DOCSLIB.ORG

Can Slab Melting Be Caused by Flat Subduction? Geology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Can Slab Melting Be Caused by Flat Subduction? Geology See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/234073692 Can slab melting be caused by flat subduction? Geology Article in Geology · June 2000 DOI: 10.1130/0091-7613(2000)28<535:CSMBCB>2.0.CO;2 CITATIONS READS 428 1,167 4 authors, including: M.-A. Gutscher René C Maury Université de Bretagne Occidentale Université de Bretagne Occidentale 164 PUBLICATIONS 5,573 CITATIONS 356 PUBLICATIONS 11,783 CITATIONS SEE PROFILE SEE PROFILE Erwan Bourdon CFG Services 38 PUBLICATIONS 1,092 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: ACTIVEMARGINS View project Eastern Indonesian Geodynamic Evolution View project All content following this page was uploaded by M.-A. Gutscher on 20 May 2014. The user has requested enhancement of the downloaded file. Can slab melting be caused by flat subduction? Marc-André Gutscher* Laboratoire GTS, UMR 5573, Université Montpellier II, F-34095 Montpellier, France René Maury IUEM/Université Bretagne Occidentale, Place Nicolas Copernic, F-29280 Plouzané, France Jean-Philippe Eissen IRD Centre de Bretagne, B.P. 70, F-29280 Plouzané, France Erwan Bourdon ABSTRACT tion of adakitic magmas for these cases, related to Slab melting has been suggested as a likely source of adakitic arc magmas (i.e., andesitic an unusual subduction geometry known as flat and dacitic magmas strongly depleted in Y and heavy rare earth elements). Existing numerical subduction (Fig. 3) (Sacks, 1983; Pennington, and petrologic models, however, restrict partial melting to very young (<5 Ma) oceanic crust 1984; Cahill and Isacks, 1992; Abbott et al., (typically at 60–80 km depth). Paradoxically, most of the known Pliocene-Quaternary adakite 1994; Gutscher et al., 1999a, 2000). Of the 10 occurrences are related to subduction of 10–45 Ma lithosphere, which should not be able to melt known flat slab regions worldwide (Fig. 1), 8 are under normal subduction-zone thermal gradients. We propose an unusual mode of subduction linked to present or recent (<6 Ma) occurrences known as flat subduction, occurring in ~10% of the world’s convergent margins, that can pro- of adakitic magmas (Table 1). duce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat subduction regions worldwide, eight are linked to present or recent GEODYNAMIC MODEL (<6 Ma) occurrences of adakitic magmas. Observations from Chile, Ecuador, and Costa Rica Comparative observations from several well- suggest a three-stage evolution: (1) steep subduction produces a narrow calc-alkaline arc, typi- constrained flat slab regions along the Andean cally ~300 km from the trench, above the asthenospheric wedge; (2) once flat subduction begins, and Central American margin suggest a three- the lower plate travels several hundred kilometers at nearly the same depth, thus remaining in stage evolution illustrating how a reduction of a pressure-temperature window allowing slab melting over this broad distance; and (3) once flat slab dip can lead to episodes of slab melting. In subduction continues for several million years, the asthenospheric wedge disappears, and a vol- the normal situation, a narrow calc-alkaline arc canic gap results, as in modern-day central Chile or Peru. The proposed hypothesis, which (volcanic line) develops above a steeply dipping reconciles thermal models with geochemical observations, has broad implications for the study slab, commonly between the 100 and 150 km iso- of arc magmatism and for the thermal evolution of convergent margins. depth contours to the subducted plate (Fig. 3A). When the dip of the downgoing plate flattens, Keywords: flat subduction, thermal structure, slab melting, adakites. in response to a change in buoyancy (i.e., sub- duction of overthickened oceanic crust), the INTRODUCTION doxically, of the ~20 known occurrences of arc typically widens, extending much farther Petrologic models suggest that formation of adakites worldwide, only 5 occur near Pliocene- (≥400 km) from the trench (Fig. 3B and 3C). trondhjemite-tonalite-dacite (TTD) by partial Quaternary spreading center–trench triple junc- During this transitional stage, lasting several melting of the subducted slab was widespread tions, where very young oceanic lithosphere is million years, adakitic melts are generated during Archean time, and these rocks represent a being or was recently subducted. The remaining across a wide volcanic arc. This corresponds to major component of Precambrian gneiss terranes occurrences involve subduction of moderately modern Ecuador (arc 250–400 km from trench) (Martin, 1986; Drummond and Defant, 1990). old (10–45 Ma) lithosphere, which is not ex- (Monzier et al., 1997; Gutscher et al., 1999b; However, given the cooler mantle temperatures pected to melt under normal subduction-zone Bourdon et al., 1999) and to central Chile at during the Phanerozoic, these processes should pressure and temperature conditions. We present 10–5 Ma (arc 250–800 km from trench) (Kay be uncommon today (Martin, 1986). Recent a new geodynamic model to explain the forma- and Abbruzzi, 1996). Due to the unique set of models of magma genesis emphasize the role of fluids released via dehydration reactions from the Figure 1. Global distribu- subducting plate, thereby causing melting in the 8 tion of flat slab regions 60°N YB overlying mantle wedge (Schmidt and Poli, (labels correspond to 1998). In the past decade, numerous occurrences Table 1) and adakitic mag- AS of Cenozoic adakites (andesitic and dacitic mag- mas (stars). Filled stars Em 7 mas characterized by strong depletion in heavy are modern occurrences, 9 Sh unfilled stars are 1–6 Ma He rare earth elements and high Sr/Y ratios) have old occurrences. Principal 30°N Ha been documented and discussed as possible oceanic plateaus, hotspot 6 tracks, and subducting PK IB examples of slab melting (Fig. 1) (Defant and MP 5 Drummond, 1990; Morris, 1995). These include arcs are shaded gray: Co 4 Hk—Hikurangi Plateau, ER OJ Li Mount St. Helens (Defant and Drummond, 1993) 0° Mh 3 Lo—Louisville Ridge, Mq GC 2 and the recent major eruption of Mount Pinatubo 10 Au—Austral Plateau, Tu— Tu (Prouteau et al., 1999). Tuamotu Plateau, Mq— Nz Marquesas Plateau, Mh— Au Numerical and petrological studies of pressure- 30°S 1 temperature-time (P-T-t) paths in subduction Manihiki Plateau, Li—Line Lo JF Islands, OJ—Ontong Java zones suggest that this process can only occur for Plateau, ER—Euripik Rise, Hk subduction of very young (≤5 Ma) lithosphere PK—Palau-Kyushu Ridge, 150°E 180° 150°W 120°W90°W (Peacock et al., 1994) (Fig. 2A, solid lines). Para- IB—Izu-Bonin Arc, Sh— 55°S Shatsky Rise, MP—Mid- Pacific Mountains, He—Hess Rise, Ha—Hawaiian Chain, Em—Emperor Chain,YB—Yakutat *Current address: GEOMAR, Marine Geodynamics, Block, AS—Alaska Seamounts, Co—Cocos Ridge, GC—Galápagos-Carnegie Ridge, Nz—Nazca Wischhofstrasse 1-3, D-24148, Germany. E-mail: Ridge, JF—Juan-Fernandez Ridge. [email protected]. Geology; June 2000; v. 28; no. 6; p. 535–538; 3 figures; 1 table. 535 varying age of subducting lithosphere (in m.y.) narrow calc-alkaline arc A A Central Chile (20-12 Ma) Ecuador (6 Ma) v = 3 cm/a 0 0 2 τ 300 Moho 300 = 0 MPa 5 Moho 4.0 600 600 wet solidus steep slab 10 900 900 P-T-t paths 10 50 20 20 flat slab 1300 3.0 50 [km] 1300 50 P-T-t paths P (GPa) partial melting in Hb out 100 asthenospheric 2.0 asthenospherewedge asthenosphere Ec 150 1400 1400 1.0 Ga out Am 0 0 100 200 300 [km] 400 500 600 0 200 400 600 800 1000 ° T ( C) broad "adakitic" arc B Central Chile (10-7 Ma) Ecuador (0 Ma) P-T-t paths based on isotherms in Figure 3 0 B 300 300 Moho v = 6 cm/a 600 600 900 25 m.y. old lithosphere 50 900 4.0 1300 melting in "tongue" flat slab [km] 1300 steep slab (points from 100 3.0 (points from wet solidus slab melting Fig. 3B,C) asthenosphere asthenosphere P (GPa) Fig. 3A) Hb out 150 2.0 1400 1400 Ec 1.0 Ga out 0 100 200 300 [km] 400 500 600 Am final pulse of "adakitic" volcanism 0 C Central Chile (6-4 Ma) 0 200 400 600 800 1000 ° 0 T ( C) Moho 300 300 Figure 2. Pressure-temperature (P-T ) meta- 600 Moho 600 900 50 900 morphic reaction diagram showing expected 1300 P-T-t (t = time) paths for varying conditions. [km] 1300 Ec—eclogite, Am—amphibolite, Ga—garnet, 100 slab melting Hb—hornblende. A: P-T-t paths for normal 27° asthenosphere subduction dip (solid lines), with varying litho- spheric ages, and subduction velocity of 150 1400 3 cm/yr, with no shear heating, according to finite difference models (Peacock et al., 1994, 0 100 200 300 [km] 400 500 600 Fig. 8B). P-T-t paths for flat subduction (dashed) transcurrent faulting and/or are calculated using analytical solution for D Central Chile (0 Ma) no active volcanism block fault uplift (Sierras Pampeanas) 0 slab thermal structure (Davies, 1999) beneath Moho 70 km depth.These paths are much flatter and 300 300 Moho intersect slab melting field (shaded) at 700 °C 600 600 50 900 900 and 2.5 GPa for 10–50 Ma subducted litho- 1300 no asthenospheric wedge sphere. B: P-T-t paths for steep (circles) and [km] 1300 flat (diamonds and squares) subduction 100 based on isotherms in Figure 3 sampled every asthenosphere 50 km along slab surface. 150 1400 isotherms and P-T-t paths involved in flat sub- 0 100 200 300 [km] 400 500 600 duction, slab melting can occur (Fig. 2).
Load more

Recommended publications
  • Uplift, Rupture, and Rollback of the Farallon Slab Reflected in Volcanic
    PUBLICATIONS Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE Uplift, rupture, and rollback of the Farallon slab reflected 10.1002/2017JB014517 in volcanic perturbations along the Yellowstone Key Points: adakite hot spot track • Volcanic perturbations in the Cascadia back-arc region are derived from uplift Victor E. Camp1 , Martin E. Ross2, Robert A. Duncan3, and David L. Kimbrough1 and dismemberment of the Farallon slab from ~30 to 20 Ma 1Department of Geological Sciences, San Diego State University, San Diego, California, USA, 2Department of Earth and • Slab uplift and concurrent melting 3 above the Yellowstone plume Environmental Sciences, Northeastern University, Boston, Massachusetts, USA, College of Earth, Ocean, and Atmospheric promoted high-K calc-alkaline Sciences, Oregon State University, Corvallis, Oregon, USA volcanism and adakite generation • Creation of a seismic hole beneath eastern Oregon resulted from thermal Abstract Field, geochemical, and geochronological data show that the southern segment of the ancestral erosion and slab rupture, followed by Cascades arc advanced into the Oregon back-arc region from 30 to 20 Ma. We attribute this event to thermal a period of slab rollback uplift of the Farallon slab by the Yellowstone mantle plume, with heat diffusion, decompression, and the release of volatiles promoting high-K calc-alkaline volcanism throughout the back-arc region. The greatest Supporting Information: • Supporting Information S1 degree of heating is expressed at the surface by a broad ENE-trending zone of adakites and related rocks • Data Set S1 generated by melting of oceanic crust from the Farallon slab. A hiatus in eruptive activity began at ca. • Data Set S2 22–20 Ma but ended abruptly at 16.7 Ma with renewed volcanism from slab rupture occurring in two separate • Data Set S3 regions.
    [Show full text]
  • Experimental Constraints on Adakitic Metasomatism of Mantle Wedge Peridotites Below Patagonia
    O EOL GIC G A D D A E D C E I H C I L E O S F u n 2 d 6 la serena octubre 2015 ada en 19 Experimental constraints on adakitic metasomatism of mantle wedge peridotites below Patagonia Alexandre Corgne * and Manuel Schilling D. Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Chile *Contact email: [email protected] Abstract. We performed a series of high-pressure (1.5 and Quaternary alkali lavas in the back-arc region (e.g. GPa) and high-temperature (1000-1300 ºC) experiments to Stern and Kilian, 1996; Gorring et al., 1997). The back-arc investigate the geochemical imprints of adakitic lavas are hosts of frequent mantle xenoliths, the study of metasomatism on mantle wedge peridotite. Reaction which has contributed to a better understanding of the couples were prepared using a powdered adakite from petrological and geochemical variability of the sub- Cerro Pampa (Argentina) placed next to a fragment of continental lithospheric mantle (e.g. Stern et al., 1990, spinel lherzolite from Pali Aike (Chile). Preliminary results 1999; Gorring and Kay, 2000; Laurora et al., 2001; show that the main changes in phase relations are Bertotto, 2002; Kilian and Stern, 2002; Bjerg et al., 2005, incongruent dissolution of olivine and associated 2009; Schilling et al., 2005; Rivalenti et al., 2004; Ntaflos precipitacion of secondary orthopyroxene, incongruent dissolution of primary spinel and formation of secondary et al., 2007; Wang et al., 2008; Dantas et al. 2009). spinel, as well as precipitation of secondary clinopyroxene and in some instances zoned plagioclase.
    [Show full text]
  • Potassic “Adakite” Magmas and Where They Come From: a Mystery Solved? John Clemens Kingston University (London) Long Xiao China University of Geosciences (Wuhan)
    1 Potassic “adakite” magmas and where they come from: a mystery solved? John Clemens Kingston University (London) Long Xiao China University of Geosciences (Wuhan) 2 3 4 . Adakites are volcanic and intrusive igneous rocks with 55 to 65 wt% SiO2, Al2O3 > 15 wt%, K2O/Na2O typically < 0.6, high La/Yb and Sr/Y ratios and strong depletion in Yb, Y, and HFSE. The name is from Adak island in the Alaskan Aleutians (Aleut “adak” = father). They are typically found in island and continental arc settings. Some believe then to be equivalents of Archæan TTG rocks – hence their importance. Their geochemical and isotopic characteristics suggest an origin by partial melting of mafic crust at pressures high enough to stabilise garnet and eliminate plagioclase. 5 . Adakites that occur in arcs have been interpreted as melts of the down-going slab. Thermal models suggest that slab melting should be restricted to young, hot subduction zones. Atherton and Petford (1993) suggested melting of young lower crustal rocks, in the upper plate, as an alternative to slab melting. There is some direct geological evidence for this alternative in some areas. 6 . Late Mesozoic granitoids in eastern China occur over wide areas, and lack either temporal or spatial association with subduction. Apart from their SiO2 contents, some have all the other geochemical attributes of typical subduction-related adakites, including a lack of Eu anomalies in their REE spectra, except that their K2O/Na2O > 0.95. This is possibly an erroneous attribution as “adakitic”. However this occurrence casts doubt on the assumption of a subduction-related origin for all adakitic magmas.
    [Show full text]
  • Petrogenesis of Cretaceous Adakite-Like Intrusions of the Gangdese Plutonic Belt, Southern Tibet: Implications for Mid-Ocean Ridge Subduction and Crustal Growth
    Lithos 190–191 (2014) 240–263 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Petrogenesis of Cretaceous adakite-like intrusions of the Gangdese Plutonic Belt, southern Tibet: Implications for mid-ocean ridge subduction and crustal growth Yuan-chuan Zheng a,b,⁎, Zeng-qian Hou b, Ying-li Gong c, Wei Liang a,Qing-ZhongSunb,SongZhanga, Qiang Fu a, Ke-Xian Huang a, Qiu-Yun Li a,WeiLia a School of Earth Sciences and Resources, China University of Geosciences, Beijing 100082, PR China b Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China c Laboratory of Department of Thermal Engineering, Tsinghua University, Beijing 100084, PR China article info abstract Article history: We have conducted a whole-rock geochemical, U–Pb zircon geochronological, and in situ zircon Hf–Oisotopic Received 15 August 2013 compositional study of rocks in southern Tibet from the Langxian igneous suite (including a lamprophyre Accepted 16 December 2013 dyke, mafic enclaves, a granodiorite, and a two-mica granite) and the Nuri igneous suite (a quartz–diorite). U– Available online 24 December 2013 Pb zircon dating indicates that the timing of crystallization of the mafic enclaves and host granodiorite of the Langxian suite are ca. 105 Ma and 102 Ma, respectively, that the Langxian lamprophyre dyke and the two- Keywords: – – Geochemistry mica granite were emplaced at ca. 96 Ma and 80 76 Ma, respectively, and that the Nuri quartz diorite was fi U–Pb zircon ages emplaced at ca. 95 Ma. With the exception of the lamprophyre dyke and ma c enclaves in the Langxian area, Zircon Hf–Oisotopes felsic rocks from the Langxian and Nuri igneous suites all show signs of a geochemical affinity with adakite- 18 Adakite-like rocks like rocks.
    [Show full text]
  • Miocene to Late Quaternary Patagonian Basalts (46–478S): Geochronometric and Geochemical Evidence for Slab Tearing Due to Active Spreading Ridge Subduction
    Journal of Volcanology and Geothermal Research 149 (2006) 346–370 www.elsevier.com/locate/jvolgeores Miocene to Late Quaternary Patagonian basalts (46–478S): Geochronometric and geochemical evidence for slab tearing due to active spreading ridge subduction Christe`le Guivel a,*, Diego Morata b, Ewan Pelleter c,d, Felipe Espinoza b, Rene´ C. Maury c, Yves Lagabrielle e, Mireille Polve´ f,g, Herve´ Bellon c, Joseph Cotten c, Mathieu Benoit c, Manuel Sua´rez h, Rita de la Cruz h a UMR 6112 bPlane´tologie et Ge´odynamiqueQ, Universite´ de Nantes, 2 rue de la Houssinie`re, 44322 Nantes, France b Departamento de Geologı´a. Fac. Cs. Fı´sicas y Matema´ticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile c UMR 6538 bDomaines oce´aniquesQ, UBO-IUEM, place Nicolas-Copernic, 29280 Plouzane´, France d CRPG-CNRS UPR A2300, BP 20, 54501 Vandoeuvre-les-Nancy, France e UMR 5573, Dynamique de la Lithosphe`re, Place E. Bataillon, case 60, 34095, Montpellier Cedex 5, France f LMTG-OMP, 14 Avenue E. Belin, 31400 Toulouse, France g IRD-Departamento de Geologia de la Universidad de Chile, Chile h Servicio Nacional de Geologı´a y Minerı´a, Avda. Santa Marı´a 0104, Santiago, Chile Received 18 May 2005; received in revised form 29 August 2005; accepted 14 September 2005 Abstract Miocene to Quaternary large basaltic plateaus occur in the back-arc domain of the Andean chain in Patagonia. They are thought to result from the ascent of subslab asthenospheric magmas through slab windows generated from subducted segments of the South Chile Ridge (SCR). We have investigated three volcanic centres from the Lago General Carrera–Buenos Aires area (46–478S) located above the inferred position of the slab window corresponding to a segment subducted 6 Ma ago.
    [Show full text]
  • Andean Flat-Slab Subduction Through Time
    Andean flat-slab subduction through time VICTOR A. RAMOS & ANDRE´ S FOLGUERA* Laboratorio de Tecto´nica Andina, Universidad de Buenos Aires – CONICET *Corresponding author (e-mail: [email protected]) Abstract: The analysis of magmatic distribution, basin formation, tectonic evolution and structural styles of different segments of the Andes shows that most of the Andes have experienced a stage of flat subduction. Evidence is presented here for a wide range of regions throughout the Andes, including the three present flat-slab segments (Pampean, Peruvian, Bucaramanga), three incipient flat-slab segments (‘Carnegie’, Guan˜acos, ‘Tehuantepec’), three older and no longer active Cenozoic flat-slab segments (Altiplano, Puna, Payenia), and an inferred Palaeozoic flat- slab segment (Early Permian ‘San Rafael’). Based on the present characteristics of the Pampean flat slab, combined with the Peruvian and Bucaramanga segments, a pattern of geological processes can be attributed to slab shallowing and steepening. This pattern permits recognition of other older Cenozoic subhorizontal subduction zones throughout the Andes. Based on crustal thickness, two different settings of slab steepening are proposed. Slab steepening under thick crust leads to dela- mination, basaltic underplating, lower crustal melting, extension and widespread rhyolitic volcan- ism, as seen in the caldera formation and huge ignimbritic fields of the Altiplano and Puna segments. On the other hand, when steepening affects thin crust, extension and extensive within-plate basaltic flows reach the surface, forming large volcanic provinces, such as Payenia in the southern Andes. This last case has very limited crustal melt along the axial part of the Andean roots, which shows incipient delamination.
    [Show full text]
  • Origin of Adakitic Intrusives Generated During Mid-Miocene East^West Extension in Southern Tibet
    Available online at www.sciencedirect.com R Earth and Planetary Science Letters 220 (2004) 139^155 www.elsevier.com/locate/epsl Origin of adakitic intrusives generated during mid-Miocene east^west extension in southern Tibet Z.-Q. Hou a;Ã, Y.-F. Gao b, X.-M. Qu a, Z.-Y. Rui a, X.-X. Mo c a Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, PR China b Shijiazhuang College of Economy, Shijiazhuang, Hebei, PR China c China University of Geosciences, Beijing 100082, PR China Received 19 June 2003; received in revised form 20 October 2003; accepted 23 December 2003 Abstract Adakite is an intermediate to felsic rock with low K, high Al, Na and Sr, and depleted in Y and HREE, usually occurring in arc settings related to subduction of an oceanic slab. Here we report the occurrence of potassic adakites from south Tibet in an orogenic belt produced by the Indo^Asian continent collision. These adakitic intrusives, as a product of Neogene east^west extension, occur in a Miocene Cu-bearing porphyry belt, which developed along the Gangdese arc paralleling the Yarlung^Zangbo suture, but is locally controlled by NS-striking normal faulting systems. Available age data define a duration of magmatism of 10^18 Ma for the adakitic intrusives and related extrusive analogues in south Tibet, which occur in a post-collisional extensional setting. Geochemical data indicate that these adakitic intrusives are shoshonitic and exhibit calc-alkaline composition with high K, and high Sr/Y and La/Y coupled with low Y and HREE, similar to adakites derived from slab melting.
    [Show full text]
  • Petrogenesis of the Early Cretaceous Adakite-Like Porphyries And
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/257553072 Petrogenesis of the Early Cretaceous adakite- like porphyries and associated basaltic andesites in the eastern Jiangnan orogen... Article in Journal of Asian Earth Sciences · November 2012 DOI: 10.1016/j.jseaes.2012.10.017 CITATIONS READS 13 97 5 authors, including: Xiao-Lei Wang Ming Tang Nanjing University Rice University 49 PUBLICATIONS 1,467 CITATIONS 13 PUBLICATIONS 168 CITATIONS SEE PROFILE SEE PROFILE R. M. Gaschnig University of Massachusetts Lowell 34 PUBLICATIONS 293 CITATIONS SEE PROFILE All content following this page was uploaded by Ming Tang on 20 February 2014. The user has requested enhancement of the downloaded file. Journal of Asian Earth Sciences 61 (2012) 243–256 Contents lists available at SciVerse ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes Petrogenesis of the Early Cretaceous adakite-like porphyries and associated basaltic andesites in the eastern Jiangnan orogen, southern China ⇑ Xiao-Lei Wang a, , Xu-Jie Shu a, Xisheng Xu a, Ming Tang a, Richard Gaschnig b a State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, PR China b Department of Geology, University of Maryland, MD 20742, USA article info abstract Article history: Early Cretaceous quartz porphyries are associated with mantle-derived mafic rocks (basaltic andesites) in Received 4 October 2011 the eastern segment of the Neoproterozoic Jiangnan orogen, southern China. Zircons from two quartz Received in revised form 10 October 2012 porphyries yield identical U–Pb ages at 142 ± 1 Ma by the LA–ICP–MS method.
    [Show full text]
  • Tonalite-Dominated Magmatism in the Abitibi Subprovince, Canada, and Significance for Cu-Au Magmatic-Hydrothermal Systems
    minerals Article Tonalite-Dominated Magmatism in the Abitibi Subprovince, Canada, and Significance for Cu-Au Magmatic-Hydrothermal Systems Lucie Mathieu 1,* , Alexandre Crépon 1 and Daniel J. Kontak 2 1 Centre D’études sur les Ressources Minérales (CERM), Département des Sciences Appliquées, Université du Québec à Chicoutimi (UQAC), 555 blvd. de l’université, Chicoutimi, QC G7H 2B1, Canada; [email protected] 2 Mineral Exploration Research Centre, Harquail School of Earth Sciences, Goodman School of Mines, Laurentian University, 935 Ramsey Lake Road, Sudbury, ON P3E 2C6, Canada; [email protected] * Correspondence: [email protected]; Tel.: +1-418-545-5011 (ext. 2538) Received: 8 February 2020; Accepted: 3 March 2020; Published: 7 March 2020 Abstract: In Archean greenstone belts, magmatism is dominated by intrusive and volcanic rocks with tholeiitic affinities, as well as tonalite- and granodiorite-dominated large-volume batholiths, i.e., tonalite–trondhjemite–granodiorite (TTG) suites. These intrusions are associated with poorly documented mineralization (Cu-Au porphyries) that, in the Neoarchean Abitibi Subprovince (>2.79 to ~2.65 Ga), Superior Province, Canada, are associated with diorite bearing plutons, i.e., tonalite–trondhjemite–diorite (TTD) suites. The importance of TTG versus TTD suites in the evolution of greenstone belts and of their magmatic-hydrothermal systems and related mineralization is unconstrained. The aim of this study was to portray the chemistry and distribution of these suites in the Abitibi Subprovince. The study used data compiled by the geological surveys of Québec and Ontario to evaluate the chemistry of TTG and TTD suites and uncovered two coeval magmas that significantly differentiated (fractional crystallization mostly): 1) a heavy rare earth elements (HREE)-depleted tonalitic magma from high pressure melting of an hydrated basalt source; and 2) a hybrid HREE-undepleted magma that may be a mixture of mantle-derived (tholeiite) and tonalitic melts.
    [Show full text]
  • A New Magma Type in the Continental Collision Zone. the Case of Capraia Island (Tuscany, Italy)
    geosciences Article A New Magma Type in the Continental Collision Zone. The Case of Capraia Island (Tuscany, Italy) Alba Patrizia Santo Department of Earth Sciences, University of Florence, Via A. La Pira 4, 50121 Florence, Italy; alba.santo@unifi.it Abstract: The Tuscany Magmatic Province consists of a Miocene to Pleistocene association of a wide variety of rock types, including peraluminous crustal anatectic granites and rhyolites, calcalkaline and shoshonitic suites and ultrapotassic lamproites. In addition to the magma types already recognised, the occurrence of a new, distinct magma type at Capraia and Elba islands and in mafic enclaves in the San Vincenzo rhyolites has been suggested by recent studies. This particular type of magma, represented by intermediate to acidic calcalkaline rocks showing high Sr, Ba, and LREE, is restricted to the northwestern sector of the province and to a time interval of about 8 to 4.5 Ma. New data obtained on rocks from Capraia Island have allowed for the verification of the occurrence of this new magma type, the exploration of its origin and a discussion of its possible geodynamic significance. The high-Sr-Ba andesite-dacite rocks occurring in the Laghetto area at Capraia display a composition that is intermediate between adakitic and calcalkaline rocks. It is suggested that they represent a distinct type of magma that originated at mantle pressure by melting of the lower continental crust, followed by mixing with other Capraia magmas. The geodynamic model that best explains the composition of the studied rocks is the thickening of the continental crust during continental collision, followed by extension that favoured melting of the lower crust.
    [Show full text]
  • Slab-Tearing Following Ridge-Trench Collision: Evidence from Miocene Volcanism in Baja California, México ⁎ Carlos Pallares A, , René C
    Journal of Volcanology and Geothermal Research 161 (2007) 95–117 www.elsevier.com/locate/jvolgeores Slab-tearing following ridge-trench collision: Evidence from Miocene volcanism in Baja California, México ⁎ Carlos Pallares a, , René C. Maury a, Hervé Bellon b, Jean-Yves Royer a, Thierry Calmus c, Alfredo Aguillón-Robles d, Joseph Cotten b, Mathieu Benoit a, François Michaud e, Jacques Bourgois f a UMR 6538, Domaines Océaniques, IUEM, Université de Bretagne Occidentale, Place Nicolas Copernic, F-29280 Plouzané, France b UMR 6538, Domaines Océaniques, IUEM, Université de Bretagne Occidentale, 6, Av. Le Gorgeu, C.S. 93837, F-29238 Brest Cedex 3, France c Estación Regional del Noroeste, Instituto de Geología, UNAM, Hermosillo, Son., C.P. 83000, México d Instituto de Geología, UASLP, Av. Dr. Manuel Nava no. 5, Zona Universitaria, San Luis Potosí, S.L.P., C.P. 78250, México e UMR 6526, Géosciences Azur, Université Pierre et Marie Curie, F-06235 Villefranche sur Mer, France f IRD and CNRS, UMR 6526, Escuela Politecnica Nacional (EPN), Departamento de Geología y Riesgos Naturales (DGRN), Andalucia n/s, P.O. Box 17-01-2759, Quito, Ecuador Received 15 June 2006; received in revised form 3 November 2006; accepted 12 November 2006 Available online 5 January 2007 Abstract Neogene magmatic activity in Central Baja California underwent a major change at ca. 12.5 Ma, when the Pacific–Farallon active oceanic ridge collided with the trench east of Vizcaíno Peninsula. The calc-alkaline magmatism which built the Comondú volcanic arc vanished and was replaced by unusual volcanic associations, which were erupted within six Late Miocene to Quaternary volcanic fields (Jaraguay, San Borja, San Ignacio, Santa Rosalía, Santa Clara, La Purísima), delineating a 600 km array along the Baja California Peninsula.
    [Show full text]
  • The Generation and Evolution of Archean Continental Crust in The
    Precambrian Research 235 (2013) 251–263 Contents lists available at SciVerse ScienceDirect Precambrian Research jou rnal homepage: www.elsevier.com/locate/precamres The generation and evolution of Archean continental crust in the Dunhuang block, northeastern Tarim craton, northwestern China a,∗ a b b a Keqing Zong , Yongsheng Liu , Zeming Zhang , Zhenyu He , Zhaochu Hu , a a Jingliang Guo , Kang Chen a State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China b Institute of Geology, Chinese Academy of Geological Sciences, No. 26, Baiwanzhuang Road, Beijing 100037, China a r t i c l e i n f o a b s t r a c t Article history: Tonalite–trondhjemite–granodiorite (TTG) preserved in Archean cratons can provide insights into the Received 3 March 2013 generation and evolution of the early continental crust. In this study, typical TTG gneisses from the Dun- Received in revised form 29 June 2013 huang block in the northeastern Tarim craton were studied in detail regarding their geochemistry and Accepted 2 July 2013 geochronology to constrain the generation and evolution of the Archean continental crust in this region. Available online xxx These TTG gneisses are characterized by high contents of SiO2 (68.3–71.6%), Al2O3 (15.3–16.9%), Na2O (4.43–4.85%), low K2O/Na2O ratios (0.20–0.37) and a very low HREE content (Yb < 1 ppm) and show two- Keywords: stage Nd isotope model ages of ∼3.06–2.84 Ga. Zircon U–Pb analyses reveal that these TTG gneisses were TTG ∼ Archean formed 2.7–2.6 Ga ago, as shown by inherited magmatic zircon cores, and were later altered by Paleo- proterozoic (∼2.0–1.9 Ga) and early Paleozoic (∼430 Ma) high-grade metamorphic events.
    [Show full text]