Geochemistry and tectonomagatic setting of Tertiary volcanic rocks of the Kangan area, northeast of Sarbisheh, southern Khorasan

Introduction The study area is located 12km away from the north east of Sarbisheh at the eastern border of the Lut block (Karimpour et al., 2011; Richards et al., 2012). The magmatic activity in the Lut blockhas begun in the middle Jurassic (165-162 Ma) and reached its peak in the Tertiary age (Jung et al., 1983; Karimpour et al., 2011). Volcanic and subvolcanic rocks in the Tertiary age cover over half of the Lut block with up to 2000 m thickness and they were formed due to subduction prior to the collision of the Arabian and Asian plates (Jung et al., 1983; Karimpour et al., 2011). In the Kangan area, the basaltic lavas cropped out beyond the above intermediate to acid volcanic rocks. In this area, bentonite and perlite deposits have an economic importance. The main purpose of this paper is to present a better understanding of the tectono-magmatic settings of volcanic rocks in the northeast of Sarbisheh, east of Iran based on their geochemical characteristics. Materials and methods Fifteen samples were analyzed for major elements by inductively coupled plasma (ICP) technologies and trace elements by using inductively coupled plasma mass spectrometry (ICP-MS), following a lithium metaborate/tetraborate fusion and nitric acid total digestion, at the Acme laboratories, Vancouver, Canada. Results The Kangan area is located at the northeast of Sarbishe, Southern Khorasan and the eastern border of the Lut block. In this area, basaltic lavas have cropped out above intermediate to acid lavas such as andesite, dacite, rhyolite (sometimes perlitic) .The main minerals in the basalt are plagioclase, olivine and pyroxene, in andesite contain plagioclase, pyroxene, biotite and amphibole and in acid rocks include plagioclase, quartz, sanidine, biotite and amphibole. Intermediate to acid rocks have medium to high-K calc-alkaline nature and basalt is alkaline. Enrichment in LREE relative to HREE (Ce/Yb= 21.14-28.7), high ratio of Zr/Y(4.79- 10.81), enrichment in LILE and negative anomaly of Eu, Nb, P, Ti, Ba and Sr in intermediate to acid lavas are characteristics of subduction related calc-alkaline magmatism. Geochemical characteristics such as high ratio of La/Yb (8.18), low content of Rb with tectonic setting discriminant diagrams show within plate environment for basalt. The constituent magma of the studied rocks originated from an enriched garnet lherzolite source in 100 to 110km depth. Discussion Enrichment in LREE relative to HREE (Ce/Yb= 21.14-28.7), high ratio of Zr/Y (4.79- 10.81), enrichment in LILE and negative anomaly of Eu, Nb, P, Ti, Ba and Sr in intermediate to acid lavas are characteristics of subduction related calc-alkaline magmatism. Tectonic setting discrimination diagrams show that andesite to dacitic rocks are located in active continental margin (Schandle and Gorton, 2002) and basalt is placed within the volcanic plate zone and continental rift type (Verma et al., 2006). Intermediate to acid rocks of Kangan area originated from lithospheric mantle (Moharami et al., 2014) that is enriched by sediment melt related metasomatism (Ersoy et al., 2010) whereas Kangan basaltic lava origin is Nb enriched (Wang et al., 2008; Sajona et al., 1996) mixed lithospheric - asthenospheric mantle (Moharamiet al., 2014). According to the trace elements diagrams (Ellam, 1992), partial melting depth for generation of Kangan area lavas was determined to be about 100 to 110Km. Because of absent crustal contamination instances in the basalt, it can be argued that ascending of magma has been rapid and probably similar to other alkali basalts in east of Iran, it may be related to deep fault systems. Acknowledgements The authors would like to thank the reviewers for their constructive comments which greatly contributed to the improvement of the manuscript. References Ellam, R.M., 1992. Lithospheric thickness as a control on basalt geochemistry. Geology, 20(2): 153-156. Ersoy, E.Y., Helvaci, C. and Palmer, M.R., 2010. Mantle source characteristics and melting models for the early-middle Miocene mafic volcanism in western Anatolia: implications for enrichment processes of mantle lithosphere and origin of K-rich volcanism in post-collisional settings. Journal of Volcanology and Geothermal Research, 198(1-2): 112-128. Jung, D., Keller, J., Khorasani, R., Marcks, C., Baumann, A. and Horn, P., 1983. Petrology of the Tertiary magmatic activity the northern Lut area, East of Iran. Geological Survey of Iran, Tehran, Report 51, 519 pp. Karimpour, M.H., Stern, C.R., Farmer, L., Saadat, S. and Malekezadeh, A., 2011. Review of age, Rb-Sr geochemistry and petrogenesis of Jurassic to Quaternary igneous rocks in Lut block, eastern Iran. Geopersia, 1(1):19-36. Moharami, F., Azadi, I., Mirmohamadi, M., Mehdipour Ghazi, J. and Rahgoshay, M., 2014. Petrological and Geodynamical Constraints of Chaldoran Basaltic Rocks, NW Iran: Evidence from Geochemical Characteris. Iranian Journal of Earth Sciences, 6(1): 31-43. Richards, J.P., Spell, T., Rameh, E., Razique, A. and Fletcher, T., 2012. High Sr/Y magmas reflect arc maturity, high magmatic water content, and porphyry Cu ± Mo ± Au potential: examples from the Tethyan arcs of central and eastern Iran and western Pakistan. Economic Geology, 107(2): 295–332. Sajona, F.G., Maury, R.C., Bellon, H., Cotton, J. and Defant, M., 1996. High field strength element enrichment of Pliocene-Pelistocene island arc basalts, Zomboanga Peninsula, Western Mindanao Philippines. Journal of Petrology, 37(3): 693–726. Schandl, E.S. and Gorton, M.P., 2002. Application of high field strength elements to discriminate tectonic setting in VMS environment. Economic Geology, 97(3): 629-642. Verma, S.P., Guevara, M. and Agrawal, S., 2006. Discriminating four tectonic settings: Five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log- ratio transformation of major-element data. Journal of Earth System Science, 115(5): 485-528. Wang, Q., Wyman, D.A., Xu, J., Wan, Y., Li, C., Zi, F., Jiang, Z., Qiu, H., Chu, Z., Zhao, Z. and Dong, Y., 2008. Triassic Nb-enriched basalts, magnesian andesites, and adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by slab-derived melts in the mantle wedge. Contributions to Mineralogy and Petrology, 155(4): 437-490

Prevalence and risk factors of seizure in children with acute bacterial meningitis: an update epidemiologic study

Abstract Objective The current study aimed to investigate the prevalence and risk factorsof seizure in acute bacterial meningitis. Materials & MethodsIn the present study, a total of 180 children (age range, 2 months to 14 years) with acute bacterial meningitis, were separated into two groups based on the diagnosis of seizure. The study was conducted in Mashhad (Iran) from 2002 to 2016. Results Seizure occurred in 37.4% of children with bacterial meningitis. Streptococcus pneumonia (S. pneumonia) was the most common organism. Most of the children with seizures (53.7%) had more than one episode. Also, 35% of patients had neurologic complications. Complications were more related to the seizure occurrence, the number of episodes, prolonged seizure, and being younger than 12 months. Age categories of less than 1 year and 1-5 year were associated with increased risk of seizure (odds ratio: 4.33 and 6.54, respectively). The more episode of seizure was associated with more complications (odds ratio: 6.33). Conclusion The prevalence of seizure in acute bacterial meningitis was 37.4%. Because of association between seizure and complication, it is necessary to pay more attention to the exact and on-time diagnosis of bacterial meningitis

Petrogenesis and zircon U-Pb dating of skarnified pyroxene-bearing dioritic rocks in Bisheh area, south of Birjand, eastern Iran

Introduction The study area is located 196 km south of Birjand in eastern border of the Lut block )Berberian and King, 1981) in eastern Iran between 59°05′35" and 59°09′12" E longitude and 31°42′29" and 31°44′13" N latitude. The magmatic activity in the Lut block began in the middle Jurassic such as Kalateh Ahani, Shah Kuh and Surkh Kuh granitoids that are among the oldest rocks exposed within the Lut block (Esmaeily et al., 2005; Tarkian et al., 1983; Moradi Noghondar et al., 2011-2012). Eastern Iran, and particularly the Lut block, has great potential for different types of mineralization as skarnification in Bisheh area which has been studied in this paper. The goal of this study is to highlight the geochronology, geochemistry of major and trace elements, Rb-Sr, Sm-Nd isotopes for skarnified pyroxene-bearing diorites. Materials and methods Major element compositions of thirteen samples were determined by wavelength-dispersive X-ray fluorescence (XRF) spectrometry, using fused discs and the Phillips PW 1410 XRF spectrometer at Ferdowsi University, Mashhad, Iran. These samples were analysed for trace elements using inductively coupled plasma-mass spectrometry (ICP-MS) in the Acme Analytical Laboratories, Vancouver, British Columbia, Canada. Zircon grains were separated from pyroxene diorite porphyrys using heavy liquid and magnetic techniques at the Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan. Zircon U-Pb dating was performed by laser ablation-inductively-coupled plasma-mass spectrometry (LA-ICP-MS), using an Agilent 7500 s machine and a New Wave UP213 laser ablation system, equipped at the Dr Shen-Su Sun memorial laboratory in the Department of Geosciences, National Taiwan University, Taiwan. Strontium and Nd isotopic analyses were performed on a six-collector Finnigan MAT 261 thermal-ionization mass spectrometer at the University of Colorado, Boulder, Colorado, United States. 87Sr/86Sr ratios were determined using four-collector static mode measurements. Several measurements of SRM-987 during the study period yielded a mean of 87Sr/86Sr = 0.71032 ± 2 (error is the 2σ mean). Measured 87Sr/86Sr ratios were corrected to SRM-987 = 0.71028. Measured 143Nd/144Nd was normalized to 146Nd/144Nd = 0.7219. Analyses were conducted as dynamic mode, three-collector measurements. Several measurements of the La Jolla Nd standard during the study period yielded a mean of 143Nd/144Nd = 0.511838 ± 8 (error is the 2σ mean). Results In the Bisheh area that is located east of Lut block, pyroxene-bearing dioritic rocks are high-K calk-alkaline and meta-aluminous. Primitive mantle-normalized trace element spider diagrams display strong enrichment in LILE, such as Rb, Ba, and Cs, and depletion in some HFSE, e.g., Nb, P, Ti, Y and Yb. Chondrite-normalized REE diagrams show (La/Yb)N ratios ranging from 7.75 to 8.63 and small negative Eu anomalies. These features along with high Th/Yb and Ta/Yb ratios show that magmatism is related to continental margin subduction. Obvious depletion of Nb and Ti, relatively high values of Mg#, initial 87Sr/86Sr (0.70606) and 143Nd/144Nd (0.512424) ratios as well as εNd (-3.05) suggest that the magma originated from an enriched mantle with crustal contamination. High values of Rb, Th and K and low amount of P and Ti support the magma contamination in upper crust during magma evolution. Zircon U-Pb age dating for a porphyritic pyroxene diorite sample yield an age of 44.07±0.69 Ma indicating middle Eocene (Lutetian). Discussion The isotopic value for the Bisheh dioritic porphyry can be considered as indicative of lithospheric mantle melting. The trace element characteristics of these rocks can be used to characterize their mantle source. The MORB normalized trace element pattern (Pearce, 1983) of all samples shows a negative anomaly for Nb, Ti and Ta. The negative anomaly of these elements can be explained by the presence of a residual TNT phase (Ti-Nb-Ta, e.g., rutile, ilmenite and perovskite) during the melting of the source (Reagan and Gill, 1989). This pattern followed that of calc-alkaline magmas derived from a sub-arc mantle, with scarce or no garnet in the source. Furthermore, Bisheh subvolcanic bodies were enriched in Rb, Ba and Th, indicating that they had experienced interaction with the continental crust (Kuşcu et al., 2002). The chondrite-normalized rare earth element pattern of the studied rocks shows a high ratio of light rare earth elements (LREE) to heavy rare earth elements (HREE). All the samples have been plotted in the VAG field. The dioritic rocks from the Bisheh have relatively high Mg# (0.4-0.56), which is consistent with derivation from mantle melts contaminated by continental crust (Rapp and Watson, 1995). The initial 87Sr/86Sr of Bisheh pyroxene diorite porphyry was 0.70606 and the (143Nd/144Nd)i isotope compositions and εNd value of these rocks was 0.512424 and -3.05, respectively. These values show that the magma originated from an enriched mantle with crustal contamination. Acknowledgements The authors are grateful to Professor Sun-Lin Chung from the Department of Geosciences, National Taiwan University, for supporting the researchers in the use of U-Th-Pb zircon age dating. References Berberian, M. and King, G.C., 1981. Towards a palaeogeography and tectonics evolution of Iran. Canadian Journal of Earth Science, 18(2): 210–265. Esmaeily, D., Nedelec, A., Valizadeh, M.V., Moore, F. and Cotton, J., 2005. Petrology of the Jurassic Shah-Kuh granite (eastern Iran), with reference to tin mineralization. Journal of Asian Earth Sciences, 25(6): 961-980. Tarkian, M., Lotfi, M. and Baumann, A., 1983. Tectonic, magmatism and the formation of mineral deposits in the central Lut, east Iran. Geological Survey of Iran, geodynamic project (geotraverse) in Iran, Tehran, Report 51, 519 pp. Moradi Noghondar, M., Karimpour, M.H., Farmer, G.L. and Stern, C.R., 2011-2012. Sr-Nd isotopic characteristic, U-Pb zircon geochronology, and petrogenesis of Najmabad Granodiorite batholith, Eastern Iran. Journal of Economic Geology, 3(2): 127-145. (in Persian) Pearce, J.A., 1983. Role of the sub-continental lithosphere in magma genesis at active continental margins. In: C.J. Hawkesworth and M. J. Norry (Editors), Continental basalts and mantle xenoliths. Shiva Publications, Nantwich, UK, pp. 230-249. Reagan, M. K. and Gill, J. B., 1989. Coexisting calcalkaline and high niobium basalts from Turrialba volcano, Costa Rica: implication for residual titanates in arc magma source. Journal of Geophysical Research, 94(B4): 4619-4633. Kuşcu, I., Kuşcu, G.G., Meinert, L.D. and Floyd, P.A., 2002. Tectonic setting and petrogenesis of the Çelebi granitoid, (Kirikkale-Turkey) and comparison with world skarn granitoids. Journal of Geochemical Exploration, 76(3): 175–194. Rapp, R.P. and Watson, E.B., 1995. Dehydration melting of metabasalt at 8–32 kbar: Implications for continental growth and crust–mantle recycling. Journal of Petrology, 36(4): 891–931. <br