scholarly journals Upper Cretaceous intrusives in the Coastal Cordillera near Valdivia: forearc magmatism related to the passage of a triple junction?

2021 ◽  
Vol 48 (1) ◽  
pp. 24
Author(s):  
Denisse De la Fuente ◽  
Óscar Figueroa ◽  
Daniel Demaiffe ◽  
Mauricio Mella ◽  
Paul Duhart ◽  
...  
Keyword(s):  
Upper Cretaceous ◽  
Limited Extent ◽  
Calc Alkaline ◽  
Coastal Cordillera ◽  
Andean Cordillera ◽  
Upper Paleozoic ◽  
S 100 ◽  
Plutonic Rocks ◽  
Subduction Setting ◽  
Porphyritic Texture

Upper Cretaceous intrusives of limited extent crop out in the Coastal Cordillera near of Valdivia (39º48’ S), 100 km west of the main topographic divide of the Andean Cordillera. Given that plutonic rocks of the same age crop out at the same latitudes in the high Andes the coastal intrusives emplaced in a forearc position in the upper plate of a subduction setting. They correspond to hypabyssal intrusives displaying mainly porphyritic texture and lithological variations with microtonalites (minor), porphyritic microgranodiorites (main) and microgranites. They intrude the Upper Paleozoic-Triassic accretionary complex of the Bahia Mansa Metamorphic Complex. These intrusives, that comprise the Chaihuín Pluton and minor stocks of porphyritic felsic rocks, have calc-alkaline affinities with metaluminous and peraluminous character. They are geochemically similar to the contemporaneous main arc-related plutonic rocks of the Gualletué Plutonic Group. The microgranitoids and dacitic rocks from Los Boldos, the low and Loncoche are peculiar because they show an apparently adakitic affinity in Sr/Y and LaN/YbN discriminant diagrams; nevertheless Sr contents of these rocks (

Laramide to Miocene syn-extensional plutonism in the Puerta del Sol area, central Sonora, Mexico

2017 ◽  
Vol 34 (1) ◽  
pp. 45 ◽  
Author(s):  
Elizard González-Becuar ◽  
Efrén Pérez-Segura ◽  
Ricardo Vega-Granillo ◽  
Luigi Solari ◽  
Carlos Manuel González-León ◽  
...  
Keyword(s):  
Metamorphic Core Complex ◽  
Primitive Mantle ◽  
Isotopic Ratios ◽  
Magmatic Evolution ◽  
Calc Alkaline ◽  
Core Complex ◽  
High K ◽  
Sierra Madre ◽  
Plutonic Rocks ◽  
Metamorphic Core

Plutonic rocks of the Puerta del Sol area, in central Sonora, represent the extension to the south of the El Jaralito batholith, and are part of the footwall of the Sierra Mazatán metamorphic core complex, whose low-angle detachment fault bounds the outcrops of plutonic rocks to the west. Plutons in the area record the magmatic evolution of the Laramide arc and the Oligo-Miocene syn-extensional plutonism in Sonora. The basement of the area is composed by the ca. 1.68 Ga El Palofierral orthogneiss that is part of the Caborca block. The Laramide plutons include the El Gato diorite (71.29 ± 0.45 Ma, U-Pb), the El Pajarito granite (67.9 ± 0.43 Ma, U-Pb), and the Puerta del Sol granodiorite (49.1 ± 0.46 Ma, U-Pb). The younger El Oquimonis granite (41.78 ± 0.32 Ma, U-Pb) is considered part of the scarce magmatism that in Sonora records a transition to the Sierra Madre Occidental magmatic event. The syn-extensional plutons are the El Garambullo gabbro (19.83 ± 0.18 Ma, U-Pb) and the Las Mayitas granodiorite (19.2 ± 1.2 Ma, K-Ar). A migmatitic event that affected the El Palofierral orthogneiss, El Gato diorite, and El Pajarito granite between ca. 68 and 59 Ma might be related to the emplacement of the El Pajarito granite. The plutons are metaluminous to slightly peraluminous, with the exception of El Oquimonis granite, which is a peraluminous two-mica, garnet-bearing granite. They are mostly high-K calc-alkaline with nearly uniform chondrite-normalized REE and primitive-mantle normalized multielemental patterns that are characteristic of continental margin arcs and resemble patterns reported for other Laramide granites of Sonora. The Laramide and syn-extensional plutons also have Sr, Nd and Pb isotopic ratios that plot within the fields reported for Laramide granites emplaced in the Caborca terrane in northwestern and central Sonora. Nevertheless, and despite their geochemical affinity to continental magmatic arcs, the El Garambullo gabbro and Las Mayitas granodiorite are syn-extensional plutons that were emplaced at ca. 20 Ma during development of the Sierra Mazatán metamorphic core complex. The 40Ar/39Ar and K-Ar ages obtained for the El Palofierral orthogneiss, the Puerta del Sol granodiorite, the El Oquimonis granite, and the El Garambullo gabbro range from 26.3 ± 0.6 to 17.4 ± 1.0 Ma and are considered cooling ages associated with the exhumation of the metamorphic core complex.

Felsic plutonic rocks from the southern portion of the New Caledonian Ultramafic Belt

1973 ◽  
Vol 110 (5) ◽  
pp. 431-446 ◽  
Author(s):  
K. A. Rodgers
Keyword(s):  
New Caledonia ◽  
Ultramafic Rocks ◽  
Calc Alkaline ◽  
Mafic Rocks ◽  
Alkaline Magma ◽  
Southwest Pacific ◽  
Plutonic Rocks

SummaryGranodiorite stocks were intruded into the alpine peridotites of southern New Caledonia in the Eocene following overthrusting of the ultramafics onto the sialic core of the island. Strong zoning, from mela-diorite to granodiorite, is developed in one pluton and is believed to be the result of assimilation of ultramafic and mafic rocks by the calc-alkaline magma. Evidence in favour of a consanguineous relationship between the felsic and ultramafic rocks is largely circumstantial. In their petrography, mineralogy and chemistry, the rocks show few differences from other felsic plutonics of Tertiary age in the southwest Pacific.

Norito e charnoenderbitos da borda do maciço intrusivo de Venda Nova, Espírito Santo

2002 ◽  
Vol 25 ◽  
pp. 99-124
Author(s):  
Julio Cezar Mendes ◽  
Cristina Maria Wiedemann ◽  
Ian McReath
Keyword(s):  
Calc Alkaline ◽  
Espírito Santo ◽  
Fine Grained ◽  
Massive Structure ◽  
Incompatible Elements ◽  
Residual Phase ◽  
Depleted Mantle ◽  
Espirito Santo ◽  
Porphyritic Texture ◽  
Narrow Ring

An irregular and narrow ring of charnoenderbites and norite envelopes gabbros and syenomonzonites in the Venda Nova inversely zoned pluton, Espírito Santo. The former have an almost massive structure, with foliation only locally well marked. The norite is a fine-grained cumulatic rock with granular hypidiomorphic to intergranular texture. The medium-grained charnoenderbites comprise enderbites, Opx-quartzdiorites and Opx-granodiorites. They are leucocratic to mesocratic with granular hypidiomorphic to porphyritic texture. Ortho and clinopyroxene are present in the both lithotypes. Subsolidus textures occur in the norite and charnoenderbites. The whole rock chemistry separates two different sequences: a basic one, with tholeiitic affinities, correspond to the noritic cumulate, and an intermediary one, medium-K calc-alkaline, comprising the charnoenderbites. They show clearly different chemical signature when compared to the alkalic affinity rocks of the inner domain of the pluton. Both the sequences have similar geochemical characteristics: they are metaluminous, Ca, Fe and Al enriched, and have low to moderate incompatible elements contents. Normal to depleted mantle protolith is inferred for both sequences, and garnet probably was a residual phase during the mantle partial melting.

Igneous history of the Andean Cordillera and Patagonian plateau around latitude 46°S

1981 ◽  
Vol 303 (1474) ◽  
pp. 105-149 ◽  
Keyword(s):  
Calc Alkaline ◽  
Alkali Basalts ◽  
Cinder Cones ◽  
Andean Cordillera ◽  
The Pacific ◽  
Igneous Activity ◽  
History Of ◽  
Pacific Margin ◽  
Rhyolite Volcanism ◽  
Back Arc

From the Middle Jurassic onwards persistent igneous activity in the southern Andes around 46 °S was controlled by easterly dipping subduction along the Pacific margin. Cogenetic plutonic rocks belonging to the Patagonian batholith, and calc-alkaline volcanics ranging from basaltic andesites to rhyolitic tuffs and ignimbrites are the principal products. Erosion of the primary volcanics has led at various times to the development of thick volcaniclastic sequences, for example in the Cretaceous-Lower Tertiary Divisadero formation. The Coyhaique region marks the northerly extension of a narrow back-arc basin in which the marine Neocomian successions accumulated. Volcaniclastics from the island arc, which presumably lay to the west, are intercalated with the sediments. Although the marine basin was short-lived a mildly extensional back-arc regime may have existed through much of Mesozoic-Recent times. Widespread basalt-rhyolite volcanism on the eastern side of the cordillera seems to have been associated with this tectonic environment. Remnants of the Patagonian basalt plateau at latitude 45-47 °S extend from the Argentine-Chile frontier to Lago Colhue Huapi. Four principal age and compositional groups have been distinguished in the lavas, (i) The oldest, which are about 80 Ma, occur in sections at Senguerr and Morro Negro. They are almost exclusively tholeiitic, but show some calc-alkaline affinities and resemble in other respects basalts from marginal basins, (ii) The second group (57-43 Ma) occur in the lower part of the Chile Chico section with a compositional spread from olivine tholeiites through alkali basalts to one occurrence of a basanite. (iii) The upper part of the main plateau sequence, where the flows are in the range 25-9 Ma, are dominantly of alkali basalt composition, (iv) Post-plateau flows from small cinder cones on the surface of the plateau range in age from ca. 4 Ma to 0.2 Ma or less. They are mostly highly undersaturated basanites, with occasional leucite basanites, enriched in incompatible elements. A few of the earlier tholeiites with calc-alkali traits may have been closely associated with subduction or marginal basin processes. The younger lavas are more alkalic intraplate types generated in the remote back-arc extensional zone.

scholarly journals The enriched Variscan lithosphere of NE Iberia: data from postcollisional Permian calc-alkaline lamprophyre dykes of Les Guilleries

2021 ◽  
Vol 19 ◽  
pp. 1-23
Author(s):  
Esteban Mellado ◽  
Mercè Corbella ◽  
Didac Navarro ◽  
Andrew Kylander
Keyword(s):  
Mantle Source ◽  
Lithospheric Mantle ◽  
Subcontinental Lithospheric Mantle ◽  
Volatile Content ◽  
Calc Alkaline ◽  
Geochronological Data ◽  
Metamorphic Basement ◽  
Lithospheric Mantle Source ◽  
Porphyritic Texture ◽  
Alkaline Lamprophyres

Post-collisional mafic dykes crosscut the Paleozoic metamorphic basement and late-Variscan plutons in Les Guilleries massif (Catalan Coastal Ranges, NE Iberia). The predominance of mafic phenocrysts, porphyritic texture, abundant amphibole, high MgO and volatile content, together with crustal-like trace-element patterns indicate that the dykes correspond to calc-alkaline lamprophyres, mainly spessartites. Their enrichment in LILE, HFSE and REE and initial Sr-Nd isotopic compositions (87Sr/86Sri between 0.70851 and 0.71127, epsilon Ndi between -5.23 and -4.63) are consistent with an enriched subcontinental lithospheric mantle source. U-Pb ages of matrix titanite crystals yield concordia ages of 262±7Ma, congruent with crosscutting relationships. Postmagmatic processes are evidenced by intense chloritization and albitization of the lamprophyres, together with systematic variations of Na2O vs SiO2, K2O, CaO, Ba, Rb, Cs, Pb, Sr, Tl, and Zn, and possibly the removal of F. The geochemical and geochronological data support an orogenic geochemical affinity, in accordance with the transitional tectonic regime between Variscan compression/transpression and post-collisional transtension/extension, related to the fragmentation of Pangea and thinning of the lithosphere. The lamprophyre dykes studied could represent the youngest pulse of Variscan orogenic magmatism and, therefore, mark its end in NE Iberia before the onset of the generalized Triassic extension.

Stratigraphy, geochemistry, and petrology of the Upper Cretaceous volcanic arc sequence north of Istanbul, Pontides, NW Turkey

2021 ◽  
Author(s):  
Cemre Ay ◽  
Gürsel Sunal ◽  
Aral I. Okay
Keyword(s):  
Black Sea ◽  
Upper Cretaceous ◽  
High Ratio ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
The Black Sea ◽  
Calc Alkaline ◽  
High K ◽  
Nw Turkey ◽  
Pattern Display

<p>Upper Cretaceous arc-related volcanic and volcanoclastic units overlying the Paleozoic sedimentary rocks of the Istanbul Zone are a key unit related to the opening of the Black Sea as a back-arc basin. They formed as a result of north dipping subduction of the Neo-Tethys Ocean beneath Laurasia. We studied the Upper Cretaceous volcanic units north of Istanbul along several stratigraphic sections, and present new geochemical data from the volcanic rocks in order to understand Cretaceous geodynamic evolution of the İstanbul Zone.</p><p>The Upper Cretaceous  volcanic units north of Istanbul are divided into two formations. At the base there is a fore-arc turbidite succession,the İshaklı Formation, which is made up of volcaniclastic sandstone, shale, marl, tuff, debris flow horizons and epiclastic rocks of Turonian age. The İshaklı Formation is conformably overlain by the volcanoclastics,  tuffs, andesite and basalt lavas and agglomerates- the Riva Formation, which represents the arc/ intra-arc series.</p><p>Geochemically, basalts and basaltic andesites of the Riva Formation are low K calc-alkaline to medium-high K calc-alkaline and with magnesium numbers ranging from 32.6% to 51.5% Primitive mantle normalized spider diagram of trace elements show  enrichment in LILE elements (K, Rb, Sr, Cs, Ba, Th and U) and depletion in HFS elements ( Nb,Ta and Ti) . The high ratio of LILE/ HFS and negative Nb-Ta anomalies indicate that the volcanism evolved in subduction setting. Chondirite-normalized REE pattern display slight negative Eu anomalies and the La/Yb ratios of the samples range between 2,76 and 4,89. Our new geochemical, stratigraphical and the regional geological data suggest that north of Istanbul there was a transition from fore-arc deposition to arc volcanism during the Late Cretaceous opening of the Western Black Sea.  Considering the whole Pontide – Sredna-Gora Upper Cretaceous magmatic arc, it can be stated that calc-alkaline volcanism developed in relation to northward subduction of the Neo-Tethys oceanic lithosphere during the Turonian, and may have passed into high-K calc alkaline and shoshonitic magmatism as a result of the progressive extentional tectonism during the Campanian.</p>

Correlation among lower to upper crustal components in an island arc: the Jurassic Bonanza arc, Vancouver Island, Canada

1999 ◽  
Vol 36 (8) ◽  
pp. 1371-1413 ◽  
Author(s):  
Susan M DeBari ◽  
Robert G Anderson ◽  
James K Mortensen
Keyword(s):  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Vancouver Island ◽  
Island Arc ◽  
Calc Alkaline ◽  
Queen Charlotte Islands ◽  
Basement Rocks ◽  
Plutonic Rocks ◽  
Differential Uplift ◽  
Age Range

The Westcoast Crystalline Complex (WCC), Island Intrusions, and Bonanza Group of Vancouver Island, Canada, form three different crustal levels of the Early to Middle Jurassic Bonanza island arc. Differential uplift has exposed the plutonic roots and the volcanic carapace of the arc for a strike length of ~500 km, and for another 250 km on the Queen Charlotte Islands. At deeper crustal levels within the arc, influx of mantle-derived magmas was accompanied by metamorphism and melting of Wrangellian basement rocks, yielding the heterogeneous WCC. Upward mobilization and hybridization of magmas to shallower levels in the crust resulted in the batholiths of the Island Intrusions and the lavas and pyroclastic rocks of the Bonanza Group. New U-Pb crystallization ages for plutonic rocks of the arc span an age range of 190.3 ± 1.0 to 168.6 ± 5.3 Ma. Ages of the WCC and western Island Intrusions are indistinguishable and overlap with published fossil and isotopic ages for the Bonanza Group. Younger Middle Jurassic ages for the eastern Island Intrusions overlap with those for plutonic rocks in the southern Coast Belt and Queen Charlotte Islands. All plutonic and volcanic rocks within the arc have overlapping geochemical signatures, supporting their comagmatic origin. All are light rare earth element-enriched with abundances 10-50× chondrites. The most mafic noncumulate gabbroic rocks have compositions typical of island arc basalts, with intermediate values of Al2O3 (16-17 wt.%) and high MgO (7-9 wt.%). More differentiated rocks follow a calc-alkaline trend with concomitant increase in Al2O3 (18-20 wt.%). Their geochemistry indicates varying degrees of mixing with melts of mafic Wrangellian basement.

Pliocene lahar deposits in the Coastal Cordillera of central Chile: Implications for uplift, avalanche deposits, and porphyry copper systems in the Main Andean Cordillera

2006 ◽  
Vol 20 (4) ◽  
pp. 369-381 ◽  
Author(s):  
Alfonso Encinas ◽  
Victor Maksaev ◽  
Luisa Pinto ◽  
Jacobus P. Le Roux ◽  
Francisco Munizaga ◽  
...  
Keyword(s):  
Porphyry Copper ◽  
Central Chile ◽  
Coastal Cordillera ◽  
Andean Cordillera
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