Andean andesites and crustal growth

1981 ◽  
Vol 301 (1461) ◽  
pp. 305-320 ◽  
Keyword(s):  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Parental Magma ◽  
Alkaline Magmatism ◽  
Chemical Compositions ◽  
Crustal Growth ◽  
Calc Alkaline ◽  
Asthenospheric Mantle ◽  
The Andes ◽  
Variable Extent

Over the last 200 Ma, the ensialic Andean plate margin has been characterized by calc-alkaline magmatism. The early (Mesozoic), activity was dominantly of basaltic volcanism while the Cainozoic volcanism was of intermediate, calc-alkaline character. The restriction of Recent volcanism to parts of the Andes underlain by thick wedges of asthenospheric mantle, and the Sr and Nd isotopic relations, indicate that the calc-alkaline parental magmas are derived from the asthenospheric mantle. There is no unequivocal geochemical and geophysical evidence that continental crust or sediment has contributed to the mantle source for Andean magmatism. The chemical compositions of the calc-alkaline volcanic rocks of the active volcanic zones are controlled by fractional crystallization, whereas O-Sr isotopic relations reflect crustal interaction of mantle-derived parental magma with the sialic basement of the Andes. The variable extent of fractional crystallization, partial melting, and mixing of crustal contaminant are related to the variable thickness and age of crust in the different volcanic provinces. Calc-alkaline magmatism was largely responsible for post-Mesozoic crustal growth in the Andes and would have depleted the underlying mantle unless balanced by circulation within the asthenospheric mantle wedge. In terms of net growth of the South American continent, it is not certain where the balance lies between growth by magmatic addition and shrinking by erosion.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

2021 ◽  
pp. 1-22
Author(s):  
Jia-Hao Jing ◽  
Hao Yang ◽  
Wen-Chun Ge ◽  
Yu Dong ◽  
Zheng Ji ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Ne China ◽  
Asthenospheric Mantle ◽  
High K ◽  
Wide Range ◽  
Great Xing’An Range ◽  
Subducting Slab

Abstract Late Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

scholarly journals Non-subduction petrological mechanisms for the growth of the neoarcheam continental crust of the Kola–Norwegian terrane, Fennoscandian shield: geological and isotope-geochemical evidence

2019 ◽  
Vol 27 (2) ◽  
pp. 161-186
Author(s):  
A. B. Vrevskii
Keyword(s):  
Continental Crust ◽  
Greenstone Belt ◽  
Geochemical Modeling ◽  
Volcanic Rocks ◽  
Fennoscandian Shield ◽  
Crustal Growth ◽  
Calc Alkaline ◽  
Geochemical Evidence

The paper reports new data on the composition and age of the Neoarchean calc-alkaline volcanic rocks of the Uraguba–Kolmozero–Voron’ya greenstone belt (UKV GB). Petrological-geochemical modeling indicates a polygenetic origin of primary melts of the basalt–andesite–dacite association and non-subduction geodynamic mechanisms for the crustal growth in the largest greenstone belt of the Kola–Norwegian Block of the Fennoscandian shield.

Magnetite–apatite intrusions and calc-alkaline magmatism, Camsell River, N.W.T.

1976 ◽  
Vol 13 (2) ◽  
pp. 348-354 ◽  
Author(s):  
J. P. N. Badham ◽  
R. D. Morton
Keyword(s):  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Alkaline Magmatism ◽  
Calc Alkaline ◽  
Immiscible Liquids ◽  
Intermediate Composition ◽  
Andean Type

The Camsell River area comprises a roof pendant of volcanic rocks within an Aphebian (~1800 m.y.) orogenic belt. Magnetite–apatite intrusions and related bodies are common and are closely associated with plutons of intermediate composition. The magnetitic intrusions are interpreted as immiscible liquids that separated from a magma of intermediate composition. The immiscible fractions were predominantly crystalline when they reached their present higher levels, and final emplacement was facilitated by volatile-streaming and fluidization. Their presence in the orogenic belt is taken as further support for the hypothesis that the orogen was of Andean type.

Eocene Challis-Kamloops volcanism in central British Columbia: an example from the Buck Creek basin

1998 ◽  
Vol 35 (8) ◽  
pp. 951-963 ◽  
Author(s):  
J Dostal ◽  
D A Robichaud ◽  
B N Church ◽  
P H Reynolds
Keyword(s):  
British Columbia ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Fractional Crystallization ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
The United States ◽  
Calc Alkaline ◽  
Heavy Rare Earth Element

Eocene volcanic rocks of the Buck Creek basin in central British Columbia are part of the Challis-Kamloops volcanic belt extending from the United States across British Columbia to central Yukon. The volcanic rocks include two units, the Buck Creek Formation, composed of high-K calc-alkaline rocks with predominant andesitic composition, and the overlying Swans Lake unit made up of intraplate tholeiitic basalts. Whole rock 40Ar/39Ar data for both units show that they were emplaced at 50 Ma. They have similar mantle-normalized trace element patterns characterized by a large-ion lithophile element enrichment and Nb-Ta depletion, similar chondrite-normalized rare earth element patterns with (La/Yb)n ~4-14 and heavy rare earth element fractionation, and overlapping epsilonNd values (2.4-3.1) and initial Sr-isotope ratios ( ~ 0.704). These features suggest derivation of these two units from a similar mantle source, probably garnet-bearing subcontinental lithosphere. The differences between tholeiitic and calc-alkaline suites can be due, in part, to differences in the depth of fractional crystallization and the crystallizing mineral assemblage. Fractional crystallization of the calc-alkaline magmas began at a greater (mid-crustal) depth and included fractionation of Fe-Ti oxides. The volcanic rocks are probably related to subduction of the Farallon plate under the North American continent in a regime characterized by transcurrent movements and strike-slip faulting.

New FTIR data of calc-alkaline volcanic rocks from the Oas-Gutai Mts. and post eruption effects on the water content of phenocrysts

2020 ◽  
Author(s):  
Ákos Kővágó ◽  
Marinel Kovacs ◽  
Dóra Kesjár ◽  
Csaba Szabó ◽  
István Kovács
Keyword(s):  
Water Content ◽  
Volcanic Rocks ◽  
Parental Magma ◽  
Volcanic Eruptions ◽  
Ftir Spectra ◽  
Future Research ◽  
Calc Alkaline ◽  
Structural Hydroxyl ◽  
Volcanic Facies ◽  
Water Contents

<p>We studied volcanic rocks from the Oas-Gutai Mts. (Transylvania, Romania) to measure the ‘structural hydroxyl’ content of the nominally anhydrous minerals (NAMs such as clinopyroxene, plagioclase, quartz), from which water content of the parental magma can be estimated.  The Neogene volcanic chain of the Carpathian-Pannonian region (CPR), due to petrologic variability, is an excellent area for such investigation.</p><p>Recent FTIR studies on the calc-alkaline rocks from CPR, showed that the ‘structural hydroxyl’ content of NAMs could be modified during and after volcanic eruptions [1], [2], [3]. However, transmission FTIR-microscopy is an adequate technique for recognizing this these changes because FTIR spectra of the NAMs indicate signs in the case of hydroxyl loss [4].</p><p>For studying the pre-eruptive water contents clinopyroxenes are the most promising mineral because it has one of the lowest diffusion rates for hydroxyl in NAMs [5]. With the detailed study of the clinopyroxenes FTIR spectra, conclusions can be drawn concerning the potential post-eruptive loss of hydroxyl [4].</p><p>We have examined 8 volcanic rock samples, four dacite samples from Oas and one basalt two andesite and one rhyolite sample from the Gutai Mts. The samples show diverse volcanic facies such as lava, ignimbrite and debris avalanche. The diversity of samples is important for future research because it will help to choose the most adequate volcanic facies to estimate the magmatic equilibrium water contents.</p><p>The studied clinopyroxenes contain 83-371 ppm ‘structural hydroxyl’ content,which can be considered as normal values compared to the work of [6] where ‘structural hydroxyl’ content in clinopyroxenes show a range from 75 to 390 ppm in the mafic calc-alkaline lavas from Salina, Italy.</p><p>[1] Lloyd, A.S., Ferriss, E., Ruprecht, P., Hauri, E.H., Jicha, B.R., & Plank, T. (2016): Journal of Petrology, 57, pp. 1865-1886</p><p>[2] Biró, T., I. Kovács, D. Karátson, R. Stalder, E. Király, G. Falus, T. Fancsik, J. & Sándorné Kovács (2017): American Mineralogist, 102, pp.</p><p>[3] Pálos, Z., Kovács, I. J., Karátson, D., Biró, T., Sándorné Kovács, J., Bertalan, É., & Wesztergom, V. (2019): Central European Geology, 62(1)</p><p>[4] Patkó, L., Liptai, N., Kovács, I., Aradi, L., Xia, Q.K., Ingrin, J., Mihály, J., O'Reilly, S.Y., Griffin, W.L., Wesztergom, V., & Szabó, C. (2019): Chemical Geology, 507, pp. 23-41.</p><p>[5] Farver, J.R. (2010): Reviews in Mineralogy and Geochemistry, 72 (1), pp. 447–507.</p><p>[6] Nazzareni, S., Skogby H., & Zanazzi, P.F. (2011): Contributions to Mineralogy and Petrology, 162, pp. 275–288.</p>

An early Proterozoic volcanic arc succession in southeastern Wyoming

1984 ◽  
Vol 21 (4) ◽  
pp. 415-427 ◽  
Author(s):  
Kent C. Condie ◽  
Craig A. Shadel
Keyword(s):  
Fractional Crystallization ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Alkaline Basalt ◽  
Calc Alkaline ◽  
Early Proterozoic ◽  
Enriched Mantle ◽  
Sierra Madre ◽  
Felsic Volcanic

The Green Mountain Formation of early Proterozoic age in the Sierra Madre Range of southeastern Wyoming comprises a bimodal mafic and felsic volcanic assemblage. The rocks, which are chiefly breccias, agglomerates, flows, and volcaniclastic sediments, represent both subaerial and submarine eruptions and in part were redeposited in fluvial and nearshore marine environments. Volcanic rocks are clearly calc-alkaline in character and share a large number of geochemical features in common with continental-margin arcs or evolved oceanic-arc systems.The low Mg numbers and Ni contents of the basalts require 30–40% olivine fractional crystallization, and the high contents of the most incompatible elements, high (La/Sm)N ratios, and low Zr/Nb ratios require an undepleted or enriched mantle source. Geochemical data are consistent with an origin for the felsic volcanics and associated Encampment River granodiorite by shallow fractional crystallization of calc-alkaline basalt in a tectonic setting similar to modern arc systems. The near absence of andesites may reflect the retention of andesitic magma in crustal reservoirs during fractional cyrstallization.

scholarly journals Geochronology and Sr–Nd–Hf isotope constraints on the petrogenesis of teschenites from the type-locality in the Outer Western Carpathians

2019 ◽  
Vol 70 (3) ◽  
pp. 222-240 ◽  
Author(s):  
Irena Brunarska ◽  
Robert Anczkiewicz
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Volcanic Rocks ◽  
Mantle Metasomatism ◽  
Alkaline Magmatism ◽  
Asthenospheric Mantle ◽  
Depleted Mantle ◽  
Outer Western Carpathians ◽  
Wide Range ◽  
Mantle Component

Abstract The Teschenite Association Rocks (TAR) in the Outer Western Carpathian (OWC) flysch form a classic suite of alkaline intrusions where teschenite and picrite were first defined. They represent continental intraplate volcanism that produced a wide range of melano- to mesocratic rocks emplaced during the Early Cretaceous rifting within the southern margin of the European Plate. Geochemical modelling indicates that they may be a product of ~2–5 % partial melting of the metasomatised, asthenospheric mantle. The variations in REE (low / heavy REE content, LaN/YbN = 11–34) are consistent with deep melting of garnet peridotite. Initial ε(Nd)i = 5.0–6.3 and ε(Hf)i = 4.9–10.0 preclude the significant mature crust involvement. Instead, a linear array formed by the 143Nd/144Nd and 176Hf/177Hf isotopic ratios points to a genesis from the mixed, HIMU–OIB source with the more depleted, MORB-type component. Mantle metasomatism was most likely caused by the Variscan subduction–collision processes as indicated by the depleted mantle Nd model ages. The isotope and trace element ratios of the TAR resemble the European Asthenospheric Reservoir (EAR) — the common mantle end-member for the widespread Cenozoic volcanic rocks in Europe. This confirms a long-term existence of the EAR mantle component beneath the Central Europe, at least since the Early Cretaceous. In situ laser-ablation ICP-MS U–Pb dating of titanite indicates short duration of mafic alkaline magmatism in the OWC, lasting from 123.7 ± 2.1 to 117.9 ± 1.8 Ma. Emplacement of the TAR is correlated with the maximum lithospheric thinning that triggered adiabatic decompression and partial melting of the upwelling asthenospheric mantle. Magmatism ceased most likely due to transition to the dominantly compressive regime associated with the major stress field reorganization directly preceding the Carpathian– Alpine Orogeny.

Time-evolution of magma sources in a continental back-arc setting: the Cenozoic basalts from Sierra de San Bernardo (Patagonia, Chubut, Argentina)

2008 ◽  
Vol 145 (5) ◽  
pp. 714-732 ◽  
Author(s):  
SANDRO BRUNI ◽  
MASSIMO D'ORAZIO ◽  
MIGUEL J. HALLER ◽  
FABRIZIO INNOCENTI ◽  
PIERO MANETTI ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Volcanic Rocks ◽  
Late Eocene ◽  
Early Miocene ◽  
Alkaline Magmatism ◽  
Pb Isotope ◽  
Asthenospheric Mantle ◽  
Magma Sources ◽  
Oceanic Plates ◽  
Patagonian Andes

AbstractEast of the Patagonian Andes, mafic volcanic rocks (mainly lava flows and scoriae) are exposed in the Sierra de San Bernardo fold belt and neighbouring areas (central Patagonia; 44.5–46° S, 69–71° W). They were erupted over a wide interval of time (late Eocene–Pleistocene; 14 new K–Ar ages), and show systematic chemical and Sr–Nd–Pb isotopic variations in time. The alkaline lavas (Mg number 57–66) erupted during the late Eocene and early Miocene, have an intraplate geochemical affinity, and have the highest 143Nd/144Nd and 206Pb/204Pb and the lowest 87Sr/86Sr ratios of the dataset. Their compositions indicate that their depth of equilibration in the mantle was greater than that of subsequent lavas. In contrast, the Plio-Pleistocene alkaline lavas (Mg number 58–71) are the most enriched in incompatible elements, still showing an intra-plate signature, and have the lowest 143Nd/144Nd and 206Pb/204Pb and the highest 87Sr/86Sr ratios. A distinctive group of early Miocene subalkaline lavas is characterized by slightly more evolved compositions (Mg number 56–59), coupled with very low incompatible element contents, flat LREE and fractionated HREE patterns (‘kinked’ pattern), and intermediate Sr–Nd–Pb isotope compositions. The Pleistocene basanites (Mg number 71–72) from the Cerro Ante monogenetic cone, on the easternmost slopes of the Patagonian Andes, have a marked orogenic geochemical signature and Sr–Nd–Pb isotope ratios that overlap with those of volcanic rocks from the adjacent active Andean arc. They originated in a mantle source extensively modified by the addition of materials from the subducting Pacific oceanic plates. We suggest that the wide chemical and isotopic variability of the Sierra de San Bernardo lavas reflects the upwelling of asthenospheric mantle beneath the study area, which induced lithospheric erosion and progressive involvement of enriched mantle domains in the genesis of magmas. In this context, late Eocene and early Miocene alkaline magmatism was dominantly sourced from the asthenospheric mantle, whereas Plio-Pleistocene alkaline magmas contain the largest proportion of an enriched lithospheric component. The peculiar compositional features of the early Miocene subalkaline lavas are interpreted in terms of high-degree mantle melting followed by melt–lithospheric mantle reaction processes. Based on current knowledge about the relative movement and decoupling between lithosphere and asthenosphere, we propose that the asthenosphere below the study area rose up to compensate for the westward drift of the mantle wedge coupled with the South American lithosphere.

Calc-alkaline volcanic rocks from NW Sardinia: Evaluation of a fractional crystallization model

1977 ◽  
Vol 40 (4) ◽  
pp. 253-259 ◽  
Author(s):  
J. Dostal ◽  
S. Capedri ◽  
C. A. R. Albuquerque
Keyword(s):  
Fractional Crystallization ◽  
Volcanic Rocks ◽  
Calc Alkaline

scholarly journals Chemical composition of volcanic glasses in visible tephra layers found in a 2503 m deep ice core from Dome Fuji, Antarctica

2004 ◽  
Vol 39 ◽  
pp. 576-584 ◽  
Author(s):  
Mika Kohno ◽  
Yoshiyuki Fujii ◽  
Takafumi Hirata
Keyword(s):  
Ice Core ◽  
Volcanic Rocks ◽  
Ice Cores ◽  
Tholeiitic Basalt ◽  
South Shetland Islands ◽  
Clear Correlation ◽  
Chemical Compositions ◽  
Element Abundances ◽  
The Andes ◽  
Tephra Layers

AbstractTwenty-six ash layers were found in a 2503 m deep ice core from Dome Fuji station, East Antarctica. In order to gain information about the sources of ash particles found in the layers, major and trace element abundances have been measured. The particles found in 21 of the 26 layers were commonly a few tens of μm in size, suggesting that they originated from volcanoes located in and around the Antarctic. On the basis of comparison of the major-element compositions of these tephras with reference to volcanic rocks and ash, the tephras were divided into three types: (1) tholeiitic basalt to dacite, (2) calc-alkaline andesite, and (3) trachyandesite to trachyte. The source regions appear to be (1) South Sandwich Islands, Southern Ocean, (2) South Shetland Islands, Antarctica, and/or a southern part of the volcanic zone of the Andes, and (3) Marie Byrd Land and/or Victoria Land, Antarctica, respectively. The tephras found in the other five ash layers were significantly smaller (< 5 μm), suggesting that they traveled over longer distances. Abundances of trace elements for the alkaline tephra collected from one layer revealed a possible genetic link to volcanic rocks from Marie Byrd Land. In order to correlate between ice cores from Dome Fuji and Vostok, Antarctica, which are widely separated, we found coeval ash layers serving as stratigraphic markers of Antarctic ice cores. A comparison of profiles of 18O/16O (δ18O) and 2H/1H (δD) for the Dome Fuji and Vostok cores indicates that eight ash layers are equivalent in the two cores. A clear correlation was found for the chemical compositions of six of these ash layers, indicating a high potential for key correlation beds between the deep ice cores from Dome Fuji and Vostok.

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