DOCSLIB.ORG

Origin of Tholeitic Intermediate Rocks in the Early Cretaceous Comei LIP

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Origin of Tholeitic Intermediate Rocks in the Early Cretaceous Comei LIP МИНИСТЕРСТВО НАУКИ И ВЫСШЕГО ОБРАЗОВАНИЯ РОССИЙСКОЙ ФЕДЕРАЦИИ НАЦИОНАЛЬНЫЙ ИССЛЕДОВАТЕЛЬСКИЙ ТОМСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ ПРАВИТЕЛЬСТВО РОССИЙСКОЙ ФЕДЕРАЦИИ РОССИЙСКИЙ ФОНД ФУНДАМЕНТАЛЬНЫХ ИССЛЕДОВАНИЙ Петрология магматических и метаморфических комплексов Выпуск 10 Материалы X Всероссийской конференции с международным участием 27 ноября - 30 ноября 2018 года ЛАБТЕСТ BTESCAN А. LABTEST Томск 2018 ORIGIN OF THOLEIITIC INTERMEDIATE ROCKS IN THE EARLY CRETACEOUS COMEI LIP, SE TIBET Ying Xia1’ 3, Di-Cheng Zhu1, R. E. Ernst2- 3 1 State Key Laboratory o f Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China 2 Department o f Earth Sciences, Carleton University, Ottawa K1S5B6, Canada 3 Department o f Geology and Geography, Tomsk State University, Tomsk, Russia A newly found tholeiitic intrusive suite in Chigu Tso of the Comei LIP (large igneous province), S E Tibet, provides new insight into the petrogenesis of tholeiitic intermediate rocks in LIPs. Zircon U-Pb dating results suggest that Chigu Tso intrusive suite is coeval to the Comei LIP at c. 132 Ma. The compositions of Chigu Tso intrusive suite exhibit a compositional continuum from dolerite, diorite to tonalite (SiO2=51.2-62.6 wt %). M ass balance calculations suggest that high FeO^/MgO (> 3.4) tholeiitic intermediate rocks (diorites and tonalites) in Chigu Tso could be generated by large degrees (~60-85 wt %) of fractional crystallization from low FeO^/MgO (~0.7) primary magmas. The occurrence of significant amounts of halogen-rich amphibole in tholeiitic intermediate rocks indicates volatile-rich conditions in the late differentiation stage and requires a prolonged shallow crustal magma chamber provides room for cooling and differentiation (up to 75 wt % fractional crystallization). Extensional stress field in rift zones are not favorable to generate shallow crustal magma chamber which results in limited site for producing highly evolved tholeiitic intermediate rock. The paucity of intermediate rocks in LIPs suggest that most silicic rocks should derived from partial melting of rather than fractional crystallization of basaltic materials. Key words; tholeiitic intermediate rocks; fractional crystallization; amphibole; Comei LIP; S E Tibet A large igneous province (LIP) is the manifestation of exten­ remains enigmatic. LIPs are mainly tholeiitic basalts (Bryan, Er­ sive mafic magmatism (> O.lMkm2 and > 0.1 Mkm3) in a short nst, 2008). If fractional crystallization of tholeiitic basalts could duration (< 5 Ma) pulse (or in some cases multiple pulses), and produce tholeiitic intermediate rocks, then the following question with intraplate characteristics (Coffin, Eldhoim, 1994; Bryan, is why tholeiitic intermediate rocks are so rare in LIPs? Ernst’ 2008; Ernst, 2014). LIPs are dominantly mafic composi­ Previous equilibrium crystallization experiments of anhy­ tions, but also show significant compositional variations form ul­ drous tholeiitic basalts provide little constraint on the generation tramafic to silicic. Both globally and regionally, the distribution of tholeiitic intermediate rocks (e.g. Grove, Bryan, 1983; Yang of SiO2 content in LIPs is bimodal with chemical groupings at et. al., 1996). Recently, fractional crystallization experiments of 45-56 wt % and 65-75 wt % (Bryan, Ernst, 2008; Bryan, Ferrari, low FeO'/MgO (~0.5) anhydrous tholeiitic basalts suggest that 2013). The paucity of intermediate compositions in LIPs, gener­ tholeiitic intermediate rocks are generated at very late fraction­ ally recognized as “Bunsen-Daly gap”, is frequently manifested ation stage (> 80 wt %) by crystallization of spinel and plagi- as bimodal suites in the field (e.g. Kirstein et. al., 2000; Ewart et. oclase at 1.0 GPa and ilmenite at 0.7 GPa, resulting in FeO'/ al., 2004; Pinto et. al., 2011). Generation of such a silica gap is a MgO >2.6 and >22, respectively (Villiger et. al., 2004, 2007). subject of much debate, with focus on the origin of silicic rocks However, fractional crystallization of primary magmas during derived from partial melting of basaltic precursors or lower crust magma ascent through the crust or storage in staging chambers is (e.g. Suneson, Lucchitta, 1983; Mahoney et. al., 2008; Colon et. a polybaric process (Putirka, Condit, 2003; Putirka et. al., 2009; al., 2018), fractional crystallization from basaltic melts (e.g. Ay- Putirka, 2017; Hole, 2018) which is difficult to simulate accu­ alew et. al., 2002; Shellnutt, Jahn, 2010; Hutchison et. al., 2016) rately by laboratory experiments. More investigations, in particu­ or silicate-liquid immiscibility (e.g. McBirney, Nakamura, 1974; lar integrated natural examples of tholeiitic intermediate rocks, Jakobsen et. al., 2005). However, the occurrence and petrogene­ are needed for better understanding the generation of tholeiitic sis of intermediate rocks has been ignored. intermediate rocks in LIPs. Here, we offer a case study from the Although intermediate rocks are volumetrically minor in Comei LIP. LIPs (Bryan, Ernst, 2008), previous studies provide important This study focus on a compositional diverse tholeiitic intru­ constraints on the petrogenesis of these rocks (e.g. Lightfoot et. sive suite including dolerite, diorite and tonalite dykes and sills in al., 1987; Turner et. al., 1999; Ewart et. al., 2004; Natali et. al., Chigu Tso, central Comei LIP, SE Tibet. Zircon U-Pb age dating 2013). Intermediate rocks in LIPs are mainly alkaline rocks (e.g. results suggest Chigu Tso intrusive suite is coeval to the Comei syenite, trachyte and trachyandesite) with subordinate tholeiitic LIP at c. 132 Ma. Mass balance calculations suggest that the high and calc-alkaline andesites and trachyandesites (Fig. 1a). Based FeO‘/MgO tholeiitic intermediate rocks (diorites and tonalites) upon field and geochemical relations to the associated basalts, al­ in Chigu Tso are highly evolved magmas which could be gen­ kaline and tholeiitic intermediate rocks are commonly interpret­ erated at the late differentiation stage from low FeO‘/MgO pri­ ed as a consequence of fractional crystallization from basaltic mary magma by amphibole-dominated fractional crystallization magmas, possibly with the involvement of crustal contamination (Fig. 2). Large amounts of halogen-rich amphiboles in tholeiitic (Holland, Brown, 1972; Turner et. al., 1999; Natali et. al., 2013; intermediate rocks indicate a volatile-rich condition in the late Owen-Smith et. al., 2013). Calc-alkaline intermediate rocks are differentiation stage which may result from progressing frac­ characterized by low FeO'/MgO ratios (Fig. 1b) which are likely tional crystallization (Fig. 3). Such large degrees of fractional to derive from metasomatized sub-continental lithosphere man­ crystallization of the tholeiitic intermediate rocks require magma tle (SCLM) (Cai et. al., 2010; Zhang et. al., 2013). Tholeiitic chamber in shallow crust (Putirka, 2009). intermediate rocks are characterized by higher FeO'/MgO ratios However, LIPs are generally associated with continental breakup than calc-alkaline intermediate rocks in continental arcs (Fig. and formation of new ocean basins, proving the critical role of rift­ lb). However, where and how tholeiitic intermediate rocks form ing (White, Mckenzie, 1989; CourtiUot et. al., 1999; Ernst, 2014). 32 Fig. 1. (a) Total alkalis vs silica diagram (Le Bas et. al., 1986) indicating intermediate rocks (56-65 wt %), such as andesite, syenite, latite, trachyte and trachyandesite, are predominately alkaline in LIPs [e.g. Central Atlantic Magmatic Province (Eby et. al., 1992; Sundeen et. al., 1992; Kennedy, Stix, 2007), Deccan (Tiwari, 1971; Lightfoot et. al., 1987; Devey, Stephens, 1992; Owen-Smith et. al., 2013), Emeishan (Zhou et. al., 2008; Cai et. al., 2010), Ethiopian Plateau (Kieffer et. al., 2004; Natali et. al., 2013), North Atlantic (Deer 1976; Holland, Brown, 1972); Parana-Etendeka (Piccirillo et. al., 1989; Turner et. al., 1999; Kirstein et. al., 2000; Ewart et. al., 2004; Marsh, Milner, 2007; Hartmann et. al., 2012) and Tarim (Zhang et. al., 2013; Zou et. al., 2015)]. (b) FeOt/MgO vs SiO2 diagram (Miyashiro, 1974) indicates that tholeiitic intermediate rocks have higher FeOt/MgO ratios than calc-alkaline intermediate rocks in LIPs and Andean arc (Barragan et. al., 1998; Samaniego et. al., 2005). I, B = Irvine, Baragar (1971). 33 Fig. 2. Mass balance calculations showing fractionation o f different mineral assemblages controlled the variation o f major elments from primary magma to the most evolved Chigu Tso tonalite. The tholeiitic intermediate compositions could be generated by a three- step fractional crystallization from primary magma. Stage 1: fractional crystallization o f 34 wt % mineral assemblages o f 96% olivine and 4% Cr-spinel from primary magma result in a composition of FeOt/MgO~2.2, MgO~6.54 wt % and SiO2~51.4 wt %, which may be the parental magam o f Cona OIB-type mafic rocks, Sangxiu basalts and Chigu Tso intrusive sutie. Stage 2: fractional crystallization o f 35 wt % of mineral assemblages o f 59% clinopyroxene, 33% plagioclase and 8% ilmenite from the end-product in stage 1 produce a composition o f FeOt/MgO~3.4, MgO~5.1 wt % andSiO2~53.0 wt %) which is similar to evolved Chigu Tso diorites. Stage 3: fractional crystallization o f 60 wt % o f mineral assemblages of 65% amphibole, 27% plagioclase and 8% ilmenite from the end-product in stage 2 generate a compositon o f FeOt/MgO~6.7, MgO~2.4 wt % and SiO2~63.5 wt %, which is similar
Load more

Recommended publications
  • Li in Plagioclase: Investigating Its Rapid Diffusion and Potential As
    Goldschmidt Conference Abstracts 2009 A181 Li in plagioclase: Investigating its Uranium minerals from a Portuguese rapid diffusion and potential as Variscan granite and its geospeedometer hydrothermal alteration 1,2 1 M.E.J.A. CABATO*, R. ALTHERR AND T. LUDWIG M.M.S. CABRAL PINTO , M.M.V.G. SILVA , 1 3 3 A.M.R. NEIVA , F. GUIMARÃES AND P.B. SILVA Mineralogie, Institut für Geowissenschaften, Universität- Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, 1Center of Geosciences, Department of Earth Sciences, Germany University of Coimbra, Portugal ([email protected]) (*correspondence: [email protected]) 2Department of Geosciences, University of Aveiro, Portugal 3LNEG–National Laboratory of Energy and Geology, 4466- Elemental and isotopic studies with Li as a geochemical 956 S. Mamede de Infesta, Portugal tracer for source components and potential tool for geospeedometry have proliferated in recent years. Indeed, the Electron microscopy images, X-ray maps and electron abundance and isotopic fractionation of Li, alongside its rather microprobe analyses were carried out on uraninite, coffinite, (meta)saleeite, thorite, xenotime, monazite and apatite from rapid diffusivity especially in plagioclase, remain topics of unaltered and altered Variscan peraluminous granite and interest and importance. In volcanic systems, such Li data may related hydrothermal brecciated uranium-quartz veins. demonstrate processes and timescales that lead up to the Uraninite occurs mainly in the unaltered granite [1], is rare in extrusion of magma. the altered granite and was not found in the mineralized quartz To further understand Li diffusion in (and out of) veins. Uraninite from the altered granite is fractured and plagioclase, we analyse exceptionally large crystals using the hydrated, has the radioactive damage halos filled with late SIMS, to be confirmed by other methods.
    [Show full text]
  • (REFC) Magma Chambers: Implications for Differ
    Available online at www.sciencedirect.com ScienceDirect Geochimica et Cosmochimica Acta 143 (2014) 8–22 www.elsevier.com/locate/gca Modeling the compositional evolution of recharging, evacuating, and fractionating (REFC) magma chambers: Implications for differentiation of arc magmas Cin-Ty A. Lee a,⇑, Tien Chang Lee b, Chi-Tang Wu a a Dept. of Earth Science, MS-126 Rice University, 6100 Main St., Houston, TX 77005, United States b Dept. of Earth Sciences, University of California, Riverside, CA 92521, United States Available online 25 August 2013 Abstract Equations are presented to describe the compositional evolution of magma chambers undergoing simultaneous recharge (R), evacuation (E), and fractional crystallization (FC). Constant mass magma chambers undergoing REFC will eventually approach a steady state composition due to the “buffering” effect of recharging magma. Steady state composition is attained after 3/(Dax + ae) overturns of the magma chamber, where D is the bulk solid/melt partition coefficient for the element of interest and ax and ae are the proportions of crystallization and eruption/evacuation relative to the recharge rate. Steady state composition is given by Cre/(Dax + ae). For low evacuation rates, steady state concentration and the time to reach steady state scale inversely with D. Compatible (D > 1) elements reach steady state faster than incompatible (D < 1) elements. Thus, mag- ma chambers undergoing REFC will eventually evolve towards high incompatible element enrichments for a given depletion in a compatible element compared to magma chambers undergoing pure fractional crystallization. For example, REFC mag- ma chambers will evolve to high incompatible element concentrations for a given MgO content compared to fractional crys- tallization.
    [Show full text]
  • Geothermal Country Update for Ecuador, 2005 -2010
    Proceedings World Geothermal Congress 2010 Bali, Indonesia, 25-29 April 2010 Geothermal Country Update for Ecuador, 2005 -2010 Bernardo Beate, Rodney Salgado Escuela Politécnica Nacional, Dpto. de Geología, PO Box 17-01-2759, Quito/Ecuador [email protected] Keywords: Ecuador, geothermal exploration, heat sources, already completed the first geothermal gradient exploration hot springs of Ecuador, assessment of geothermal hole, ever, in Ecuador, on the Tufiño prospect, to a depth of prospects, use of geothermal energy. 554 m and final diameter NQ (76 mm). Chachimbiro has been allocated 1 MUSD for geophysical exploration ABSTRACT starting 2009 and reconnaissance geological and geochemical surveys are underway in Chacana-Papallacta Ecuador is located on the active convergent plate margin of prospect. This and several other high and low-medium Southamerica, which is characterized by a broad continental temperature geothermal prospects in Ecuador await state volcanic arc with abundant active volcanoes and intense and private investment to be developed in order to lessen seismicity. Earlier geothermal exploration, carried out from the dependance on fossil fuel use. Finally, in Ecuador, the mid 1970’s to the earlier 1990’s by government geothermal energy is challenged to be cost-efficient in front institutions with the aid of foreign technical assistance of an abundant hydro resource, as well as to be programs, defined a combined theoretical potential of about environmentally safe. 500 MWe for the three most promising geothermal prospects, namely: Tufiño-Chiles, Chalupas and Chachimbiro, located in the highlands of central-north 1. INTRODUCTION Ecuador. A dozen of other geothermal prospects, related to This paper is a follow up of the previous country update for silicic calderas, or to evolved stratovolcanoes, or even to the interval 2000-2005, published in the Proceedings of evolved basaltic shields, like Alcedo in Galapagos, will WGC2005 in Antalya, Turkey (Beate & Salgado, 2005).
    [Show full text]
  • The Central Atlantic Magmatic Province (CAMP) in Morocco
    The Central Atlantic Magmatic Province (CAMP) in Morocco Andrea Marzoli, Hervé Bertrand, Nasrrddine Youbi, Sara Callegaro, Renaud Merle, Laurie Reisberg, Massimo Chiaradia, Sarah Brownlee, Fred Jourdan, Alberto Zanetti, et al. To cite this version: Andrea Marzoli, Hervé Bertrand, Nasrrddine Youbi, Sara Callegaro, Renaud Merle, et al.. The Central Atlantic Magmatic Province (CAMP) in Morocco. Journal of Petrology, Oxford University Press (OUP), 2019, 60 (5), pp.945-996. 10.1093/petrology/egz021. hal-02405965 HAL Id: hal-02405965 https://hal.univ-lorraine.fr/hal-02405965 Submitted on 12 Dec 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. J OURNAL OF Journal of Petrology, 2019, Vol. 60, No. 5, 945–996 doi: 10.1093/petrology/egz021 P ETROLOGY Advance Access Publication Date: 19 April 2019 Original Article The Central Atlantic Magmatic Province (CAMP) in Morocco Andrea Marzoli 1*, Herve´ Bertrand2, Nasrrddine Youbi3,4, Downloaded from https://academic.oup.com/petrology/article-abstract/60/5/945/5475177 by guest on 13 December 2019 Sara Callegaro 5, Renaud Merle6, Laurie Reisberg7, Massimo Chiaradia8, Sarah I. Brownlee9, Fred Jourdan10, Alberto Zanetti11, Joshua H.F.L. Davies8†, Tiberio Cuppone1, Abdelkader Mahmoudi12, Fida Medina13, Paul R.
    [Show full text]
  • Crustal Thickness Control on Sr/Y Signatures of Recent Arc Magmas
    OPEN Crustal thickness control on Sr/Y SUBJECT AREAS: signatures of recent arc magmas: an PETROLOGY GEOCHEMISTRY Earth scale perspective Massimo Chiaradia Received 4 November 2014 Section of Earth and Environmental Sciences, University of Geneva, Rue des Maraıˆchers 13, 1205 Geneva, Switzerland. Accepted 7 January 2015 Arc magmas originate in subduction zones as partial melts of the mantle, induced by aqueous fluids/melts Published liberated by the subducted slab. Subsequently, they rise through and evolve within the overriding plate crust. 29 January 2015 Aside from broadly similar features that distinguish them from magmas of other geodynamic settings (e.g., mid-ocean ridges, intraplate), arc magmas display variably high Sr/Y values. Elucidating the debated origin of high Sr/Y signatures in arc magmas, whether due to mantle-source, slab melting or intracrustal processes, is instrumental for models of crustal growth and ore genesis. Here, using a statistical treatment of .23000 Correspondence and whole rock geochemical data, I show that average Sr/Y values and degree of maturation (MgO depletion at requests for materials peak Sr/Y values) of 19 out of 22 Pliocene-Quaternary arcs correlate positively with arc thickness. This should be addressed to suggests that crustal thickness exerts a first order control on the Sr/Y variability of arc magmas through the M.C. (Massimo. stabilization or destabilization of mineral phases that fractionate Sr (plagioclase) and Y (amphibole 6 garnet). In fact, the stability of these mineral phases is function of the pressure at which magma evolves, [email protected]) which depends on crustal thickness. The data presented show also that high Sr/Y Pliocene-Quaternary intermediate-felsic arc rocks have a distinct origin from their Archean counterparts.
    [Show full text]
  • Seyed Amir Mohammad Razavi Khosroshahi
    Geology, geochemistry, geochronology, and economic potential of the Taftan volcanic complex, southeastern Iran by Seyed Amir Mohammad Razavi Khosroshahi A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Earth and Atmospheric Sciences University of Alberta © Seyed Amir Mohammad Razavi Khosroshahi, 2015 Abstract The late Miocene-Quaternary Taftan volcanic complex is located above the Makran subduction zone in Sistan and Baluchestan province of southeastern Iran. The earliest volcanic eruptions at Taftan started in the late Miocene (~8 Ma) by explosive eruption of andesitic to dacitic lava on the Cretaceous to Eocene volcanic and sedimentary paleosurface ~20 km to the northwest of the current edifice. Later Plio-Pleistocene volcanism consisted of voluminous andesitic and dacitic lavas and pyroclastic flows (~3.1-0.4 Ma). The major and trace element compositions of the Taftan volcanic rocks show calc-alkaline to high-K calc-alkaline affinity with depletions of Nb, Ta, and Ti and relative enrichment of large-ion lithophile elements (LILE) and Th and U; these are typical signatures of subduction-related arc magmas. From the late Miocene to the late Pleistocene La/Yb and Sr/Y ratios of the Taftan volcanic rocks increase, which likely reflects fractional crystallization of pyroxene and amphibole. Electron microprobe analysis of amphibole phenocrysts from the Taftan volcanic rocks show that amphibole chemistry changed from high-Al pargasite to low-Al magnesio-amphibole from the late Miocene to the Pleistocene. Detailed modelling of amphibole chemistry indicates that the host magmas were water saturated (>5 wt.% H2O) and underwent partial crystallization at various depths between ~20 to ~5 km in the upper crust prior to eruption.
    [Show full text]
  • Geothermal Country Update for Ecuador, 2000-2005
    Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005 Geothermal Country Update for Ecuador, 2000-2005 Bernardo Beate, Rodney Salgado Escuela Politecnica Nacional, Dept de Recursos Minerales, PO Box 17-01-2759, Quito/Ecuador [email protected] Keywords: Ecuador, geothermal exploration, heat source, The energy market is dominated by Hydro (50.6 %) and hot springs of Ecuador, assessment of geothermal prospects, Fossil Fuel (49.4 %) generation, with a total installed use of geothermal energy. capacity of 3451 Mwe, yielding a gross electricity production of 12357 GWh/yr (as of Dec 2002). ABSTRACT Production from renewable energy sources in Ecuador, Due mainly to its favorable geodynamic setting along the including geothermal, solar and wind, is still neglegible, but active convergent plate margin of Southamerica, is planned to increase in the future. The Tufiño-Chiles characterized by a broad continental volcanic arc with geothermal prospect owns the especial status of Bi-National numerous active volcanoes and intense seismicity, and to Project, due to its location on the Ecuador-Colombia border. the elevated oil prices of the time, Ecuador started the This and several other high and low-medium temperature exploration of its geothermal resources about 30 years ago, geothermal prospects in Ecuador await state and private aiming on high enthalpy prospects, suitable for electricity investment to be developed in order to lessen the production. dependence on fossil fuel use. Finally, in Ecuador, geothermal energy is challenged to be cost-efficient in front Exploration for geothermal resources was carried out from of an abundant hydro resource, as well as to be the mid 1970´s through the early 1990´s by ecuadorean environmentally safe.
    [Show full text]
  • Article Reference
    Article Why large porphyry Cu deposits like high Sr/Y magmas? CHIARADIA, Massimo, et al. Reference CHIARADIA, Massimo, et al. Why large porphyry Cu deposits like high Sr/Y magmas? Scientific Reports, 2012, vol. 2 DOI : 10.1038/srep00685 Available at: http://archive-ouverte.unige.ch/unige:27594 Disclaimer: layout of this document may differ from the published version. 1 / 1 Why large porphyry Cu deposits like high Sr/Y magmas? SUBJECT AREAS: Massimo Chiaradia1, Alexey Ulianov2, Kalin Kouzmanov1 & Bernardo Beate3 PETROLOGY EARTH SCIENCES 1Section of Earth and Environmental Sciences, University of Geneva, 1205 Geneva, Switzerland, 2Institute of Mineralogy and GEOCHEMISTRY Geochemistry, University of Lausanne, 1015 Lausanne, Switzerland, 3Escuela Polite´cnica Nacional, Dep.to de Geologı´a, Ladro´nde MINERALOGY Guevara E11-253, Quito, Ecuador. Received Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they 19 March 2012 are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is Accepted essential to develop genetic models that can be used for exploration purposes. Here we present results on a 10 September 2012 Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at Published depths of ,15 km from high Sr/Y (.70) andesitic magmas before sulphide saturation. This lends support to 24 September 2012 the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits.
    [Show full text]
  • Why Large Porphyry Cu Deposits Like High Sr/Y Magmas?
    Why large porphyry Cu deposits like high Sr/Y magmas? SUBJECT AREAS: Massimo Chiaradia1, Alexey Ulianov2, Kalin Kouzmanov1 & Bernardo Beate3 PETROLOGY EARTH SCIENCES 1Section of Earth and Environmental Sciences, University of Geneva, 1205 Geneva, Switzerland, 2Institute of Mineralogy and GEOCHEMISTRY Geochemistry, University of Lausanne, 1015 Lausanne, Switzerland, 3Escuela Polite´cnica Nacional, Dep.to de Geologı´a, Ladro´nde MINERALOGY Guevara E11-253, Quito, Ecuador. Received Porphyry systems supply most copper and significant gold to our economy. Recent studies indicate that they 19 March 2012 are frequently associated with high Sr/Y magmatic rocks, but the meaning of this association remains elusive. Understanding the association between high Sr/Y magmatic rocks and porphyry-type deposits is Accepted essential to develop genetic models that can be used for exploration purposes. Here we present results on a 10 September 2012 Pleistocene volcano of Ecuador that highlight the behaviour of copper in magmas with variable (but generally high) Sr/Y values. We provide indirect evidence for Cu partitioning into a fluid phase exsolved at Published depths of ,15 km from high Sr/Y (.70) andesitic magmas before sulphide saturation. This lends support to 24 September 2012 the hypothesis that large amounts of Cu- and S-bearing fluids can be accumulated into and released from a long-lived high Sr/Y deep andesitic reservoir to a shallower magmatic-hydrothermal system with the potential of generating large porphyry-type deposits. Correspondence and requests for materials hree-quarters of the world’s Cu and one-fifth of the world’s Au are currently supplied by porphyry should be addressed to systems1.
    [Show full text]
  • Notice Concerning Copyright Restrictions
    NOTICE CONCERNING COPYRIGHT RESTRICTIONS This document may contain copyrighted materials. These materials have been made available for use in research, teaching, and private study, but may not be used for any commercial purpose. Users may not otherwise copy, reproduce, retransmit, distribute, publish, commercially exploit or otherwise transfer any material. The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specific conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research." If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement. This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Geothermal Resources Council Transactions,Vol. 22, September 20-23, 1998 The Chalupas and Chachimbiro Geothermal Fields in Ecuador Eduardo Aguilera Espe, Sangolqui-Ecuador ABSTRACT The geological setting as well as a preliminary geothermal geographic and physiographic zone corresponds to the core of model of two of the main geothermal areas of Ecuador are pre- the Ecuadorian Andes. It is characterized by two paralell moun- sented in this paper. The assessment is based only on surface tain ranges or Cordillera Occidental (to the west) and the exploration activities. It is likely that, because of the presence Cordillera Real (to the east) separated by a narrow valley, the of abundant highly differentiated volcanic products of recent Interandean Depression, which disappears towards the south.
    [Show full text]
  • Universite Blaise Pascal Ecole Doctorale Des
    No d’Ordre : D.U. 2593 UNIVERSITE BLAISE PASCAL U.F.R. Sciences et Technologies ECOLE DOCTORALE DES SCIENCES FONDAMENTALES No 830 THESE présentée pour obtenir le grade de DOCTEUR D’UNIVERSITE Spécialité : Géochimie - Volcanologie Par : KÜLAHCI DOĞAN G. Deniz Master Le volcanisme basaltique post-collisionnel d’Anatolie Centrale Etude chronologique, magmatologique et géochimique Evolution spatio-temporelle Soutenue publiquement le 1 Septembre 2015, devant le commission d’examen President : LE PENNEC Jean-Luc Université Blaise Pascal Clermont-Ferrand Rapporteur : GUILLOU Hervé LSCE CEA-CNRS- Gif-Sur-Yvette Rapporteur : SEYİTOĞLU Gürol Université d'Ankara - Ankara Examinateur : KÜRKÇÜOĞLU Biltan Université Hacettepe- Ankara Examinateur : MURATÇAY VAROL Elif Université Hacettepe- Ankara Directeur de thèse : TEMEL Abidin Université Hacettepe- Ankara Co-directeur de thèse : GOURGAUD Alain Université Blaise Pascal Clermont-Ferrand Le volcanisme basaltique post-collisionnel d’Anatolie Centrale Etude chronologique, magmatologique et géochimique Evolution spatio-temporelle Résumé Cette thèse est consacrée à la caractérisation pétrologique et géochimique des basaltes quaternaires post-collisionnels d’Anatolie centrale (strato-volcans Erciyes et Hasandağ et volcanisme dispersé d'Obruk-Zengen et de Karapınar), en se focalisant sur l’évolution spatio-temporelle de ce magmatisme de la Cappadoce (Turquie). Par la géochronologie K-Ar, la coexistence de basaltes alcalins et calco-alcalins a été démontrée, parfois dans un même lieu et à la même époque. Par ailleurs, nos résultats montrent aussi que ces basaltes peuvent être très jeunes (quelques milliers d’années seulement). La minéralogie des basaltes quaternaires de la Cappadoce est la suivante : plagioclase, olivine, clinopyroxène, orthopyroxène et oxydes (magnétite, ilménite). Pourtant, seuls les basaltes de l’Erciyes contiennent de l’orthopyroxène, alors que ceux du Hasandağ et du volcanisme dispersé d’Obruk-Zengen et de Karapınar en sont dépourvus.
    [Show full text]
  • Quaternary Sanukitoid-Like Andesites Generated by Intracrustal Processes (Chacana Caldera Complex, Ecuador): Implications for Archean Sanukitoids
    JOURNAL OF PETROLOGY VOLUME 55 NUMBER 4 PAGES 769^802 2014 doi:10.1093/petrology/egu006 Quaternary Sanukitoid-like Andesites Generated by Intracrustal Processes (Chacana Caldera Complex, Ecuador): Implications for Archean Sanukitoids MASSIMO CHIARADIA1*, OTHMAR MU«NTENER2 AND BERNARDO BEATE3 1SECTION OF EARTH AND ENVIRONMENTAL SCIENCES, UNIVERSITY OF GENEVA, RUE DES MARAI“ CHERS 13, 1205 GENEVA, SWITZERLAND 2INSTITUTE OF EARTH SCIENCES, UNIVERSITY OF LAUSANNE, GE¤OPOLIS, 1015 LAUSANNE, SWITZERLAND 3DEPARTMENT OF GEOLOGY, ESCUELA POLITECNICA NACIO¤NAL, QUITO, ECUADOR RECEIVED MAY 27, 2013; ACCEPTED JANUARY 21, 2014 High-Mg diorites enriched in incompatible elements and their extru- associated with predominant silica-rich (adakite-like) andesites, sive equivalents are rare subduction-related rock types that have been which are widespread throughout the Quaternary arc of Ecuador. found in modern arc settings and in Late Archean sequences, where This makes the Quaternary Ecuadorian magmatic province a close they are associated with trondhjemite^tonalite^granodiorite equivalent of the Archean TTG^sanukitoid association. The bulk- (TTG) suites. Archean rocks with these geochemical features are rock geochemistry, petrography and mineral chemistry data indicate known as sanukitoids and, despite their limited abundance, are con- that the sanukitoid-like features of the andesites of the Yuyos flow sidered to be the indicators of the onset of modern plate tectonics derive from intracrustal recycling of the felsic^intermediate to because of their similarities to modern subduction-related high-Mg mafic^ultramafic roots of the Quaternary volcanic arc of Ecuador andesites and diorites. Understanding the genesis of sanukitoid by ‘normal’ mantle-derived basaltic magmas with the geochemical rocks is thus an essential step towards understanding crustal growth characteristics of continental arc basalts or high-alumina basalts.
    [Show full text]