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Geothermobarometry of Askaoun Pluton in Ouzellarh-Sirwa Promontory (Central Anti-Atlas;Morocco)

Open Journal of Geology 2012年第3期2卷 136-147页

作者： Abdeslam Toummite moha Ikenne El Hassane Beraaouz Applied Geology and Environmental Geology Laboratory Faculty of Sciences Ibn Zohr University Agadir Morocco

Rocks of the late Neoproterozoic Askaoun pluton (558 ± 2 ma) located in the Ouzellarh-Sirwa promontory (Anti-Atlas) include magmatic microgranular enclaves (MMEs) ranging from rounded to ovoid in shape, dark and fine grained and generally 5 to 10 cm in size, some reaching a size of 50 cm. They are composed of microdiorite, quartz microdiorite and micromonzodiorite, whereas the felsic host rocks comprise mainly quartz-diorite and amphibole-biotite granodiorite based on mineralogical compositions. The mineral assemblage is similar to those described in their hosting granitoids but with different proportions. In this study composition of minerals is used to describe the nature of the magma and estimate the pressure, temperature and oxygen fugacity at which Askaoun pluton is emplaced. Based on chemistry of biotite Askaoun pluton formed from calc-alkaline magma. Compositions of plagioclase (An5 - An29);hornblende (Mg ≠= 0.59 - 0.65) and biotite (Mg ≠= 0.49 - 0.55) of MMEs are slightly distinct or similar to those of host rocks (An7-40;hbl Mg ≠= 0.64 - 0.69;Bi Mg ≠= 0.49 - 0.50) which suggest partial to complete equilibration during mafic-felsic magma interaction. The coexisting hornblende and plagioclase (hornblende-plagioclase thermometry), Al content in hornblende (aluminum-in-hornblende barometry) and the assemblage titanite-magnetite-quartz were used to constrain the P, T and fO2 during the crystallization of the parent magmas. The Askaoun pluton was emplaced at temperature ca. 504°C - 633°C and at pressure ca. 0.9 - 4.66 ± 0.6 Kbars (average depth = 6.5 km) from a highly oxidized magma (log fO2 = ?24.8 to ?19.2).

关键词： Askaoun Pluton MMEs Hornblende Thermobarometry Ouzellargh-Sirwa Promontory Anti-Atlas Morocco

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Changing patterns of hepatitis A prevalence within the Saudi population over the last 18 years

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World Journal of Gastroenterology 2008年第48期14卷 7371-7375页

作者： Faleh Al Faleh suliman Al Shehri Saleh Al Ansari mohammed Al Jeffri Yaqoub Al mazrou Ahmad Shaffi Ayman A Abdo Department of Medicine College of Medicine King Saud University Ministry of Education Ministry of Health Department of Community Medicine College of Medicine King Saud University

AIM： To determine the seroprevalence of Hepatitis A （HAV） amongst Saudi children and compare it with previously reported prevalence data from the same population. METHODS： A total of 1357 students were randomly selected between the ages of 16 and 18 years （689 males and 668 females） from three different regions of Saudi Arabia （madinah, AI-Qaseem, and Aseer） and tested for ***： The overall prevalence of anti-HAV-IgG among the study population was 18.6%. There was no difference between males and females but there was a significant difference in the seroprevalence （P = 0.0001） between the three different regions, with madinah region showing the highest prevalence （27.4%）. When classified according to socioeconomic status, lower class students had a prevalence of 36.6%, lower middle class 16.6%, upper middle class 9.6%, and upper class 5.9% （P = 0.0001）. Comparing the current study results with those of previous studies in 1989 and 1997 involving the same population, there was a marked reduction in the overall prevalence of HAV from 52% in 1989, to 25% in 1997, to 18.6% in 2008 （P 〈 0.0001）.CONCLUSION： Over the last 18 years, there has been a marked decline in the prevalence of HAV in Saudi children and adolescents. The current low prevalence rates call for strict adherence to vaccination policies in high-risk patients and raises the question of a universal HAV vaccination program.

关键词： Hepatitis A Saudi Arabia Epidemiology Prevalence Serology

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