferred orientation (LPOs) of two late-Variscan granitoids, the Meissen monzonite and the Podlesí dyke granite, were determined from high-resolution time-of-flight neutron diffraction patterns gained at the diffractometer SKAT in Dubna, Russia. The results demonstrate that the method is suitable for the LPO analysis of polyphase, relatively coarse-grained (0.1–6 mm) rocks. The Meissen monzonite has a prominent shape-preferred orientation (SPO) of the non-equidimensional minerals feldspar, mica and amphibole, whereas SPO of the Podlesí granite is unapparent at the hand-specimen scale. The neutron diffraction data revealed distinct LPOs in both granitoids. The LPO of the non-equidimensional minerals feldspar, mica and amphibole developed mainly during magmatic flow. In the case of the Meissen monzonite, the magmatic flow was superimposed by regional shear tectonics, which, however, had no significant effect on the LPOs. In both samples, quartz shows a weak but distinct LPO, which is atypical for plastic deformation and different in the syn-kinematic Meissen monzonite and the post-kinematic Podlesí granite. We suggest that, first of all, the quartz LPO of the Meissen monzonite is the result of oriented growth in an anisotropic stress field. The quartz LPO of the Podlesí granite, which more or less resembles a deformational LPO in the flattening field of the local strain field, developed during magmatic flow, whereby the rhombohedral faces of the quartz crystals adhered to the (010) faces of aligned albite and to the (001) faces of zinnwaldite. Due to shape anisotropy of their attachments, the quartz crystals were passively aligned by magmatic flow. Thus, magmatic flow and oriented crystal growth are the major LPO-forming processes in both granitoids. For the Meissen monzonite, the solid-state flow was too weak to cause significant crystallographic re-orientation of the minerals aligned by magmatic flow. Finally, the significance of our results for the evaluation of the regional tectonic environment during magma emplacement is discussed. The discussion on the regional implications of the more methodologically oriented results provides the basis for future, more regionally aimed studies in view of the fabric characteristics of such plutons and their developing mechanisms.     

Preface: Proceedings of the 5th International Symposium on Lithographic Limestone and Plattenkalk

Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U–Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540 Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480–470 Ma, like many other “older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630 Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300 Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300–290 Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290–285 Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300–310 Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: “European” for Sambuco and “Briançonnais” for Maggia, separated by the “Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic unit.     

The fish fauna of the Late Jurassic Solothurn Turtle Limestone (NW Switzerland)

The surroundings of Solothurn (NW Switzerland) have been known for their fossil marine turtles since the beginning of the nineteenth century. In more recent history, access to the fossil bearing layers i.e. the Rätschenbank (Kimmeridgian, Late Jurassic) has not been possible until 1986 when one of the old quarries in the area re-opened. A series of excavations from 1986 to 1989 provided new material and a unique opportunity to re-investigate the fish fauna of the Solothurn Turtle Limestone that has not been dealt with since Agassiz (1833–1844). Examination and classification of the Solothurn specimens, mainly jaw fragments and teeth, furnished 11 species in 6 major groups: chimaeras (Ischyodus), selachians (Hybodus, Paracestracion, Asteracanthus), semionotids (Lepidotes), pycnodontids (Gyrodus, Proscinetes), caturids and oligopleurids (Caturus, Callopterus, Ionoscopus), and aspidorhynchids (Belonostomus).     

A new Jurassic cow shark (Chondrichthyes,Hexanchiformes) with comments on Jurassic hexanchiform systematics

A new taxon, ?Crassodontidanus gen. nov. of Hexanchiformes (cow sharks) from the Jurassic of Germany is described. It is characterized by peculiar teeth combining apomorphic (serrated mesial cutting edge of the main cusp) and plesiomorphic features (deep root with convex mesial and distal margins in labial and lingual views; protruding lingual root bulge). This character combination readily distinguishes members of the new taxon from all other known extant (Heptranchias, Hexanchus, Notorynchus) and extinct (?Gladioserratus, ?Notidanodon, ?Notidanoides, ?Pachyhexanchus, ?Paraheptranchias, ?Weltonia) hexanchiforms. Currently, two species, ?C. serratus (type species; Late Jurassic, Late Kimmeridgian of Nusplingen, South Germany) and ?C. wiedenrothi (Early Jurassic, Early Pliensbachian of Gretenberg (Hanover), North Germany) are assigned to this taxon. ?Crassodontidanus gen. nov. is member of ?Crassonotidae fam. nov. and sister to ?Notidanoides Maisey, 1986 and ?Pachyhexanchus Cappetta, 1990. We consider ?Notidanus amalthei Oppel, 1854 from the Pliensbachian of South Germany, ?Notidanus insignis Seguenza, 1887 from the Oxfordian of Sicily (Italy) and ?Notidanus wagneri Agassiz, 1843 from the Early Tithonian of Solnhofen (South Germany) nomina dubia and nomina nuda, respectively. The family ?Crassonotidae comprises plesiomorphic hexanchiforms ranging from the Sinemurian (Early Jurassic) to the Hauterivian (Early Cretaceous).     

中亚造山带东段铀、钼矿床分布与中间地块的关系

在近年来中亚造山带东段多金属矿床研究取得新进展的基础上,选择铀、钼两类矿床,结合铀、钼元素的地球化学行为探讨成矿物质来源的多样性和成矿的多阶段演化。此外,从构造研究角度,结合中亚造山带东段中大量中间地块存在的构造现象,讨论中间地块与成矿作用的关系:中间地块经历了从大陆边缘的裂解、漂移和板块碰撞造山作用,在漫长而复杂的地质过程中遭受的多次改造,有利成矿物质的反复被萃取和聚集。最后提出印支期华北克拉通北缘和北部造山带的成矿作用与底侵背景下的伸展作用密切相关。