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Yoshiyuki Tatsumi - One of the best experts on this subject based on the ideXlab platform.
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high mg andesites in the setouchi Volcanic Belt southwestern japan analogy to archean magmatism and continental crust formation
Annual Review of Earth and Planetary Sciences, 2006Co-Authors: Yoshiyuki TatsumiAbstract:AbstractThe occurrence of unusual high-Mg andesite (HMA) characterizes the Setouchi Volcanic Belt in SW Japan, which was activated at 13.7±1.0 Ma by subduction of the young and hot Shikoku Basin lithosphere into the high-temperature upper mantle. This tectonic setting may be analogous to the thermal regime during Archean times, which suggests more ubiquitous production of HMA. A plausible process that can comprehensively account for the petrological and geochemical characteristics of Setouchi HMAs involves partial melting of subducting lithosphere, subsequent melt-mantle interactions, and final equilibration with the upper-most mantle. HMAs and more differentiated andesites, which are coined sanukitoids, are distinct in that they are phenocryst-poor (<10%), compact, and nearly anhydrous, despite HMA magmas originally containing ∼7 wt% H2O, and commonly form composite lava flows. One mechanism for explaining these features is formation of a mostly solidified HMA pluton, remelting of the HMA pluton by intru...
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geochemical modeling of dehydration and partial melting of subducting lithosphere toward a comprehensive understanding of high mg andesite formation in the setouchi Volcanic Belt sw japan
Geochemistry Geophysics Geosystems, 2003Co-Authors: Yoshiyuki Tatsumi, Takeshi HanyuAbstract:[1] Possible mechanisms for the production of mantle-derived, high-Mg andesite magmas, including (1) partial melting of mantle wedge peridotite by addition of aqueous fluids from the subducting lithosphere and (2) partial melting of the subducting sediments and altered oceanic crust, and subsequent melt-mantle interaction, were examined by geochemical formulation of dehydration, partial melting and melt-solid reactions. The modeling results demonstrate that both mechanisms can reasonably explain the incompatible trace element characteristics of high-Mg andesites in the Setouchi Volcanic Belt, SW Japan. However, simple hydrous melting of mantle wedge peridotite cannot account for the Sr-Nd-Pb-Hf isotopic compositions of such andesites. By contrast, the latter mechanism, which is consistent with thermal structures beneath the Setouchi Volcanic Belt, can well reproduce the isotopic signature of those high-Mg andesites.
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geochemical modeling of partial melting of subducting sediments and subsequent melt mantle interaction generation of high mg andesites in the setouchi Volcanic Belt southwest japan
Geology, 2001Co-Authors: Yoshiyuki TatsumiAbstract:A possible mechanism for high-Mg andesite formation, including melting of subducting sediments and subsequent melt-mantle interaction, was examined by geochemical formulation of partial melting and melt-solid reactions. The modeling results demonstrate that a sediment-derived melt produced at 1050 °C and 1.0 GPa changes its composition from rhyolitic to andesitic as it dissolves olivine and clinopyroxene and crystallizes orthopyroxene. The resulting reaction product possesses major and incompatible trace element compositions close to high-Mg andesites in the Setouchi Volcanic Belt, southwest Japan.
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tectonic setting of high mg andesite magmatism in the sw japan arc k ar chronology of the setouchi Volcanic Belt
Geophysical Journal International, 2001Co-Authors: Yoshiyuki Tatsumi, Kyoichi Ishizaka, Naoto Ishikawa, Ken Anno, Tetsumaru ItayaAbstract:Summary The Setouchi Volcanic Belt in SW Japan is characterized by the occurrence of andesites with an unusually high Mg concentration (high-Mg andesites, HMAs). Such HMAs may have formed under unusual tectonic settings, as basaltic magmas are produced dominantly in the mantle wedge of modern subduction zones. A total of 50 new K–Ar ages for the Setouchi rocks confirmed that intermediate to felsic magmatism including the eruption of HMAs took place in this Volcanic Belt within a short period of 13.2 ± 0.4 Ma. This is synchronous with the clockwise rotation of the SW Japan arc sliver that was associated with the opening of the Japan Sea back-arc basin. Such rotation of an arc sliver forced the initiation of subduction and partial melting of a young and hot lithosphere of the Shikoku Basin beneath the arc. Interaction between slab melts and mantle wedge peridotites may be a possible generation process of unusual HMA magmas. When the SW Japan arc sliver ceased to drift, the Setouchi magmatism was switched off by the cessation of subduction. The eruption of HMA magmas may also be attributed to an extensional stress field in the Setouchi region, in contrast to the compressional stress regime documented for other regions of the SW Japan arc.
Susanne M Straub - One of the best experts on this subject based on the ideXlab platform.
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geochemical and petrological insights into the tectonic origin of the transmexican Volcanic Belt
Earth-Science Reviews, 2016Co-Authors: Arturo Gomeztuena, Laura Mori, Susanne M StraubAbstract:Abstract The Transmexican Volcanic Belt (TMVB) is the magmatic expression of one of the most complex convergent margins on the planet, and as such constitutes a prime location for testing emerging hypotheses on arc magma genesis and its influence on continental crust formation. By coupling an extensive geochemical and petrological database with an improved stratigraphic and geophysical framework, in this contribution we will examine the compositional diversity of the TMVB from the perspective of changes in subduction zone geometry and crustal thickness, as well as within the context of more subtle tectonic processes such as lithospheric foundering, slab detachment, fore-arc subduction erosion, crustal relamination and diapiric exhumation. We will illustrate that the compositional variability of mafic magmas across the region is an inherited characteristic of a geochemically enriched pre-subduction background mantle wedge, which has been variably overprinted by diverse chemical fluxes released from the slab at different thermal conditions. We will argue that the volumetrically dominant intermediate magmas in Mexico — from andesite to dacite and even some rhyolite — represent primary melts from hybrid slab and mantle sources, with no perceptible compositional influences from the overlying continental crust. These interpretations depart from conventional models that invoke intra-crustal differentiation and contamination of basalt to create intermediate magmas, and therefore have important implications to understanding the genesis of global continents.
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Crustal recycling by subduction erosion in the central Mexican Volcanic Belt
Geochimica et Cosmochimica Acta, 2015Co-Authors: Susanne M Straub, Arturo Gómez-tuena, Ilya N. Bindeman, Louise L. Bolge, Philipp A. Brandl, Ramon Espinasa-perena, Luigi Solari, Finlay M. Stuart, Paola Vannucchi, Georg F. ZellmerAbstract:Recycling of upper plate crust in subduction zones, or ‘subduction erosion’, is a major mechanism of crustal destruction at convergent margins. However, assessing the impact of eroded crust on arc magmas is difficult owing to the compositional similarity between the eroded crust, trench sediment and arc crustal basement that may all contribute to arc magma formation. Here we compare Sr–Nd–Pb–Hf and trace element data of crustal input material to Sr–Nd–Pb–Hf–He–O isotope chemistry of a well-characterized series of olivine-phyric, high-Mg# basalts to dacites in the central Mexican Volcanic Belt (MVB). Basaltic to andesitic magmas crystallize high-Ni olivines that have high mantle-like 3He/4He = 7–8 Ra and high crustal δ18Omelt = +6.3–8.5‰ implying their host magmas to be near-primary melts from a mantle infiltrated by slab-derived crustal components. Remarkably, their Hf–Nd isotope and Nd/Hf trace element systematics rule out the trench sediment as the recycled crust end member, and imply that the coastal and offshore granodiorites are the dominant recycled crust component. Sr–Nd–Pb–Hf isotope modeling shows that the granodiorites control the highly to moderately incompatible elements in the calc-alkaline arc magmas, together with lesser additions of Pb- and Sr-rich fluids from subducted mid-oceanic ridge basalt (MORB)-type altered oceanic crust (AOC). Nd–Hf mass balance suggests that the granodiorite exceeds the flux of the trench sediment by at least 9–10 times, corresponding to a flux of ⩾79–88 km3/km/Myr into the subduction zone. At an estimated thickness of 1500–1700 m, the granodiorite may buoyantly rise as bulk ‘slab diapirs’ into the mantle melt region and impose its trace element signature (e.g., Th/La, Nb/Ta) on the prevalent calc-alkaline arc magmas. Deep slab melting and local recycling of other slab components such as oceanic seamounts further diversify the MVB magmas by producing rare, strongly fractionated high-La magmas and a minor population of high-Nb magmas, respectively. Overall, the central MVB magmas inherit their striking geochemical diversity principally from the slab, thus emphasizing the importance of continental crust recycling in modern solid Earth relative to its new formation in modern subduction zones.
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the processes of melt differentiation in arc Volcanic rocks insights from oib type arc magmas in the central mexican Volcanic Belt
Journal of Petrology, 2013Co-Authors: Susanne M Straub, Ana Lillian Martindel Pozzo, Arturo Gomeztuena, Charles H Langmuir, Finlay M. Stuart, Georg F. Zellmer, Ramon Espinasaperena, Gary T MeskoAbstract:Andesite petrogenesis is inextricably linked to plate processing at convergent margins. The details of andesite formation, however, remain poorly understood because the signatures of the initial arc mantle melts are often modified in the overlying crust. To distinguish initial mantle from crustal signatures in arc magmas, we studied two compositionally zoned Holocene monogenetic volcanoes, Texcal Flow and Volcan Chichinautzin, in the central Mexican Volcanic Belt (MVB). Texcal Flow and V. Chichinautzin erupt ‘ocean island basalt (OIB)-type’, high-Nb (17–36 ppm), olivine-phyric basalts to basaltic andesites (49·4–57·3 wt % SiO2; Mg# = 68–50) that show an arc affinity in their major element oxides. At both volcanoes melt SiO2 increases with time. However, systematic changes of melt SiO2 with 87Sr/86Sr and 143Nd/144Nd, the overall low 87Sr/86Sr = 0·70305–0·70453 and high 143Nd/144Nd = 0·51273–0·51299 relative to continental crust, and the high 3He/4He = 7–8 Ra of olivine phenocrysts preclude melt silica enrichment by crustal assimilation and fractional crystallization. Instead, the data require the existence of silicic initial mantle melts. The high Ni abundances of olivines suggest that the silicic melts originate from segregations of ‘reaction pyroxenites’ that formed in the peridotite mantle wedge following multiple infiltrations of silicic slab components. Sequential melting of zoned silica-deficient to silica-excess pyroxenites can reproduce the time-progressive evolution of melt silica content at Texcal Flow and V. Chichinautzin. As initial melts always have high Mg# > 70 regardless of their SiO2 content, the low-Mg# values of the magmas erupted must reflect loss of moderate amounts (<15%) of olivine and possibly pyroxenes at crustal levels. Fractional crystallization and recharge mixing nearly erase all mantle signatures in the most silicic V. Chichinautzin magmas, so that their origin can only be inferred from their association with the more mafic precursory melts. The pyroxenite model implies that ∼15–18 wt % of the erupted melt mass, and possibly more, is slab-derived. We infer that the elements Fe, Mg, Ca and Ti are principally mantle-derived, whereas significant amounts of the elements Si, K, Na, P and possibly Al may be contributed from slab. As blends of mantle and slab materials, the OIB-type Texcal Flow and V. Chichinautzin magmas provide limited indication of the composition of the sub-arc mantle prior to subduction modification, which is inferred to be similar to primitive mantle, but less enriched than the sources of the intraplate magmas behind the MVB Volcanic front.
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evidence from high ni olivines for a hybridized peridotite pyroxenite source for orogenic andesites from the central mexican Volcanic Belt
Geochemistry Geophysics Geosystems, 2008Co-Authors: Susanne M Straub, A Lagatta, Ana Lillian Martindel Pozzo, Charles H LangmuirAbstract:[1] Subduction zone magmatism produces calc-alkaline andesite melts that combine the high SiO2, Na2O, and K2O abundances of the differentiated continental crust with low FeO, FeO/MgO, and TiO2 typical of melts from depleted mantle. Ni-rich olivines in basaltic andesites and andesites of the central Mexican Volcanic Belt suggest that this dichotomy reflects a particular mechanism of mantle processing in the subduction environment. Hydrous slab components rich in Si, Na, and fluid mobile large-ion lithophile elements (LILE) transform mantle olivine to “reaction orthopyroxene.” Along the ascent paths, and embedded into surrounding peridotite, secondary pyroxenite lithologies are created that are composed of “reaction orthopyroxene” next to mantle clinopyroxene and orthopyroxene. Partial melts from peridotite and pyroxenite then mix to produce primary calc-alkaline basaltic andesites and andesites that are rich in Na and LILE. The steady slab flux maintains high levels of Na and LILE in the mantle source but also induces repetitive melting that steadily depletes the subarc mantle in FeO, TiO2, and other high field strength elements. If mantle processing thus creates primary basaltic andesite and andesite melts with the fractionated major element signature of the continental crust, the high magnesium number (Mg # (=Mg/Mg + Fe2+)) ∼60–70 of these melts still requires additional differentiation to arrive at the lower Mg # ∼55 of average continental crust.
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geochemical evidence for slab melting in the trans mexican Volcanic Belt
Journal of Petrology, 2006Co-Authors: Arturo Gomeztuena, Susanne M Straub, Charles H Langmuir, Steven L. Goldstein, Fernando OrtegagutierrezAbstract:Geochemical studies of Plio-Quaternary Volcanic rocks from theValle de Bravo^Zita¤ cuaro Volcanic field (VBZ) in central Mexico indicate that slab melting plays a key role in the petrogenesis of theTransMexican Volcanic Belt. Rocks from the VBZ are typical arc-related high-Mg andesites, but two different rock suites with distinct trace element patterns and isotopic compositions erupted concurrently in the area, with a trace element character that is also distinct from that of other Mexican volcanoes. The geochemical differences between the VBZ suites cannot be explained by simple crystal fractionation and/or crustal assimilation of a common primitive magma, but can be reconciled by the participation of different proportions of melts derived from the subducted basalt and sediments interacting with the mantle wedge. Sr/Yand Sr/Pb ratios of theVBZ rocks correlate inversely with Pb and Sr isotopic compositions, indicating that the Sr and Pb budgets are strongly controlled by melt additions from the subducted slab. In contrast, an inverse correlation between Pb(Th)/Nd and Nd/Nd ratios, which extend to lower isotopic values than those for Pacific mid-ocean ridge basalts, indicates the participation of an enriched mantle wedge that is similar to the source of Mexican intraplate basalts. In addition, a systematic decrease in middle and heavy rare earth concentrations and Nb/Ta ratios with increasing SiO2 contents in theVBZ rocks is best explained if these elements are mobilized to some extent in the subduction flux, and suggests that slab partial fusion occurred under garnet amphibolite-facies conditions.
Max Suter - One of the best experts on this subject based on the ideXlab platform.
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the 2 october 1847 mi 5 7 chapala graben triggered earthquake trans mexican Volcanic Belt west central mexico macroseismic observations and hazard implications
Seismological Research Letters, 2018Co-Authors: Max SuterAbstract:ABSTRACT The Trans‐Mexican Volcanic Belt is an active continental Volcanic arc related to subduction along the Middle America trench and characterized by several major arc‐parallel middle Miocene—Holocene lake basins formed by normal faults and related crustal seismicity. The Chapala graben, the largest of these basins in the western part of the Trans‐Mexican Volcanic Belt, is 115 km long and up to 30 km wide. Here, I document a 2 October 1847 earthquake with intensity magnitude M I of 5.7±0.4 that was locally devastating on the northern graben shoulder. It razed the villages of Poncitlan and Ocotlan in the state of Jalisco, where at least 58 persons perished. The macroseismic observations for this historical event and the elevated background seismicity indicate that the Chapala graben is active and poses a major ground‐shaking hazard to the nearby metropolitan areas of Ocotlan and Guadalajara. No historical earthquake had been previously documented from the Chapala graben, which was believed to be tectonically inactive. Furthermore, the 2 October 1847 event was not recognized as a crustal earthquake. In earthquake catalogs, the devastation at Ocotlan is aggregated with the damage caused on the same day, only two hours earlier, in the Colima region by a subduction‐zone earthquake that was devastating in Tecoman and Colima and caused minor damage in Mexico City, and which likely triggered dynamically the Chapala graben earthquake.
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the a d 1567 mw 7 2 ameca jalisco earthquake western trans mexican Volcanic Belt surface rupture parameters seismogeological effects and macroseismic intensities from historical sources
Bulletin of the Seismological Society of America, 2015Co-Authors: Max SuterAbstract:The A.D. 1567 Ameca, Jalisco, earthquake (west‐central Mexico) is the strongest known historical crustal earthquake in the Trans‐Mexican Volcanic Belt, an active Volcanic arc being deformed by an intra‐arc extensional fault network. The location of the surface rupture at the base of the Sierra de Ameca mountain range, its length (13–14 leagues, 54–59 km) and the scarp height (1–2 estados , 1.67–3.34 m) are inferred from the description of this earthquake in the Relacion de Ameca of 1579, which contains what is probably the earliest documentation of an earthquake surface rupture in the Americas. From scaling relations, the moment magnitude of this earthquake can be estimated as 7.2±0.3, based on the rupture length. The A.D. 1567 Ameca earthquake is likely to have ruptured to the surface along two (or all three) major segments of the Ameca–San Marcos normal fault system. Online Material: Excerpts from five historical documents related to the 1567 Ameca earthquake.
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quaternary intra arc extension in the central trans mexican Volcanic Belt
Geological Society of America Bulletin, 2001Co-Authors: Max Suter, Margarita Lopez Martinez, Odranoel Quintero Legorreta, Miguel Carrillo MartinezAbstract:The Trans-Mexican Volcanic Belt is an active Volcanic arc related to subduction along the Middle America trench and characterized by shallow seismicity and synVolcanic to postVolcanic extensional arc-parallel faulting. Major intra-arc basins within the central part of the Belt (between long 998W and 1028W) are (from west to east) the Cuitzeo and Acambay grabens, the Aljibes half-graben, and the Mezquital graben. In this region, ;100 eastwest2striking, .2 km long, steeply dipping normal faults, expressed by pronounced multi-event fault scarps, have been mapped. Of the 100 faults, ;65 displace rocks of known Quaternary age (younger than 1.6 Ma), and 22 cut rocks with a documented age younger than 750 ka. Known historical surface ruptures are limited to faults of the Acambay graben. Overall, the faults cause north-south to north-northwest2south-southeast2oriented extension of ,1 km, which is distributed over a 30250-km-wide zone that has 5210 faults in cross section and a relative extension of ,3%. Quaternary vertical slip rates, estimated for 13 of the faults, have a mean of 0.07 mm/yr. They are highest at the southern margin of the Cuitzeo graben, the northern margin of the Acambay graben, and in the Aljibes half-graben, where they measure between 0.16 and 0.18 mm/yr. The north-south to north-northwest2south-southeast2oriented Quaternary bulk extension rate of the system is likely to be 0.2 6 0.05 mm/yr. This fault system is in an initial stage of coalescence. Its western and eastern parts consist mostly of isolated fault segments, whereas in the central part deformation is localized onto a few through-going faults. The longest of these are the Venta de Bravo fault (45 km) and the Acambay-Tixmadeje fault (34 km). The short fault traces have a simple structure, whereas the longer ones are commonly composed of two or more segments. There is no obvious migratory pattern of Quaternary fault activity, which suggests that the entire region is tectonically active.
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the acambay graben active intraarc extension in the trans mexican Volcanic Belt mexico
Tectonics, 1995Co-Authors: Max Suter, Gerardo J Aguirrediaz, Odranoel Quinterolegorreta, Margarita Lopezmartinez, Edward FarrarAbstract:The trans-Mexican Volcanic Belt is an active Volcanic arc related to subduction along the Middle America trench. The central part of the Belt is being deformed by the Chapala-Tula fault zone, an approximately 450-km-long and 50-km-wide zone of active extension. The Volcanic arc and the arc-parallel Chapala-Tula fault zone are superposed nearly perpendicularly on the preexisting stress and deformation province of the Mexican Basin and Range. The Acambay graben, about 40 km long and 15 km wide, is located approximately 100 km northwest of Mexico City and is one of the major troughs within the Chapala-Tula fault zone. The border faults of the Acambay graben, Acambay-Tixmadeje in the north and Pastores in the south, are separated in the west by stepovers from range-bounding faults of similar orientation, Epitacio Huerta in the north and Venta de Bravo in the south. The stepovers occur at the intersection of these faults with an older system of Basin and Range faults. An early-stage right-lateral component of motion along the Venta de Bravo and Pastores faults is inferred on a map scale from a left-stepping en echelon array of normal fault segments. The divergence of the en echelon segments from the general fault trend decreases gradually from west to east, suggesting that the early extension was rotational. The present relative displacement along the southern margin of the system, on the other hand, results in a left-lateral strike-slip component. This is documented on a map scale from extension structures at left stepovers and on an outcrop scale from fault striations indicating left-oblique slip. The striations measured at the northern system margin indicate nearly pure extensional dip slip without a consistent lateral displacement component. This is supported on a map scale by the structure of the right stepover between the Acambay-Tixmadeje and Epitacio Huerta faults, which shows no evidence of local extension or shortening. The divergence between the present directions of motion at the southern and northern margins of the extended zone can be explained by a minor rotational deformation component with the pole of rotation being located to the east of the zone of deformation. This could explain why no active extension has been observed to the east of the Chapala-Tula fault zone, in the eastern part of the trans-Mexican Volcanic Belt. During the Ms = 6.9 Acambay earthquake of November 19, 1912, surface rupture occurred along both margins of the graben at the base of multiple-event scarps. Along the Acambay-Tixmadeje fault, the coseismic rupture is 41 km long. The vertical offset increases gradually from the eastern end of the surface rupture to its center where it is with 50 cm at a maximum. Furthermore, the change in the vertical surface offset along the fault is approximately proportional to the change in height of the Acambay-Tixmadeje multiple-event fault scarp. The easternmost part of the ground rupture passes through a plain and not at the base of a multiple-event scarp as farther west. It may therefore correspond partly to an increase in length of the Acambay-Tixmadeje fault during the 1912 earthquake. The slip rate along the southern border of the Acambay graben can be estimated from the displacement and age of a basalt flow for which we have obtained a 40Ar/39Ar age of 0.4±0.1 Ma. This basalt may be displaced up to 15 m by the Pastores fault, which indicates a middle-late Quaternary slip rate of ≤0.04 mm/yr. Furthermore, based on a coseismic surface rupture of approximately 20 cm along this fault in the 1912 earthquake, we estimate a recurrence interval of ≥5000 years for major earthquakes along the faults of the Acambay graben.
Arturo Gomeztuena - One of the best experts on this subject based on the ideXlab platform.
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geochemical and petrological insights into the tectonic origin of the transmexican Volcanic Belt
Earth-Science Reviews, 2016Co-Authors: Arturo Gomeztuena, Laura Mori, Susanne M StraubAbstract:Abstract The Transmexican Volcanic Belt (TMVB) is the magmatic expression of one of the most complex convergent margins on the planet, and as such constitutes a prime location for testing emerging hypotheses on arc magma genesis and its influence on continental crust formation. By coupling an extensive geochemical and petrological database with an improved stratigraphic and geophysical framework, in this contribution we will examine the compositional diversity of the TMVB from the perspective of changes in subduction zone geometry and crustal thickness, as well as within the context of more subtle tectonic processes such as lithospheric foundering, slab detachment, fore-arc subduction erosion, crustal relamination and diapiric exhumation. We will illustrate that the compositional variability of mafic magmas across the region is an inherited characteristic of a geochemically enriched pre-subduction background mantle wedge, which has been variably overprinted by diverse chemical fluxes released from the slab at different thermal conditions. We will argue that the volumetrically dominant intermediate magmas in Mexico — from andesite to dacite and even some rhyolite — represent primary melts from hybrid slab and mantle sources, with no perceptible compositional influences from the overlying continental crust. These interpretations depart from conventional models that invoke intra-crustal differentiation and contamination of basalt to create intermediate magmas, and therefore have important implications to understanding the genesis of global continents.
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hafnium isotope evidence for slab melt contributions in the central mexican Volcanic Belt and implications for slab melting in hot and cold slab arcs
Chemical Geology, 2014Co-Authors: A Lagatta, Ana Lillian Martindel Pozzo, Arturo Gomeztuena, Charles H Langmuir, Steven L. Goldstein, Yue Cai, Gerardo CarrasconunezAbstract:This study presents evidence that Quaternary frontal arc calc-alkaline lavas from Central Mexican Volcanic Belt (CMVB) contain contributions from partial melts of the subducting garnet-bearing eclogitic oceanic crust and sediment, based on chemical and Hf–Nd isotope data. The CMVB includes both calc-alkaline lavas with arc-type trace element patterns such as aqueous fluid mobile element enrichments and high field strength element depletions; and “high-Nb” alkaline lavas with trace element patterns similar to ocean island basalts. The two types of lavas are closely related geographically and temporally. Distinct from the high-Nb lavas, the calc-alkaline lavas show trends toward higher 176Hf/177Hf and 143Nd/144Nd ratios coupled with lower Lu/Hf. The high Hf–Nd isotope ratios fingerprint contributions of subducted basaltic ocean crust, while the correlation with low Lu/Hf indicates melting in the presence of residual garnet, which reflects conversion of the subducted oceanic crust to eclogite. Isotopic and chemical mass balance considerations indicate that the slab melts are ~ 80% basaltic oceanic crust and ~ 20% subducted sediment. The calc-alkaline lavas have higher SiO2 at a given Mg# compared to the high-Nb alkaline lavas, also reflecting melt contributions from the subducted slab. A survey of global arc lavas shows that calc-alkaline lavas with low Lu/Hf ratios, reflecting melting in the presence of residual garnet and preferential mobilization of Hf over Lu from the subducted slab, are generally associated with hot slab conditions. These include arcs where young (< 30 Ma old) ocean crust is subducted (e.g. Mexican Volcanic Belt, Cascades, Austral Andes, Luzon, Setouchi), where slab tearing occurred and hot asthenospheric mantle could upwell through the slab window (e.g., western Aleutians, Sunda, southern Scotia), and where oblique or slow subduction leads to higher slab temperatures (e.g. Lesser Antilles, western Aleutians). In some of these hot slab arcs, where low Lu/Hf ratios are coupled with high Nd–Hf isotope ratios, slab melt contributions are dominated by partial melts from the subducted oceanic basalt (e.g., Mexican Volcanic Belt, Aleutians and Cascades). In other hot slab arcs, low Lu/Hf ratios are coupled with low Nd–Hf isotope ratios, reflecting slab contributions dominated by sediment melts (e.g. Setouchi, Lesser Antilles, Luzon, Sunda, and southern Scotia). Arcs associated with colder subducted oceanic crust (e.g. Izu–Bonin–Marianas, Tonga–Kermadec, central and northern Scotia) erupt lavas with high Lu/Hf along with high Hf–Nd isotope ratios, similar to mid-ocean ridge basalts, thus they lack the signature of residual garnet as well as significant slab melt input.
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the processes of melt differentiation in arc Volcanic rocks insights from oib type arc magmas in the central mexican Volcanic Belt
Journal of Petrology, 2013Co-Authors: Susanne M Straub, Ana Lillian Martindel Pozzo, Arturo Gomeztuena, Charles H Langmuir, Finlay M. Stuart, Georg F. Zellmer, Ramon Espinasaperena, Gary T MeskoAbstract:Andesite petrogenesis is inextricably linked to plate processing at convergent margins. The details of andesite formation, however, remain poorly understood because the signatures of the initial arc mantle melts are often modified in the overlying crust. To distinguish initial mantle from crustal signatures in arc magmas, we studied two compositionally zoned Holocene monogenetic volcanoes, Texcal Flow and Volcan Chichinautzin, in the central Mexican Volcanic Belt (MVB). Texcal Flow and V. Chichinautzin erupt ‘ocean island basalt (OIB)-type’, high-Nb (17–36 ppm), olivine-phyric basalts to basaltic andesites (49·4–57·3 wt % SiO2; Mg# = 68–50) that show an arc affinity in their major element oxides. At both volcanoes melt SiO2 increases with time. However, systematic changes of melt SiO2 with 87Sr/86Sr and 143Nd/144Nd, the overall low 87Sr/86Sr = 0·70305–0·70453 and high 143Nd/144Nd = 0·51273–0·51299 relative to continental crust, and the high 3He/4He = 7–8 Ra of olivine phenocrysts preclude melt silica enrichment by crustal assimilation and fractional crystallization. Instead, the data require the existence of silicic initial mantle melts. The high Ni abundances of olivines suggest that the silicic melts originate from segregations of ‘reaction pyroxenites’ that formed in the peridotite mantle wedge following multiple infiltrations of silicic slab components. Sequential melting of zoned silica-deficient to silica-excess pyroxenites can reproduce the time-progressive evolution of melt silica content at Texcal Flow and V. Chichinautzin. As initial melts always have high Mg# > 70 regardless of their SiO2 content, the low-Mg# values of the magmas erupted must reflect loss of moderate amounts (<15%) of olivine and possibly pyroxenes at crustal levels. Fractional crystallization and recharge mixing nearly erase all mantle signatures in the most silicic V. Chichinautzin magmas, so that their origin can only be inferred from their association with the more mafic precursory melts. The pyroxenite model implies that ∼15–18 wt % of the erupted melt mass, and possibly more, is slab-derived. We infer that the elements Fe, Mg, Ca and Ti are principally mantle-derived, whereas significant amounts of the elements Si, K, Na, P and possibly Al may be contributed from slab. As blends of mantle and slab materials, the OIB-type Texcal Flow and V. Chichinautzin magmas provide limited indication of the composition of the sub-arc mantle prior to subduction modification, which is inferred to be similar to primitive mantle, but less enriched than the sources of the intraplate magmas behind the MVB Volcanic front.
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the origin of a primitive trondhjemite from the trans mexican Volcanic Belt and its implications for the construction of a modern continental arc
Geology, 2008Co-Authors: Arturo Gomeztuena, Laura Mori, Nelly E Rinconherrera, Fernando Ortegagutierrez, Jesus Sole, Alexander IriondoAbstract:A remarkable suite of Miocene high-silica trondhjemites discovered in the central Trans-Mexican Volcanic Belt indicates that slab melts can ascend through the mantle and crust while suffering only minor compositional modifications. Despite carrying an assortment of deep crustal xenoliths, the trondhjemites preserve the most depleted isotopic compositions ever measured in the Mexican arc, with values that are nearly identical to those of the Pacific mid-oceanic-ridge basalts. These rocks also have high Sr/Y ratios, and extremely fractionated heavy rare earth element patterns at relatively high Mg number (Mg#), features that are all consistent with melts from the subducted oceanic crust that had only limited interaction with mantle peridotite during ascent. Nonetheless, modeling results indicate that these unusual geochemical features can be modified by more extensive mantle assimilation, resulting in compositions that could match those of more typical intermediate rocks from Mexico. The data thus indicate that the slab melt component uniquely recorded by the Miocene trondhjemites represents a likely constituent for most Volcanic sequences of the Mexican arc, and suggest that a modern andesitic continental crust can be constructed directly from mantle-modified slab melts without a basaltic precursor.
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effects of prolonged flat subduction on the miocene magmatic record of the central trans mexican Volcanic Belt
Chemical Geology, 2007Co-Authors: Laura Mori, Arturo Gomeztuena, Yue Cai, Steven L. GoldsteinAbstract:Temporal changes in the chemical compositions of middle to late Miocene rocks from the central Trans-Mexican Volcanic Belt elucidate how prolonged flat subduction influences arc magmatism. These are recorded in the Palo Huerfano–La Joya–Zamorano Volcanic Complex (PH–LJ–Z; 12–10 Ma), a group of andesitic to dacitic stratovolcanoes located at ∼500 km from the trench; and in the Queretaro Volcanic Succession (QVS; 9–6 Ma), a basaltic to basaltic–andesitic plateau that stratigraphically overlies the stratovolcanoes. The two rock-groups display trace element patterns that are typical of arc magmas, but the PH–LJ–Z suite shows higher Sr/Yand Gd/Yb ratios than the QVS, and a few PH–LJ–Z samples also display Sr isotopic ratios that are similar to those of the East Pacific Rise mid-ocean ridge basalts. These features are typical of adakitic magmas. In contrast, QVS rocks display an overall weaker subduction signature (e.g. lower Ba/Nb ratios), do not show adakite features, and have lower SiO2/(MgO+Fe2O3 ) ratios at equivalent Mg# (∼40–70), MgO and Na2O contents than the PH–LJ–Z suite. Since Fe in arc magmas is a sensitive proxy of water content or melting pressure, and Na may reflect the thickness of the mantle column that controls the extent of melting, the overall chemical differences of both suites can only be reconciled if they equilibrated with the mantle wedge at roughly the same pressures but with different amounts of dissolved water. Once formed, both magmatic suites also suffered contamination at different crustal levels during ascent, but their primary compositional differences are mainly related to different mechanisms of element recycling that occurred without major changes in the local tectonic configuration. The adakite features of PH–LJ–Z rocks, and their emplacement at a large distance from the trench, are consistent with a sub-horizontal subduction geometry that favored slab melting at relatively low pressures. On the other hand, a protracted flat subduction will most likely produce a gradually cooler thermal structure in the subduction zone, hindering slab melting, and instead favoring slab dehydration and fluid fluxing of the mantle wedge as a mechanism to form the more typical arc Volcanics of the QVS. © 2007 Elsevier B.V. All rights reserved.
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two episodes of volcanism in the wudalianchi Volcanic Belt ne china evidence for tectonic controls on Volcanic activities
Journal of Volcanology and Geothermal Research, 2014Co-Authors: Yongwei Zhao, Qicheng Fan, Haibo ZouAbstract:Abstract The NNW striking Wudalianchi Cenozoic Volcanic Belt (WVB) in NE China is mainly composed of volcanoes in Menlu River area, Keluo, Wudalianchi and Erkeshan. K–Ar radiometric dating suggests two episodes of volcanism in the WVB. Specifically, the Pliocene to early Pleistocene volcanism is distributed only in the northern part of WVB, whereas middle Pleistocene to Holocene volcanism occurred over the entire WVB. Geomorphological analyses further delineate four northeast-striking linear alignments of cones in the Wudalianchi and Keluo Volcanic fields, probably related to magma feeding fractures with en echelon arrangement. No age progression is observed along these alignments. We propose that a NNW-trending rift may have controlled the eruption from Pliocene to early Pleistocene and a dextral transpression stress field may have influenced the volcanism from middle Pleistocene to Holocene. We suggest that the Pliocene and early Pleistocene volcanism is associated with far effect of the India–Eurasia collision, while the middle Pleistocene to Holocene volcanism in WVB may have resulted from interaction between the India–Eurasia collision and the subduction of the Pacific plate.
