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Open Journal of Geology 2016年第8期6卷 786-800页

作者： Arash Gourabjeiri-Pour Soraya Heuss-Aßbichler Mohsen Mobasheri Parivash Mahdavi Department of Geology Faculty of Science Miyane Branch Islamic Azad University Miyane Iran Department of Earth and Environmental Sciences Section for Mineralogy Petrology and Geochemistry Ludwig-Maximilians University Muenchen Germany Department of Petrology and Economic Geology School of Geosciences Shahrood University of Technology Shahrood Iran Department of Geology Faculty of Science Science and Research Branch Islamic Azad University Tehran Iran

The Gelmandeh Massive is located in the Central part of Iranian Microcontinent. Amphibolitic rocks occupy the main portion of Gelmandeh complex, which consists of hornblendite, garnet amphibolites, and gneiss. Geochemical investigations indicate that the ratio of Eu/Eu* separates samples into two categories: first category with ratio of Eu/Eu* > 1 and the second with ratio of Eu/Eu* < 1, which the former indicates an enriched mantle origin while the latter points to crustal contamination. Generally, amphibolites can be differentiated into two separate series. First series is characterized with calc-alkaline to alkaline composition with enriched mantle origin, and the second one has calc-alkaline to tholeiitic nature and it is of continental type that underwent crustal contamination within subduction zone. The microprobe electron analysis shows that the amphiboles were a member of the calcic group and hastingsite-tschermakite series. Geo-barometric studied and mineral paragenesis show that the metamorphism is of Barovian type with PT condition upto 7 K bar and 580°C.

关键词： Amphibolite Mineral Chemistry thermobarometry Gelmandeh Massive Boneh-Shorou Central Iran

Mineral Chemistry and thermobarometry of the Upper Eocene Volcanic Rocks in NE Tafresh, Iran

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Open Journal of Geology 2014年第12期4卷 612-621页

作者： Neda Baranpurian Mohamad Hashem Emami Mansor Vossoughi Abedini Rahim Dabiri Department of Geology Science and Research Branch Islamic Azad University Tehran Iran Department of Geology Islamshahr Branch Islamic Azad University Islamshahr Iran Department of Geology Mashhad Branch Islamic Azad University Mashhad Iran

Petrography and chemistry of minerals show that rocks of Upper Eocene in northeast of Tafresh are composed mostly of andesitic basalt, basaltic andesite and andesite volcanic rocks. Mineralogically these rocks are composed of phenocrystals of olivine, clinopyroxene and plagioclase and main texture of them is porphyry with cryptocrystalline or microcrystalline matrix. In addition, aphyric and pitted textures (amygdala) are also observed. According to the results of EPMA, phenocrystals of plagioclase in mentioned rocks include a range of anorthite to albite minerals. Alkali feldspars also contain a range of sodic to potassic minerals. Pyroxene crystals include hedenbergite, augite and hypersthene. Olivine minerals are often of the ferrohornblendite type. Based on thermobarometry it is estimated that to form clinopyroxene crystals of basaltic andesite rocks, temperature between 750°C to 1000°C is needed. Andesitic basalt rocks at higher temperature (1100°C) and andesite rocks at lower temperature (below 750°C) are formed. According to the distribution of aluminum in clinopyroxenes, these minerals at pressures less than 5 kbar and water content between 5% to 10% are crystallized. The mineral composition indicates that these rocks are formed in a tensional environment.

关键词： Volcanic Mineral Chemistry EPMA thermobarometry NE Tafresh

Tectonochemistry and p-t Conditions of Ramgarh and Almora Gneisses from Askot Klippe,Kumaun Lesser Himalaya

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Acta Geologica Sinica(English Edition) 2019年第2期93卷 322-343页

作者： Biraja P.DAS Mallickarjvm JOSHI Ashutosh KUM AR Centre of Advanced Study in Geology Institute of Science Banaras Hindu University

The chemical and petrological correlation of metamorphic nappes and klippes overlying the Proterozoic sedimentary units in the Kumaun Himalaya is still debated. The Ramgarh and Almora gneisses, not previously distinguished in the Askot Klippe, show distinct field, petrological and chemical signatures markedly similar to the tectonostratigraphic disposition of the Almora Nappe. A negative Eu anomaly in the Ramgarh granitic gneisses indicates lesser plagioclase fractionation while the Eu anomaly in the Almora pelitic gneisses is likely to have been controlled by feldspar crystallization in restites. During the anatexis at > 776°C temperature and >6.6 kbar pressure, the melt moved slightly away to its crystallization sites. The Rb/Sr ratio ?0.54 and Nb ?10 ppm is consistent with the granodioritic composition. The negative Sr anomaly in the underlying Ramgarh granitic gneisses indicates a distinct mantle derived source/plagioclase fractionation with a notable correspondence to other late orogenic granites, particularly the basement Ulleri gneisses from the Nepal Himalaya. Ramgarh gneisses plot in the late-and post-COLG field. The Askot ensemble is likely to be the tectonometamorphically reworked basement, viz. the Ramgarh Group along with its metapelitic cover o f the Almora Group, together comprising southward thrust remnants of the leading edge of the Indian Plate that collided with Tibet during the Tertiary Himalayan orogeny.

关键词： geochemistry thermobarometry Almora gneiss Ramgarh gneiss Almora Nappe Askot Klippe

Thermal State and Structure of the Lithosphere beneath Eastern China: A Synthesis on Basalt-Borne Xenoliths

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Journal of Earth Science 2010年第5期21卷 711-730页

作者：黄小龙徐义刚 Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences

Application of reliable thermobarometer on garnet-bearing mantle xenoliths and granulite xenoliths entrained by Cenozoic basalts in eastern China reveals two main types of geotherm. The first type, as exampled by Hannuoba （汉若坝）, Mingxi （明溪） and probably Northeast China, is characterized by constant slope of data in the P-T space. The second type, as exampled by the high geotherms of Niishan （女山） and probably Xinchang （新昌）, is characterized by variable slopes, with the samples with pressure 〈2 MPa defining a slow slope, whereas the samples with pressure 〉2 MPa define a virtually vertical slope. The different slopes in the second type of geotherm may correspond to different heat transfer mechanisms, with conductive transfer for the shallow upper mantle and advective transfer for the deep mantle. This observed transition in thermal transfer mechanism is consistent with theoretical modeling. The two types of geotherm are not mutually exclusive, because the second type may characterize the thermal state of whole lithospheric section including both mechanical boundary layer （MBL） and thermal boundary layer （TBL）, while the first type may only depict the MBL. The variable geotherms for different regions are indicative of a heterogeneous lithospheric structure in eastern China. （a） Eastern North China craton （NCC） is characterized by a second-type geotherm, corresponding to a thin lithosphere （-70 km）. Comparison of the equilibrium temperatures of spinel peridotites with this geotherm constrains the depth to Moho in eastern North China craton to be 30 kin. In contrast, western NCC （Hannuoba： the first-type geotherm） possesses a relatively low thermal gradient, indicative of a thick lithosphere （〉90-100 km） and a thick crust-mantle transition zone. The dramatic change in crustal and mantle structure across the DTGL （Daxing＇anling （大兴安岭）- Talhangshan （太行山） gravity lineament） is consistent with recent seismic studies. （b） There is a decrease in thermal gradient and in lithospheric thickness from the coast （Xinchang： the sec

关键词： geotherm thermobarometry garnet-bearing peridotite and pyroxenite granulite xenolith lithosphere eastern China.

Is the Songshugou Complex,Qinling Belt,China,an Eclogite Facies Neoproterozoic Ophiolite?

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Journal of Earth Science 2019年第3期30卷 460-475页

作者： Thomas Bader Lifei Zhang Xiaowei Li Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space Sciences Peking UniversityBeijing 100871 China State Key Laboratoiy of Geological Processes and Mineral Resources School of Earth Sciences and Resources China University of Geosciences Beijing 100083 China

Ophiolites play a key role in understanding subduction-accretion-collision processes. Herein, we discuss origin and metamorphic evolution of an enigmatic, Neoproterozoic ophiolite candidate—the mafic-ultramafic Songshugou Complex, Qinling belt, China—summarizing published thermobarometr);U/Pb geochronology, and geochemistry and presenting new phase equilibrium modeling. Garnet, rarely preserved in amphibolites of the Songshugou Complex, has prograde zoning and low-pvrope cores |Alm54-71(Grs+And)25-30PrP1-6Sps5-12. It formed at quartz eclogite facies conditions of 1.93-2.54 GPa, 462-542℃. During exhumation, garnet first was mantled by plagioclase-rich coronas at about 0.7-1.2 GPa, 660-710℃. During an isothermal uplift to 0.5-0.8 GPa, these coronas evolved widely into n-shaped aggregates and eventually into whitish ribbons oriented with a steeply southwest dipping mineral stretching lineation. The exhumation into middle-upper crustal levels proceeded till the Late Devonian. The oceanic protoliths of the eclogites were emplaced into continental crust in the Neoproterozoic and dragged into a subduction zone in North Qinling in the Cambrian. The ultramafic rocks of the Songshugou Complex were not subducted with the mafic rocks in a coherent block given the absence of garnet but ubiquitous occurrence of spinel implies a P maximum of ?1.7 GPa. Rather, mafic and ultramafic rocks belonged to downgoing and overriding plate, respectively. They were juxtaposed at 0.8-1.7 GPa at Early Ordovician time.

关键词： Qinling belt Songshugou Complex garnet isopleth thermobarometry eclogite Early Paleozoic

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

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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

Magma Mixing as a Trigger of Unzen's Volcano Eruptions

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地学前缘 2009年第S1期16卷 75-75页

作者： Ilya S.Fomin Pavel Plechov Petrology Department of Lomonosov's Moscow State University

Recent eruption in 1991-1995 years of Unzen Volcano(Kyushu Island,Japan)has caught attention of many volcanologists because of dramatical consequences of the previos eruption in 1792,when more than 15000 people were perished.So it is important to study this volcano and try to predict future eruptions and their possible damage.It is proved now,that magma hybridization processes

关键词： Unzen magma mixing mineral thermobarometry