scholarly journals The low-grade basement at Península La Carmela, Chilean Patagonia: new data for unraveling the pre-Permian basin nature of the Eastern Andean Metamorphic Complex

2021 ◽  
Author(s):  
D. Rojo ◽  
M. Calderón ◽  
M. C. Ghiglione ◽  
R. J. Suárez ◽  
P. Quezada ◽  
...  
Keyword(s):  
Low Grade ◽  
Metamorphic Complex ◽  
Permian Basin ◽  
Chilean Patagonia

scholarly journals Progressive Low-Grade Metamorphism Reconstructed from the Raman Spectroscopy of Carbonaceous Material and an EBSD Analysis of Quartz in the Sanbagawa Metamorphic Event, Central Japan

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 854
Author(s):  
Hidetoshi Hara ◽  
Hiroshi Mori ◽  
Kohei Tominaga ◽  
Yuki Nobe
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Metamorphic Event ◽  
Ebsd Analysis ◽  
Low Grade ◽  
Accretionary Complex ◽  
Metamorphic Complex ◽  
Central Japan ◽  
Grade Metamorphism ◽  
Quartz Grains

Low-grade metamorphic temperature conditions associated with the Sanbagawa metamorphic event were estimated by the Raman spectroscopy of carbonaceous material (RSCM) in pelitic rocks and an electron backscatter diffraction (EBSD) analysis of the quartz in siliceous rocks. Analytical samples were collected from the Sanbagawa metamorphic complex, the Mikabu greenstones, and the Chichibu accretionary complex in the eastern Kanto Mountains, central Japan. Previously, low-grade Sanbagawa metamorphism was only broadly recognized as pumpellyite–actinolite facies assigned to the chlorite zone. The RSCM results indicate metamorphic temperatures of 358 °C and 368 °C for the chlorite zone and 387 °C for the garnet zone of the Sanbagawa metamorphic complex, 315 °C for the Mikabu greenstones, and 234–266 °C for the Chichibu accretionary complex. From the EBSD analyses, the diameter of the quartz grains calculated by the root mean square (RMS) approximation ranges from 55.9 to 69.0 μm for the Sanbagawa metamorphic complex, 9.5 to 23.5 μm for the Mikabu greenstones, and 2.9 to 7.3 μm for the Chichibu accretionary complex. The opening angles of the c-axis fabric approximate 40–50°, presenting temperatures of 324–393 °C for the Sanbagawa metamorphic complex and the Mikabu greenstones. The temperature conditions show a continuous increase with no apparent gaps from these low-grade metamorphosed rocks. In addition, there exists an empirical exponential relationship between the estimated metamorphic temperatures and the RMS values of the quartz grains. In this study, integrated analyses of multiple rock types provided valuable information on progressive low-grade metamorphism and a similar approach may be applied to study other metamorphic complexes.

Petrotectonic implications of metabasites of the Eastern Andean Metamorphic Complex at Lago O´Higgins-San Martin, southern Patagonia

2021 ◽  
Author(s):  
Diego Rojo ◽  
Mauricio Calderón ◽  
Matias Ghiglione ◽  
Rodrigo Javier Suárez ◽  
Paulo Quezada ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Crustal Contamination ◽  
Oceanic Lithosphere ◽  
Passive Margin ◽  
Low Grade ◽  
Accretionary Wedge ◽  
Metamorphic Complex ◽  
Marginal Basin ◽  
Southern Patagonia ◽  
San Martín

<p>The Eastern Andean Metamorphic Complex (EAMC) in southwestern Patagonia (4°-52°S) is a 450 km long belt mainly composed by low-grade metasedimentary rocks of Upper Devonian-lower Carboniferous, and Permian-lower Triassic ages. Previous works have suggested a passive margin environment for the deposition of the protolith.  The EAMC comprise scarce interleaved tectonic slices of marbles, metabasites, and exceptional serpentinite bodies. At Lago O´Higgins-San Martin (48°30’S-49°00’S) the metasedimentary sucessions are tectonically juxtaposed with lenses of pillowed metabasalts and greenschists having OIB, N-MORB, BABB and IAT geochemical affinities. The Nd-isotopic composition of metabasalts is characterized by εNd<sub>(t=350 Ma)</sub> of +6 and +7. The metabasalts show no signal of crustal contamination, instead, the mantle source was probably modified by subduction components. New and already published provenance data based on mineralogy, geochemistry and zircon geochronology indicate that the quartz-rich protolith of metasandstones were deposited during late Devonian-early Carboniferous times (youngest single zircon ages around of latest Devonian-earliest Carboniferous times) sourced from igneous and/or sedimentary rocks located in the interior of Gondwana, as the Deseado Massif, for instance. Noticeable, the detrital age patterns of all samples reveal a prominent population of late Neoproterozoic zircons, probably directly derived from igneous and/or metaigneous rocks of the Brasiliano/Pan-African orogen or from reworked material from variably metamorphosed sedimentary units that crops out at the same latitudes in the extra-Andean region of Patagonia. We propose that the protolith of metabasites formed part of the upper part of an oceanic-like lithosphere generated in a marginal basin above a supra-subduction zone, where plume-related oceanic island volcanoes were generated. The closure of the marginal basin, probably in mid-Carboniferous times, or soon after. The oceanic lithosphere was likely underthrusted within an east-to-northeast-dipping subduction zone, where ophiolitic rocks and metasedimentary sequences were tectonically interleaved at the base of an accretionary wedge.</p>

Occurrence of the high grade Thabsila metamorphic complex within the low grade Three Pagodas shear zone, Kanchanaburi Province, western Thailand: Petrology and geochronology

2012 ◽  
Vol 60 ◽  
pp. 68-87 ◽  
Author(s):  
Prayath Nantasin ◽  
Christoph Hauzenberger ◽  
Xiaoming Liu ◽  
Kurt Krenn ◽  
Yunpeng Dong ◽  
...  
Keyword(s):  
Shear Zone ◽  
Low Grade ◽  
High Grade ◽  
Metamorphic Complex

The geochemical and tectonic evolution of the central Karakoram, North Pakistan

1988 ◽  
Vol 326 (1589) ◽  
pp. 229-255 ◽  
Keyword(s):  
Upper Cretaceous ◽  
Crustal Thickening ◽  
Indian Plate ◽  
Contact Aureole ◽  
Low Grade ◽  
Metamorphic Complex ◽  
The South ◽  
Northern Margin ◽  
North Pakistan ◽  
Mantle Component

The Main Karakoram Thrust (MKT) separates the Karakoram Plate from the accreted Kohistan—Ladakh Terranes and Indian Plate to the south. Within the central Karakoram three geologically distinct zones are recognized: from south to north (i) the Karakoram metamorphic complex, (ii) the Karakoram batholith and (iii) the northern Karakoraih sedimentary terrane. Magmatic episodes of Jurassic and mid-Upper Cretaceous age are recognized before India-Asia collision at ca. 50-45 Ma. Both reveal subduction-related petrographic and geochemical signatures typical of Andean-type settings. Associated with the Jurassic event was a low-pressure metamorphism (Ml). Synchronous with the mid-Upper Cretaceous episode was the passive accretion of the Kohistan-Ladakh terrane to the Karakoram and closure of the Shyok Suture Zone (SSZ). The main collision between the Indian and Asian Plates resulted in crustal thickening beneath the Karakoram and development of Barrovian metamorphism (M2). Early postcollisional plutons dated at 36-34 Ma cross-cut regional syn-metamorphic foliations and constrain a maximum age on peak M2 conditions. Uplift of the Karakoram metamorphic complex in response to continued crustal thickening was synchronous with culmination collapse along the inferred Karakoram Batholith Lineament (KBL). A combination of thermal re-equilibration of thickened continental crust and the proposed addition of an enriched mantle component promoted dehydration, partial melting and generation of the Baltoro Plutonic Unit (BPU). It was subsequently emplaced as a hot, dry magma into an extensional mid-crustal environment. A contact aureole (M3) was imposed on the low-grade sediments along the northern margin, whereas isograds in uplifted metamorphic rocks to the south were thermally domed with in situ migmatization.

scholarly journals Analysis of ground water quality in terms of geological setting in the territory of the Mesic village for the purpose of bottling (municipality of Vrsac)

2014 ◽  
Vol 94 (4) ◽  
pp. 91-108
Author(s):  
Dragana Vuskovic ◽  
Ivana Carevic ◽  
Velimir Jovanovic ◽  
Natasa Biocanin
Keyword(s):  
Mineral Water ◽  
Low Grade ◽  
Metamorphic Complex ◽  
Silicate Minerals ◽  
Clay Deposits ◽  
Geological Conditions ◽  
Calcium Magnesium ◽  
Anions And Cations ◽  
Hydrolysis Of

This paper presents an analysis of the quality of groundwater that are exploited in the territory of the Mesic village in the factory "Moja voda" on the slopes of the Vrsac Mountains. Spring waters formed in the Tertiary and Quaternary sediments are situated near the high-grade metamorphic complex border of Vrsac Mountains that represents the northernmost prolongation of Serbo-macedonian massif to the West and low-grade metamorphic complex of the Ranovac-Vlasina-Osogovo terrane to the East. Groundwater is assigned on the basis of chemical analyses to the group of hydrocarbonate-calcium-magnesium non-carbonated low-mineral water, whose physical properties and chemical composition is the consequence of geological conditions of the environment through which circulates. The dominant anions and cations (HCO3 -, Ca2 + and Mg2 +) accumulate in groundwater of Mesic as a product of weathering of silicate minerals present in igneous and metamorphic complex of Vrsac Mountains. The specificity of these waters is an adequate amount of selenium in its composition related to the Tertiary and Quaternary clay deposits which have the pyrite and organic matter, as well as silica, whose presence in the water is a consequence of weathering (hydrolysis) of silicate minerals, particularly feldspar. Water from the exploration wells is classified as ?B reserve? according to the applicable criteria.

scholarly journals Geologic reconnaissance of Lautaro Volcano, Chilean Patagonia

2010 ◽  
Vol 33 (1) ◽  
pp. 177
Author(s):  
Akihisa Motoki ◽  
Yuji Orihashi ◽  
Jose A. Naranjo ◽  
Daiji Hirata ◽  
Pedro Skvarca ◽  
...  
Keyword(s):  
Volcanic Glass ◽  
Biotite Granite ◽  
Low Grade ◽  
Volcanic Zone ◽  
The North ◽  
Chilean Patagonia ◽  
Bread Crust ◽  
Ice Field ◽  
Chile Triple Junction ◽  
North Western

Lautaro is the volcano closest to the Chile Triple Junction in the Andean Austral Volcanic Zone. The volcanic edifice of 3,607 m a.s.l. stands out on the north-western part of the plateau of the South Patagonian Ice Field. The volcano basement is composed of low-grade meta-pelites that are cut by tabular intrusive bodies of hornblende-biotite granite. The volcano is almost completely covered by ice and the study was performed on volcanic detritus present in terminal moraines of the Lautaro Glacier and the tephra on the surface of the O'Higgins Glacier. The terminal moraines of Lautaro Glacier contain fragments of light grey dacite rich in plagioclase and hornblende phenocrysts. Some dacite blocks show prismatic jointing, suggesting an origin of hot emplacement and subsequent rapid cooling, possibly resulted from collapse of a steep lava front. Some samples have glassy groundmass and rhyolite-like flow texture, with presence of mafic inclusions and bread crust bomb texture. The surface of the O'Higgins Glacier is covered by lapilli-size pumice fallout deposit. There are many dirt cones covered by volcanic ash composed of pumice fragments, volcanic glass, quartz, plagioclase, biotite, hornblende, and orthopyroxene. The ash and pumice are similar in chemical composition, both indicating an adakitic signature. At least three layers of fallout deposits have been recognised in parts of the surface of the glacier, which may correspond to the latest known eruptions.

scholarly journals Polyphase white mica growth in low-grade metapelites from La Cebila Metamorphic Complex (Famatinian Belt, Argentina): evidence from microstructural and XRD investigations.

2011 ◽  
Vol 38 (2) ◽  
pp. 268 ◽  
Author(s):  
Sebastian O. Verdecchia ◽  
Gilda Collo ◽  
Edgardo G. Baldo
Keyword(s):  
White Mica ◽  
Low Grade ◽  
Metamorphic Complex ◽  
Mineral Analysis ◽  
Chemical Parameter ◽  
Sierras Pampeanas ◽  
Kübler Index ◽  
Event Based ◽  
Parameter Values

Two tectono-thermal metamorphic events, M1-D1 (S1, with associated white mica and chlorite: WM1-Chl1) and M2-D2 (S2, with development of WM2-Chl2), are established from polyphase white mica growth for low-grade units from the Ordovician metasedimentary successions of La Cebila Metamorphic Complex in the Famatinian belt (western-central Argentina). The thermobarometric characterization of the M1 main event was carried out by means of clay-mineral analysis and crystallo-chemical parameter measurements. Epizonal (temperatures between 300 and 400ºC) and low-pressure conditions are suggested for M1 event, based in Kübler index values ranging from 0.23 to 0.17 Δº2θ, white mica b parameter values between 9.004 and 9.022 Å (mean of 9.014 Å, n=16) and Si contents between 3.13-3.29 a.p.f.u. Temperatures of ~180-270ºC are estimated for the M2 event, with Kübler index values ranging from 0.31 to 0.46 Δº2θ. The M1-D1 event of La Cebila could be linked to highstrain heating tectono-metamorphic Ordovician regime recorded in others complexes from Famatinian foreland region of Sierras Pampeanas.

The geology of Cape Dubouzet, northern Antarctic Peninsula: continental basement to the Trinity Peninsula Group?

1996 ◽  
Vol 8 (4) ◽  
pp. 407-414 ◽  
Author(s):  
Francisco Hervé ◽  
Jorge Lobato ◽  
Ignacio Ugalde ◽  
Robert J. Pankhurst
Keyword(s):  
Antarctic Peninsula ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Metamorphic Complex ◽  
Calc Alkaline ◽  
Magmatic Arc ◽  
The Antarctic ◽  
The Trinity

Cape Dubouzet is mainly composed of a volcanic-subvolcanic complex of extrusive rhyolitic breccias, a banded rhyolite and a semi-annular body of dacite porphyry rich in xenoliths of metamorphic rocks. Major and REE geochemistry indicate that the volcanic rocks are calc-alkaline and that they are genetically related by fractional crystallization of a plagioclase-bearing assemblage from a common magma. Rb-Sr data suggest that the rhyolitic complex is of Middle-to-Late Jurassic age, and that it is intruded by Late Cretaceous stocks of banded diorite and gabbro. All these rocks are partially covered by moraines whose clasts are of local provenance. Xenoliths in the dacite porphyry suggest that the northern tip of the Antarctic Peninsula is underlain by a metamorphic complex composed of amphibolites, meta-tonalites and pelitic gneiss containing garnet, sillimanite, cordierite, hercynite, and andalucite. Such rocks are not known in the Scotia metamorphic complex, nor in the Trinity Peninsula Group and its low grade metamorphic derivatives, which also occur as rare xenoliths in the dacite. Previous dating of xenoliths collected from the moraines suggested a late Carboniferous age for this amphibolite-grade metamorphism. Both the Jurassic-Cenozoic magmatic arc of the Antarctic Peninsula and the accretionary complex rocks of the Trinity Peninsula Group were thus developed, at least in part, over pre-existing continental crust.

scholarly journals Eoalpine (Cretaceous) very low- to low-grade metamorphism recorded on the illite-muscovite-rich fraction of metasediments from South Tisia (eastern Mt Papuk, Croatia)

2010 ◽  
Vol 61 (6) ◽  
pp. 469-481 ◽  
Author(s):  
Vanja Biševac ◽  
Kadosa Balogh ◽  
Dražen Balen ◽  
Darko Tibljaš
Keyword(s):  
Pannonian Basin ◽  
Regional Metamorphism ◽  
Eastern Alps ◽  
Low Grade ◽  
Metamorphic Complex ◽  
Grade Metamorphism ◽  
Sedimentary Sequences ◽  
Surrounding Areas ◽  
Temperature Time ◽  
Good Agreement

Eoalpine (Cretaceous) very low- to low-grade metamorphism recorded on the illite-muscovite-rich fraction of metasediments from South Tisia (eastern Mt Papuk, Croatia)Eoalpine very low- to low-grade metamorphism related to Cretaceous orogenesis has been investigated in the Slavonian Mts, Croatia. Samples belonging to the Psunj metamorphic complex (PMC), the Radlovac metamorphic complex (RMC) and Permian-Triassic and Triassic sedimentary sequences (PTSS) were studied. The Kübler and Árkai indices of all the analysed samples indicate high-anchizonal to epizonal metamorphism. The degree of Eoalpine metamorphism tends to be constant in all samples implying that the different complexes passed through and recorded the same event. Measurements of illite-white K-micab0-parameter of the RMC samples imply transitional low- to medium-pressure character of the metamorphism. These data together with K-Ar ages (~100-80 Ma) measured on illite-white K-mica rich < 2 μm grain-size fractions point to Late Cretaceous very low- to low-grade regional metamorphism presumably related to the main nappe-forming compressional events in the Pannonian Basin and the Carpathians. The P-T-t (pressure-temperature-time) evolution of the studied area is in good agreement with similar scenarios in the surrounding areas of Tisia, but also in Eastern Alps, Carpathians and Pannonian Basin (ALCAPA).

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