One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina

Finch, Melanie; Weinberg, Roberto Ferrez; Fuentes, María Gabriela; Hasalová, Pavlína; Becchio, Raúl

doi:10.1016/j.jsg.2015.01.002

Cited by 24 publications

(34 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Deformation recorded is dominantly, marked by ductile shear zones developed during the Ordovician (Büttner et al., ; Finch, Weinberg, Fuentes, Hasalová, & Becchio, ; Hippertt & Hongn, ; Hongn, Mon, Cuevas, & Tubia, ). Emplacement of granite plutons derived from anatexis occurred largely between 480 and 460 Ma along with high‐grade metamorphism and associated with N–S and NW–SE shear zones (Bahlburg, Berndt, & Gerdes, ; Büttner et al., ; Finch et al., ). However, the precise age relationships between magmatism, metamorphism and deformation are not well known (Hongn & Becchio, ; Hongn et al., ).…”

Section: Regional Settingmentioning

confidence: 99%

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling

Sola

Hasalová

Weinberg

et al. 2017

Journal Metamorphic Geology

View full text Add to dashboard Cite

Water‐fluxed melting has long been thought to have a minor influence on the thermal and chemical structure of the crust. We report here on amphibolite facies metasedimentary rocks from the 490–450 Ma Famatinian Orogen, in northwest Argentina, that have undergone water‐fluxed incongruent biotite melting at relatively low temperature, which have produced and lost a significant volume of melt. The protoliths consist of the turbiditic Puncoviscana Formation (Neoproterozoic to Early Cambrian). The field area exhibits a condensed metamorphic field gradient, from greenschist to amphibolite facies suprasolidus conditions, recording a low pressure almost isobaric path, reaching peak conditions estimated at 700°C at 4 kbar. Thermodynamic modelling in the MnNCKFMASHTO system is applied to investigate melting at such low pressure as a function of water content. Calculations using a typical turbidite composition show how small amounts of added free H2O may increase significantly the melt fraction with little or no change in either the melt or residual phase compositions. They indicate negligible difference in normative An–Ab–Or proportions and ferromagnesian contents between melts derived by dehydration and water‐fluxed melts. The same is true for the content of H2O dissolved in melts, which remains constant and the melt produced is granitic whether or not aqueous fluids are present. Thus, neither the residue nor the melt composition are indicators of the presence of aqueous fluids during anatexis. Recognizing the impact of small additions of H2O to an anatectic terrane may therefore be difficult. The most significant change related to water‐fluxing is the relative proportions of minerals and melt fraction, rather than the actual mineral assemblage. The modal proportion of feldspar decreased while those of cordierite and biotite increased in the residual assemblages, as <5 mol.% of free H2O was added. The impact of this addition is to more than double the proportion of water‐undersaturated melt to 25–30 mol.%. We have also developed a simple way to estimate how much melt a residual rock has lost, if the compositional trends of the protoliths are known. In summary, we find that even though the addition of small amounts of free H2O impacts significantly on rock fertility, there is little obvious record in the field. The combined application of careful petrological investigation and thermodynamic modelling is the key to identify the influence of aqueous fluids, and exploit systems that became open not only to fluid influx but also to the extraction of melt.

show abstract

Section: Regional Settingmentioning

confidence: 99%

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling

Sola

Hasalová

Weinberg

et al. 2017

Journal Metamorphic Geology

View full text Add to dashboard Cite

show abstract

“…6 in Büttner, 2009 with stereonets in Fig. 2 of Finch et al, 2015). From (a) and (b) we conclude movement continuity through time and space and suggested that movement on the PSZ remained constant as it cooled.…”

mentioning

confidence: 64%

“…6 in Büttner, 2009 with stereonets in Fig. 2 of Finch et al, 2015). Our lack of a precise age of movement on the PSZ should not detract from the message that the Famatinian orogeny recorded in Sierra de Quilmes was a result of crustal shortening rather than crustal extension.…”

mentioning

confidence: 79%

“…In Finch et al (2015) we contend that the shear zones of the Tolomb on complex are part of the same shortening event that formed the PSZ. We came to that conclusion by combining the following observations: a) W-directed movement in high-grade regions was contemporaneous with partial melting, to judge from the relationships between leucosomes and thrust planes and folds (Fig.…”

mentioning

confidence: 95%

“…We came to that conclusion by combining the following observations: a) W-directed movement in high-grade regions was contemporaneous with partial melting, to judge from the relationships between leucosomes and thrust planes and folds (Fig. 4d,e in Finch et al, 2015 and4c in Büttner et al, 2005). b) W-directed movement in high-grade and low-grade rocks alike in the Divisadero region is the same as in the mylonitic rocks of PSZ (compare Fig.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Reply to comment by S.H. Büttner on: “One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina”

Finch

Weinberg

Fuentes

et al. 2015

Journal of Structural Geology

Self Cite

View full text Add to dashboard Cite

The Pre-Andean Phases of Construction of the Southern Andes Basement in Neoproterozoic–Paleozoic Times

Heredia

Garcı́a-Sansegundo

Gallastegui

et al. 2018

Springer Earth System Sciences

View full text Add to dashboard Cite

During the late Neoproterozoic and Paleozoic times, the Southern Andes of Argentina and Chile (21º-55º S) formed part of the southwestern margin of Gondwana. During this period of time, a set of continental fragments of variable extent and allochtony was successively accreted to that margin, resulting in six Paleozoic orogenies of different temporal and spatial extension: Pampean (Ediacaran-early Cambrian), Famatinian (Middle Ordovician-Silurian), Ocloyic (Middle Ordovician-Devonian), Chanic (Middle Devonian-early Carboniferous), Gondwanan (Middle Devonian-middle Permian) and Tabarin (late Permian-Triassic). All these orogenies culminate with collisional events, with the exception of the Tabarin and a part of the Gondwanan orogenies that are subduction-related.

show abstract

One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina

Cited by 24 publications

References 87 publications

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling

Reply to comment by S.H. Büttner on: “One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina”

The Pre-Andean Phases of Construction of the Southern Andes Basement in Neoproterozoic–Paleozoic Times

Contact Info

Product

Resources

About

One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina

Cited by 24 publications

References 87 publications

Low‐P melting of metapelitic rocks and the role of H2O: Insights from phase equilibria modelling

Low‐P melting of metapelitic rocks and the role of H2O: Insights from phase equilibria modelling

Reply to comment by S.H. Büttner on: “One kilometre-thick ultramylonite, Sierra de Quilmes, Sierras Pampeanas, NW Argentina”

The Pre-Andean Phases of Construction of the Southern Andes Basement in Neoproterozoic–Paleozoic Times

Contact Info

Product

Resources

About

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling

Low‐P melting of metapelitic rocks and the role of H₂O: Insights from phase equilibria modelling