Sub-arc mantle heterogeneity in oxygen isotopes: evidence from Permian mafic–ultramafic intrusions in the Central Asian Orogenic Belt

Integrated zircon–olivine O–Hf isotope data have been successfully used to unravel the nature of the source mantle for the early Permian post-collisional mafic–ultramafic intrusive rocks in the southern margin of the Central Asian Orogenic Belt in NW China. Olivine crystals with forsterite (Fo) contents varying from 91 to 87 mol% from the Permian Pobei mafic–ultramafic complex in the region yield highly elevated δ¹⁸O from 6.0 to 7.2‰. These values are much higher than typical mantle values (~?5.3‰) and are apparently at odds with the mantle-like ε_Nd(t) values of whole rocks (4.9–5.4). Magmatic zircon crystals from troctolite and gabbroic rocks show divergent oxygen and hafnium isotopic compositions: mantle-like ε_Hf(t) values from 5.1 to 11.9 and crust-like δ¹⁸O values from 7.6 to 10.1‰. The observed increase of δ¹⁸O values from olivine (an early crystallizing phase) to zircon (a late crystallizing phase) in the mafic–ultramafic rocks is generally consistent with an AFC process. However, this process cannot fully explain the highly elevated δ¹⁸O values (6–7‰) for the most primitive olivine containing Fo as high as mantle olivine (>?90 mol%) and the mantle-like Hf isotope composition of zircon. Mixing calculation indicates that such highly unusual isotope compositions can be explained by the previous source mantle contamination with subducted sediment-derived melts and slab-derived fluids. Our results show that the combination of zircon O–Hf isotopes and olivine oxygen isotopes is more effective than the data of zircon or olivine alone to distinguish the effect of AFC process from source contamination. The results from this study provide a new line of evidence that the sub-arc mantle is not homogeneous in oxygen isotopes.     

New Zr–Hf Geothermometer for Magmatic Zircons

A geothermometer equation \(T = \frac{{1531}} {{\ln K_d + 0.883}}\), where \(K_{\dot d} = \frac{{X_{Zr}^S X_{Hf}^m }} {{X_{Zr}^m X_{Hf}^s }}\) [X _j ⁱ is the concentration (in ppm) of component i in phase j] is the Zr and Hf distribution coefficient between melt and zircon, and T is temperature in K, was derived by thermodynamic processing of literature experimental data on Zr and Hf distribution between acid melts (m) and zircon (s) and on the solubility of zircon and hafnon in the melts with variable silica content. In calculations with this equations, we assumed the Zr concentration in zircon to be constant: 480000 ppm. It is shown that the commonly observed increase in Hf concentration from the cores to margins of magmatic zircon crystals is caused by the fractional crystallization of zircon. For differentiated acid magmatic series, the initial crystallization temperature of zircon in the least silicic cumulates should be evaluated using the cores of large zircon grains with the highest Zr/Hf ratio. Application of the geothermometer for mafic and intermediate rocks may be hampered due to simultaneous crystallization of zircon with some other ore and mafic minerals relatively enriched in Zr and Hf. The newly derived geothermometer has some advantages over other indicators of the crystallization temperature of magmatic zircon based on the zircon saturation index (Watson and Harrison, 1983; Boehnke et al., 2013) and on Ti concentration in this mineral (Ferry and Watson, 2007) as it does not depend on the major-oxide melt composition and on the accuracy of the estimated SiO₂ and TiO₂ activities in the melts. Calculations of the Zr and Hf fractionation trends in the course of zircon crystallization in granitoid melts allow one to evaluate the temperature at which more evolved melt portions were segregated.     

Recycling of sediment into the mantle source of K-rich mafic rocks: Sr–Nd–Hf–O isotopic evidence from the Fushui complex in the Qinling orogen

Potassium (K)-rich mafic rocks are viewed as being derived from partial melting of an enriched mantle source, but it is controversial about which processes cause the mantle enrichment. The Fushui intrusive complex is the largest early Paleozoic K-rich intrusive complex in the eastern Qinling orogen. Therefore, detailed studies on the Fushui complex can contribute not only to understanding of the petrogenesis of K-rich mafic rocks, but also to unraveling the Paleozoic evolution of the Qinling orogen. In this study, we provide an integrated investigation of in situ zircon U–Pb dating and Hf–O isotopes, in combination with whole-rock major and trace elements, as well as Sr–Nd–Hf isotopes, for the Fushui intrusive complex. In situ zircon secondary ion mass spectrometry (SIMS) / laser ablation induction coupled plasma mass spectrometry (LA-ICPMS) U–Pb dating reveals that different rock types of the Fushui complex have identical formation ages of 488–484 Ma. The Fushui complex belongs to the shoshonitic series, and is characterized by extreme large ion lithophile element (LILE, e.g., Ba, U, Th and Sr) and Pb enrichment and depletion of high field-strength elements (HFSEs, e.g. Nb, Ta, Zr, Hf, P and Ti). It shows high initial Sr isotopic ratios (0.7100–0.7151), negative whole-rock ε _Nd(t) (?3.97 to ?5.68) and negative to slight positive whole-rock (?2.24 to 2.38) and zircon (?2.85 to 0.34) ε _Hf(t) values, as well as high zircon δ¹⁸O values (6.86 ± 0.13 ‰). The Hf–Nd isotopic systems are decoupled with positive Δε _Hf values (3.85–5.37). These geochemical features indicate that the mantle source has incorporated subducted zircon–barren oceanic sediments. A simple two-end-members mixing model constrains the amount of subducted sediments in the Fushui mantle source to 5–8 %. The Fushui complex originated from 1 to 6 % equilibrium melting of a phlogopite-bearing garnet lherzolite by non-modal melting. As shoshonitic magmas have been discovered in modern nascent arcs, we suggest that the generation of the Fushui complex was induced by the subduction of the Paleotethyan Ocean, when it jumped from the northern to the southern boundary of the North Qinling microcontinent.     

Zircon Lu-Hf isotope systematics and U–Pb geochronology,whole-rock Sr-Nd isotopes and geochemistry of the early Jurassic Gokcedere pluton,Sakarya Zone-NE Turkey: a magmatic response to roll-back of the Paleo-Tethyan oceanic lithosphere

The early Mesozoic was a critical era for the geodynamic evolution of the Sakarya Zone as transition from accretion to collision events in the region. However, its complex evolutionary history is still debated. To address this issue, we present new in situ zircon U–Pb ages and Lu-Hf isotope data, whole-rock Sr-Nd isotopes, and mineral chemistry and geochemistry data of plutonic rocks to better understand the magmatic processes. The Gokcedere pluton is mainly composed of gabbro and gabbroic diorite. LA-ICP-MS zircon U–Pb dating reveals that the pluton was emplaced in the early Jurassic (177 Ma). These gabbros and gabbroic diorites are characterized by relatively low SiO₂ content of 47.09 to 57.15 wt% and high Mg# values varying from 46 to 75. The samples belong to the calc-alkaline series and exhibit a metaluminous I-type character. Moreover, they are slightly enriched in large ion lithophile elements (Rb, Ba, Th and K) and light rare earth elements and depleted in high field strength elements (Nb and Ti). Gabbroic rocks of the pluton have a depleted Sr-Nd isotopic composition, including low initial ⁸⁷Sr/⁸⁶Sr ranging from 0.705124 to 0.705599, relatively high ε _Nd (t) values varying from 0.1 to 3.5 and single-stage Nd model ages (T _DM1 = 0.65–0.95 Ga). In situ zircon analyses show that the rocks have variable and positive ε _Hf (t) values (4.6 to 13.5) and single-stage Hf model ages (T _DM1?=?0.30 to 0.65 Ga). Both the geochemical signature and Sr-Nd-Hf isotopic composition of the gabbroic rocks reveal that the magma of the studied rocks was formed by the partial melting of a depleted mantle wedge metasomatized by slab-derived fluids. The influence of slab fluids is mirrored by their trace-element characteristics. Trace-element modeling suggests that the primary magma was generated by a low and variable degree of partial melting (~5–15%) of a depleted and young lithospheric mantle wedge consisting of phlogopite- and spinel-bearing lherzolite. Heat to melt the mantle material was supplied by the ascendance of a hot asthenosphere triggered by the roll-back of the Paleo-Tethyan oceanic lithosphere. The rising melts were accompanied by fractional crystallization and encountered no or minor crustal contamination en route to the surface. Taking into account these geochemical data and integrating them with regional geological evidence, we propose a slab roll-back model; this model suggests that the Gokcedere gabbroic pluton originated in a back-arc extensional environment associated with the southward subduction of the Paleo-Tethyan oceanic lithosphere during the early Jurassic period. Such an extensional event led to the opening of the northern branch of the Neotethys as a back-arc basin. Consequently, we conclude that the gabbroic pluton was related to intensive extensional tectonic events, which peaked during the early Jurassic in response to the roll-back of Paleo-Tethyan oceanic slab in the final stage of oceanic closure.     

Sr,Nd, and Hf Isotope Composition of Rocks of the Reft Gabbro–Diorite–Tonalite Complex (Eastern Slope of the Middle Urals): Petrological and Geological Implications

This paper reports Rb–Sr and Sm–Nd isotope data on the gabbro–diorite–tonalite rock association of the Reft massif (eastern margin of the Middle Urals) and Lu–Hf isotope data on zircon populations from these rocks. In terms of Nd and Hf isotope composition, the rocks of the studied association are subdivided into two distinctly different groups. The first group consists of gabbros and diorites, as well as plagioclase granites from thin dikes and veins cutting across the gabbros. In terms of ⁴³Nd/¹⁴⁴Nd _i = 0.512518–0.512573 (ε_Nd(T) = +8.6...+9.7) and ¹⁷⁶Hf/¹⁷⁷Hf _i = 0.282961–0.283019 (ε_Hf(T) = +15.9...+17.9), these rocks are practically identical to depleted mantle. Their Nd and Hf model ages show wide variations, but in general are close to their crystallization time. The second group is represented by tonalites and quartz diorites, which compose a large body occupying over half of the massif area. These rocks are characterized by the lower values of ¹⁴³Nd/¹⁴⁴Nd _i = 0.512265–0.512388 (ε_Nd(T) = +3.7...+6.0) and ¹⁷⁶Hf/¹⁷⁷Hf _i = 0.282826–0.282870 (ε_Hf(T) = +11.1...+12.7). The T_DM values of the second group are much (two–three times) higher than their geological age (crystallization time), which indicates sufficiently long crustal residence time of their source. The initial ⁸⁷Sr/⁸⁶Sr in the rocks of both the groups varies from 0.70348 to 0.70495. This is likely explained by the different saturation of melts with fluid enriched in radiogenic Sr. The source of this fluid could be seawater that was buried in a subduction zone with oceanic sediments and released during slab dehydration. Obtained data make it possible to conclude that the formation of the studied gabbro–diorite–tonalite association is a result of spatially and temporally close magma formation processes in the crust and mantle, with insignificant contribution of differentiation of mantle basite magma.     

Community vulnerability to hazards: introducing local expert knowledge into the equation

The accuracies of three different evolutionary artificial neural network (ANN) approaches, ANN with genetic algorithm (ANN-GA), ANN with particle swarm optimization (ANN-PSO) and ANN with imperialist competitive algorithm (ANN-ICA), were compared in estimating groundwater levels (GWL) based on precipitation, evaporation and previous GWL data. The input combinations determined using auto-, partial auto- and cross-correlation analyses and tried for each model are: (i) GWL _t?1 and GWL _t?2; (ii) GWL _t?1, GWL _t?2 and P _t ; (iii) GWL _t?1, GWL _t?2 and E _t ; (iv) GWL _t?1, GWL _t?2, P _t and E _t ; (v) GWL _t?1, GWL _t?2 and P _t?1 where GWL _t , P _t and E _t indicate the GWL, precipitation and evaporation at time t, individually. The optimal ANN-GA, ANN-PSO and ANN-ICA models were obtained by trying various control parameters. The best accuracies of the ANN-GA, ANN-PSO and ANN-ICA models were obtained from input combination (i). The mean square error accuracies of the ANN-GA and ANN-ICA models were increased by 165 and 124% using ANN-PSO model. The results indicated that the ANN-PSO model performed better than the other models in modeling monthly groundwater levels.     

Optimal choice of the softening length and time step in <Emphasis Type="Italic">N</Emphasis>-body simulations

A criterion for the choice of optimal softening length ε for the potential and the choice of time step dt for N-body simulations of a collisionless stellar system is analyzed. Plummer and Hernquist spheres are used as models to analyze how changes in various parameters of an initially equilibrium stable model depend on ε and dt. These dependences are used to derive a criterion for choosing ε and dt. The resulting criterion is compared to Merritt’s criterion for choosing the softening length, which is based on minimizing the mean irregular force acting on a particle with unit mass. Our criterion for choosing ε and dt indicate that ε must be a factor of 1.5–2 smaller than the mean distance between particles in the densest regions to be resolved. The time step must always be adjusted to the chosen ε (the particle must, on average, travel a distance smaller than 0.5 ε during one time step). An algorithm for solving N-body problems with adaptive variations of the softening length is discussed in connection with the task of choosing ε, but is found not to be promising.     

New models to predict rock failure by linking the volume dilatant point with the peak stress point

The rock mass failure process can be divided into several distinct deformation stages: the compaction stage, elastic stage, stable failure stage, accelerated failure stage, and post-peak stage. Although each stage has been well studied, the relationship among the stages has not been established. Here, we establish two models which are the Strain model Q and Energy density model S by using the renormalization group theory and investigate the mechanical relationship between the volume dilatant point and peak stress point on the rock stress-strain curve. Our models show that the strain ratio (ε _f /ε _c ) and energy ratio (E _f /E _c ) at the volume dilatant point and peak stress point are solely functions of the shape parameter m. To verify our models, we further studied the failure process of rock specimens through several uniaxial compression experiments and found that the relationship between ε _f /ε _c or E _f /E _c and m shares a notably similar pattern to that from our theoretical model. However, the ε _f /ε _c and E _f /E _c values in our experiments are slightly smaller than those predicted by the models. In brief, we demonstrate that our models can be used to predict the failure process of the laboratory-scale hard brittle rock samples.     

Contrasting origin of two A-type rhyolite series from the Early Permian Nomgon bimodal volcanic association (Southern Mongolia)

A-type rhyolites of contrasting compositions and eruption characters were revealed among two volcanic series of the Early Permian bimodal association in the Nomgon graben. Rhyolites of the lower volcanic series formed extrusions, lava domes, and tuff horizons. They had low FeO_t, Zr, Hf, Nb, Ta, Y, and REE concentrations and also a moderately depleted Nd isotope composition (ε_Nd(Т) = 6.7–7.1). Their formation was related to anatexis of the juvenile continental crust, triggered by the thermal effect of mafic magmas. Rhyolites of the upper volcanic series formed extensive lava flows and dikes. Their composition was characterized by high FeO_t, Zr, Hf, Nb, Ta, Y, and REE concentrations, and also depleted Nd isotope characteristics (ε_Nd(Т) = 7.7–9.0). These rhyolite melts formed under long-term crystallizational differentiation of basaltoids in the intracrustal magmatic chambers, with limited participation of crustal contamination. The source of magmas for the upper volcanic series was the sublithospheric mantle.     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmospheres of the giants 25 Mon and HR 7389

An analysis of high-resolution CCD spectra of the giant 25 Mon, which shows signs of metallicity, and the normal giant HR 7389 is presented. The derived effective temperatures, gravitational accelerations, and microturbulence velocities are T_eff = 6700 K, log g = 3.24, and ξ _t = 3.1 km/s for 25 Mon and T_eff = 6630 K, log g = 3.71, and ξ _t = 2.6 km/s for HR 7389. The abundances (log ε) of nine elements are determined: carbon, nitrogen, oxygen, sodium, silicon, calcium, iron, nickel, and barium. The derived excess carbon abundances are 0.23 dex for 25 Mon and 0.16 dex for HR 7389. 25 Mon displays a modest (0.08 dex) oxygen excess, with the oxygen excess for HR 7389 being somewhat higher (0.15 dex). The nitrogen abundance is probably no lower than the solar value for both stars. The abundances of iron, sodium, calcium (for HR 7389), barium, and nickel exceed the solar values by 0.22–0.40 dex for both stars. The highest excess (0.62 dex) is exhibited by the calcium abundance for 25 Mon. Silicon displays a nearly solar abundance in both stars—small deficits of ?0.03 dex and ?0.07 dex for 25 Mon and HR 7389, respectively. No fundamental differences in the elemental abundances were found in the atmospheres of 25 Mon and HR 7389. Based on their T_eff and log g values, as well as theoretical calculations, A. Claret estimated the masses, radii, luminosities, and ages of 25 Mon (M/M_⊙ = 2.45, log(R/R_⊙) = 0.79, log(L/L_⊙) = 1.85, t = 5.3 × 10⁸ yr) and HR 7389 (M/M_⊙ = 2.36, log(R/R_⊙) = 0.50, log(L/L_⊙) = 1.24, t = 4.6 × 10⁸ yr), and also of the stars 20 Peg (M/M_⊙ = 2.36, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.79, t = 4.9 × 10⁸ yr) and 30 LMi (M/M_⊙ = 2.47, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.88, t = 4.8 × 10⁸ yr) studied by the author earlier.     

Petrogenesis of the Late Jurassic peraluminous biotite granites and muscovite-bearing granites in SE China: geochronological,elemental and Sr–Nd–O–Hf isotopic constraints

Biotite granites and muscovite-bearing granites are dominant rock types of the widespread granites in SE China. However, their petrogenesis has been enigmatic. A combined study of zircon U–Pb dating and Lu–Hf isotopes, whole-rock element geochemistry and Sr–Nd–O isotopes was performed for three late Mesozoic granitic plutons (Xinfengjie, Jiangbei and Dabu) in central Jiangxi province, SE China. All the plutons are composed of biotite granites and muscovite-bearing granites that have been poorly investigated previously. The new data not only allow us to assess their sources and magma evolution processes, but also helps us to better understand the genetic link to the large-scale polymetallic mineralization in SE China. LA-ICP-MS zircon U–Pb dating shows that three plutons were emplaced in the Late Jurassic (159–148 Ma) and that the muscovite-bearing granites are almost contemporaneous with the biotite granites. The biotite granites have SiO₂ contents of 70.3–74.4 wt% and are weakly to strongly peraluminous with ASI from 1.00 to 1.26, and show a general decrease in ASI with increasing SiO₂. They have relatively high zircon saturation temperatures (T _Zr = 707–817 °C, most > 745 °C) and show a general decrease in T _Zr with increasing SiO₂. They have high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7136 to 0.7166) and high δ¹⁸O values (9.1–12.8‰, most > 9.5‰) and clearly negative ε _Nd (T) (? 9.5 to ? 11.8) and ε _Hf (T) (in situ zircon) (? 13.1 to ? 13.5). The muscovite-bearing granites have high SiO₂ contents (74.7–78.2 wt%). They are also weakly to strongly peraluminous with ASI of 1.04–1.18 but show a general increase in ASI with increasing SiO₂. They have relatively low T _Zr (671–764 °C, most < 745 °C) and also show a general decrease in T _Zr with increasing SiO₂. The muscovite-bearing granites have high Rb (up to 810 ppm) and high (K₂O + Na₂O)/CaO (up to 270), Rb/Sr (up to 42) and Rb/Ba (up to 30) as well as low K/Rb (< 150, down to 50), Zr/Hf (< 24, down to 11) and Nb/Ta (< 6, down to 2). They show similar Nd–O–Hf isotopic compositions to the biotite granites with ε _Nd (T) of ? 8.7 to ? 12.0, δ¹⁸O of 8.7–13.0‰ (most > 9.5‰) and ε _Hf (T) (in situ zircon) of ? 11.3 to ? 13.1. Geochemical data suggest the origin of the biotite granites and muscovite-bearing granites as follows: Partial melting of Precambrian metasedimentary rocks (mainly two-mica schist) in the lower crust at temperatures of ca. 820 °C generated the melts of the less felsic biotite granites. Such primary crustal melts underwent biotite-dominant fractionation crystallization, forming the felsic biotite granites. Progressive plagioclase-dominant fractionation crystallization from the evolved biotite granites produced the more felsic muscovite-bearing granites. Thus, the biotite granites belong to the S-type whereas the muscovite-bearing granites are highly fractionated S-type granites. We further suggest that during the formation of the muscovite-bearing granites the fractional crystallization was accompanied by fluid fractionation and most likely the addition of internally derived mineralizing fluids. That is why the large-scale polymetallic mineralization is closely related to the muscovite-bearing granites rather than biotite granites in SE China. This is important to further understand the source and origin of biotite granites and muscovite-bearing granites in SE China even worldwide.     

Simulation of suspended sediment based on gamma test,heuristic, and regression-based techniques

In the present study, four different heuristic techniques viz. multi-layer perceptron (MLP), radial basis function (RBF), self-organizing maps (SOM), and co-active neuro-fuzzy inference system (CANFIS) with hyperbolic tangent and sigmoid transfer functions and two regression-based techniques, i.e., multiple linear regression (MLR) and sediment-rating curve (SRC), were used for suspended sediment modeling. Gamma test (GT), correlation function (CF), M test, and trail–error procedure were applied for estimation of appropriate input variables as well as training data length. The results of the GT and CF suggested the five input variables (Q_t, Q_t?1, Q_t?2, S_t?1, and S_t?2, where Q_t?1 and S_t?1 indicate the discharge and sediment values of one previous day) as the best combination. The optimal training data length (75% of total data) was estimated by M test and trail–error procedure for development of the applied models. The MLP with sigmoid transfer function (M-2) performed better than the all other models. The results of sensitivity analysis indicated that the present-day discharge (Q_t), 1-day lag discharge (Q_t?1) and 1-day lag suspended sediment (S_t?1) are the most influenced parameters in modeling current day suspended sediment (S_t).     

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).     

The age of the Nodular Limestone Formation (Late Cretaceous), Narmada Basin,central India

The age of the marine Nodular Limestone Formation of the Bagh Group is refined at Substage level through ammonoid and inoceramid index taxa. The study is based on the fresh collections from three well-defined successive intervals (Lower Karondia, Upper Karondia and Chirakhan members) of this formation having excellent exposures in different localities of the Narmada Basin, central India. The first record of the widely distributed Turonian ammonoid genera Spathites Kummel and Decker and Collignoniceras Breistroffer from the Nodular Limestone Formation constrained its age exclusively to Turonian. The Early Turonian species Spathites (Jeanrogericeras) aff. revelieranus (Courtiller) and Mytiloides labiatus (Sclotheim) occur in the lower part, while the Middle Turonian marker Collignoniceras cf. carolinum (d’Obrbigny) and Inoceramus hobetsensis (Nagao and Matsumoto) occurs in the upper part of the Karondia Member. The record of the index species Inoceramus teshioensis (Nagao and Matsumoto) in association with Placenticeras mintoi Vredenburg from Chirakhan Member allows a definite Late Turonian age. The present contribution is an attempt to resolve the controversies in the age of the Nodular Limestone Formation and also demarcation of the three divisions (Early, Middle and Late) of the Turonian Stage in the Narmada Basin, central India.     

Timescales for mechanisms for the dynamical evolution of open star clusters

We have obtained the stellar velocity dispersion in three mutually perpendicular directions in the halos and cores of clusters as a function of time for several non-stationary open-cluster models. During the dynamical evolution of the open-cluster models, the velocity dispersions undergo oscillations that do not decay during 5–10 violent-relaxation timescales, τ _vr . We estimated the time for synchronization of the rotation of the open-cluster models and their motion around the center of the Galaxy, t _s , which, depending on the model parameters, is t _s ? (5–27)τ _vr . Synchronization mechanisms for the models are discussed. The disruption of the systems in the force field of the Galaxy is strongly affected by tidal friction. We have also estimated the time for the formation of a spherical stellar-velocity distribution in the cluster models, t _σ ? (6 ? 25)τ _vr . The impact of instability in the stellar motions in a cluster on the formation of a spherical velocity distribution in the open-cluster models is discussed. We have noted a tendency for a weakening of the dependence of the coarse phase density of the cluster on small initial perturbations of the stellar phase coordinates in the model cluster cores for times about five times longer than the violent-relaxation time.     

Timing and source constraints on the relationship between mafic and felsic intrusions in the Emeishan large igneous province

Several I- and A-type granite, syenite plutons and spatially associated, giant Fe-Ti-V deposit-bearing mafic-ultramafic layered intrusions occur in the Pan-Xi (Panzhihua-Xichang) area within the inner zone of the Emeishan large igneous province (ELIP). These complexes are interpreted to be related to the Emeishan mantle plume. We present LA-ICP-MS and SIMS zircon U-Pb ages and Hf-Nd isotopic compositions for the gabbros, syenites and granites from these complexes. The dating shows that the age of the felsic intrusive magmatism (256.2 ± 3.0-259.8 ± 1.6 Ma) is indistinguishable from that of the mafic intrusive magmatism (255.4 ± 3.1-259.5 ± 2.7 Ma) and represents the final phase of a continuous magmatic episode that lasted no more than 10 Myr. The upper gabbros in the mafic-ultramafic intrusions are generally more isotopically enriched (lower ε_Nd and ε_Hf) than the middle and lower gabbros, suggesting that the upper gabbros have experienced a higher level of crustal contamination than the lower gabbros. The significantly positive ε_Hf(t) values of the A-type granites and syenites (+4.9 to +10.8) are higher than those of the upper gabbros of the associated mafic intrusion, which shows that they cannot be derived by fractional crystallization of these bodies. They are however identical to those of the mafic enclaves (+7.0 to +11.4) and middle and lower gabbros, implying that they are cogenetic. We suggest that they were generated by fractionation of large-volume, plume-related basaltic magmas that ponded deep in the crust. The deep-seated magma chamber erupted in two stages: the first near a density minimum in the basaltic fractionation trend and the second during the final stage of fractionation when the magma was a low density Fe-poor, Si-rich felsic magma. The basaltic magmas emplaced in the shallow-level magma chambers differentiated to form mafic-ultramafic layered intrusions accompanied by a small amount of crustal assimilation through roof melting. Evolved A-type granites (synenites and syenodiorites) were produced dominantly by crystallization in the deep crustal magma chamber. In contrast, the I-type granites have negative ε_Nd(t) [−6.3 to −7.5] and ε_Hf(t) [−1.3 to −6.7] values, with the Nd model ages () of 1.63−1.67 Ga and Hf model ages () of 1.56−1.58 Ga, suggesting that they were mainly derived from partial melting of Mesoproterozoic crust. In combination with previous studies, this study also shows that plume activity not only gave rise to reworking of ancient crust, but also significant growth of juvenile crust in the center of the ELIP.     

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).     

Effect of foliation orientation on the P- and S-wave velocity anisotropies and dynamic elastic constants of the quartz-micaschists metamorphic rocks,Angouran mine,Iran

Laboratory measurements are required to study geophysical properties of the subsurface because of lacking direct observation of Earth’s crust. In this research, compressional (P) and shear (S) wave velocity measurements have been conducted on cylindrical specimens of Quartz-micaschist cored using rock blocks taken from the zinc and lead Angouran mine, Zanjan, northwest of Iran. Cylindrical rock specimens were prepared from the blocks by coring in 0°, 30°, 45°, 60°, and 90° into the foliation direction. P- and S-wave velocities were measured along the cylindrical specimens with different foliation orientations. Percent variations of the P- and S-wave velocities (Thomsen’s anisotropic parameters ε and γ) and constant dynamic modulus of test results have been determined. Percent variations of the P-wave velocity (ε) increase with an increase of the foliation angle with respect to the propagating waves direction by a parabolic function as it shows P-wave velocity differences up to a maximum value of 50 %. Thomsen’s anisotropic parameter of γ has also the same function with the foliation angle. Meanwhile, foliation orientation has a much greater influence on ε than γ for foliation angle from 45° to 90° as \( \frac{\varepsilon }{\gamma } \) ratio increases with an increase of foliation angle. Values of dynamic elastic modulus (E), Poisson’s ratio (ν), shear modulus (μ), bulk modulus (K), and Lamé’s constant (λ) increase with the increase of foliation angle with the parabolic function. The results show that dynamic elastic modulus, Poisson’s ratio, shear modulus, bulk modulus, and Lamé’s constant have anisotropic behavior in relation with the foliation orientation.     

Strmömgren zones of type II supernovae

The emission measures EM in the directions of supernova remnants and pulsars are considered as functions of their ages t. The resulting plot has a well-defined lower boundary, which can be approximated by the expression EM_min∝1/t. The quantity EM_min increases with decreasing age t and does not level off or reach a maximum until t?500 yr. It is concluded that the bulk of the radiative energy that goes into ionizing and heating the interstellar gas is released at early stages of the supernova remnant’s evolution. We suggest that most of the kinetic energy of the supernova shell is converted into thermal energy and radiated at remnant ages t<100 yr, when the supernova shell, which is expanding at an enormous speed (about 10⁴ km/s), overtakes the shell produced by the presupernova in the supergiant stage. We have estimated the ionization energy E?10⁵¹ erg, diameter L?60 pc, and electron density N_e?7 cm^?3 of the HII regions around the supernovae (the supernova Strömgren zones). A list of objects that can be reliably identified as Strömgren zones of type II supernovae is presented. The plot of pulsar pulse broadening τ as a function of the pulsar age t also has a well-defined lower boundary, for which τ∝t^?2 when t≥1000 yr. This suggests that turbulence develops during the first thousand years after the supernova outburst. It is also concluded that turbulence plays an important role in the formation and evolution of the Strömgren zones of type II supernovae.     

A study of the supergiant 89 Her

We have used spectrograms taken with a dispersion of 8–12 Å per mm and Kurucz model atmospheres to study the supergiant 89 Her (F2Ibe).We find the effective temperature and gravity T _eff = 6300 ± 150 K and log g = 0.5 ± 0.2. We have analyzed the microturbulence in the star’s atmosphere based on FeI, FeII, and TiII lines, deriving ξ _t = 7.0 ± 0.5 km/s for the FeI and TiII lines and ξ _t = 8.0 ± 0.5 km/s for the FeII lines. Abundances were determined for 23 elements. The elemental abundances in the atmosphere of 89 Her show deficiencies compared to the solar chemical composition, except for sodium, which is overabundant relative to the Sun.