TY  - JOUR
A1  - Nicoli, Gautier
A1  - Ferrero, Silvio
T1  - Nanorocks, volatiles and plate tectonics
JF  - Geoscience frontiers
N2  - The global geological volatile cycle (H, C, N) plays an important role in the long term self-regulation of the Earth system. However, the complex interaction between its deep, solid Earth components (i.e. crust and mantle), Earth's fluid envelopes (i.e. atmosphere and hydrosphere) and plate tectonic processes is a subject of ongoing debate. In this study we want to draw attention to how the presence of primary melt (MI) and fluid (FI) inclusions in high-grade metamorphic minerals could help constrain the crustal component of the volatile cycle. To that end, we review the distribution of MI and FI throughout Earth's history, from ca. 3.0 Ga ago up to the present day. We argue that the lower crust might constitute an important, long-term, volatile storage unit, capable to influence the composition of the surface envelopes through the mean of weathering, crustal thickening, partial melting and crustal assimilation during volcanic activity. Combined with thermodynamic modelling, our compilation indicates that periods of well-established plate tectonic regimes at <0.85 Ga and 1.7-2.1 Ga, might be more prone to the reworking of supracrustal lithologies and the storage of volatiles in the lower crust. Such hypothesis has implication beyond the scope of metamorphic petrology as it potentially links geodynamic mechanisms to habitable surface conditions. MI and FI in metamorphic crustal rocks then represent an invaluable archive to assess and quantify the co-joint evolution of plate tectonics and Earth's external processes. (C) 2021 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
KW  - Nanorocks
KW  - Plate tectonics
KW  - Volatiles
KW  - Lower crust
Y1  - 2021
U6  - https://doi.org/10.1016/j.gsf.2021.101188
SN  - 1674-9871
VL  - 12
IS  - 5
PB  - Amsterdam [u.a.]
CY  - Elsevier
ER  - 
TY  - JOUR
A1  - Lanari, Pierre
A1  - Ferrero, Silvio
A1  - Goncalves, Philippe
A1  - Grosch, Eugene G.
T1  - Metamorphic geology
BT  - progress and perspectives
JF  - Geological Society
Y1  - 2019
SN  - 978-1-78620-400-4
U6  - https://doi.org/10.1144/SP478-2018-186
SN  - 0305-8719
SN  - 2041-4927
VL  - 478
SP  - 1
EP  - 12
PB  - Geological Society
CY  - London
ER  - 
TY  - JOUR
A1  - Ghignone, Stefano
A1  - Sudo, Masafumi
A1  - Balestro, Gianni
A1  - Borghi, Alessandro
A1  - Gattiglio, Marco
A1  - Ferrero, Silvio
A1  - Schijndel, Valby van
T1  - Timing of exhumation of meta-ophiolite units in the Western Alps
BT  - New tectonic implications from Ar-40/Ar-39 white mica ages from Piedmont Zone (Susa Valley)
JF  - Lithos : an international journal of mineralogy, petrology, and geochemistry
N2  - A multidisciplinary approach to the study of collisional orogenic belts can improve our knowledge of their geodynamic evolution and may suggest new tectonic models, especially for (U)HP rocks inside the accretionary wedge. In the Western Alps, wherein nappes of different origin are stacked, having recorded different metamorphic peaks at different stages of the orogenic evolution. This study focuses on the External (EPZ) and Internal (IPZ) ophiolitic units of the Piedmont Zone (Susa Valley, Western Alps), which were deformed throughout four tectonometamorphic phases (D1 to D4), developing different foliations and cleavages (S1 to S4) at different metamorphic conditions. The IPZ and EPZ are separated by a shear zone (i.e. the Susa Shear Zone (SSZ)) during which a related mylonitic foliation (SM) developed. S1 developed at high pressure conditions (Epidote-eclogite vs. Lawsonite-blueschist facies conditions for IPZ and EPZ, respectively), as suggested by the composition of white mica (i.e. phengite), whereas S2 developed at low pressure conditions (Epidote-greenschist facies conditions in both IPZ and EPZ) and is defined by muscovite. White mica defining the SM mylonitic foliation (T1) is mostly defined by phengite, while the T2-related disjunctive cleavage is defined by fine-grained muscovite. The relative chronology inferred from meso-and micro-structural observations suggests that T1 was near-coeval with respect to the D2, while T2 developed during D4. A new set of radiometric ages of the main metamorphic foliations were obtained by in situ Ar/Ar dating on white mica. Different generations of white mica defining S1 and S2 foliations in both the IPZ and EPZ and SM in the SSZ, were dated and two main groups of ages were obtained. In both IPZ and EPZ, S1 foliation developed at-46-41 Ma, while S2 foliation developed at-40-36 Ma and was nearly coeval with the SM mylonitic foliation (-39-36 Ma). Comparison between structural, petrological and geochronological data allows to define time of coupling of the different units and consequently to infer new tectonic implications for the exhumation of meta-ophiolites of the Piedmont Zone within axial sector of the Western Alps.
KW  - Exhumation
KW  - meta-ophiolites
KW  - Piedmont Zone
KW  - Western Alps
KW  - Ar-40
KW  - Ar-39
Y1  - 2021
U6  - https://doi.org/10.1016/j.lithos.2021.106443
SN  - 0024-4937
SN  - 1872-6143
VL  - 404-405
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Ziemann, Martin Andreas
A1  - Angel, Ross J.
A1  - Wunder, Bernd
T1  - Kumdykolite, kokchetavite, and cristobalite crystallized in nanogranites from felsic granulites, Orlica-Snieznik Dome (Bohemian Massif): not evidence for ultrahigh-pressure conditions
JF  - Contributions to mineralogy and petrology
N2  - A unique assemblage including kumdykolite and kokchetavite, polymorphs of albite and K-feldspar, respectively, together with cristobalite, micas, and calcite has been identified in high-pressure granulites of the Orlica-Snieznik dome (Bohemian Massif) as the product of partial melt crystallization in preserved nanogranites. Previous reports of both kumdykolite and kokchetavite in natural rocks are mainly from samples that passed through the diamond stability field. However, because the maximum pressure recorded in these host rocks is <3 GPa, our observations indicate that high pressure is not required for the formation of kumdykolite and kokchetavite, and their presence is not therefore an indicator of ultrahigh-pressure conditions. Detailed microstructural and microchemical investigation of these inclusions indicates that such phases should instead be regarded as (1) a direct mineralogical criteria to identify former melt inclusions with preserved original compositions, including H2O and CO2 contents and (2) indicators of rapid cooling of the host rocks. Thus, the present study provides novel criteria for the interpretation of melt inclusions in natural rocks and allows a more rigorous characterization of partial melts during deep subduction to mantle depth as well as their behavior on exhumation.
KW  - Partial melt
KW  - Polymorphs
KW  - Deep fluids
KW  - Nanogranites
KW  - Kumdykolite
KW  - Kokchetavite
KW  - Cristobalite
Y1  - 2016
U6  - https://doi.org/10.1007/s00410-015-1220-x
SN  - 0010-7999
SN  - 1432-0967
VL  - 171
SP  - 61
EP  - 65
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Wunder, Bernd
A1  - Ziemann, Martin Andreas
A1  - Waelle, Markus
T1  - Carbonatitic and granitic melts produced under conditions of primary
immiscibility during anatexis in the lower crust
JF  - Earth & planetary science letters
N2  - Carbonatites are peculiar magmatic rocks with mantle-related genesis, commonly interpreted as the products of melting of CO2-bearing peridotites, or resulting from the chemical evolution of mantle derived magmas, either through extreme "differentiation or secondary immiscibility. Here we report the first finding of anatectic carbonatites of crustal origin, preserved as calcite-rich polycrystalline inclusions in garnet from low-to-medium pressure migmatites of the Oberpfalz area, SW Bohemian Massif (Central Europe). These inclusions originally trapped a melt of calciocarbonatitic composition with a characteristic enrichment in Ba, Sr and LREE. This interpretation is supported by the results of a detailed microstructural and microchemical investigation, as well as re-melting experiments using a piston cylinder apparatus. Carbonatitic inclusions coexist in the same cluster with crystallized silicate melt inclusions (nanogranites) and COH fluid inclusions, suggesting conditions of primary immiscibility between two melts and a fluid during anatexis. The production of both carbonatitic and granitic melts during the same anatectic event requires a suitable heterogeneous protolith. This may be represented by a sedimentary sequence containing marble lenses of limited extension, similar to the one still visible in the adjacent central Moldanubian Zone. The presence of CO2-rich fluid inclusions suggests furthermore that high CO2 activity during anatexis may be required to stabilize a carbonate-rich melt in a silica-dominated, system. This natural occurrence displays a remarkable similarity with experiments on carbonate-silicate melt immiscibility, where CO2 saturation is a condition commonly imposed. In conclusion, this study shows how the investigation of partial melting through melt inclusion studies may unveil unexpected processes whose evidence, while preserved in stiff minerals such as garnet, is completely obliterated in the rest of the rock due to metamorphic re-equilibration. Our results thus provide invaluable new insights into the processes which shape the geochemical evolution of our planet, such as the redistribution of carbon and strategic metals during orogenesis. (C) 2016 Elsevier B.V. All rights reserved.
KW  - partial melting
KW  - carbonatites
KW  - nanogranites
KW  - garnet
KW  - melt inclusions;
 nanocarbonatites
Y1  - 2016
U6  - https://doi.org/10.1016/j.epsl.2016.08.043
SN  - 0012-821X
SN  - 1385-013X
VL  - 454
SP  - 121
EP  - 131
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Wunder, Bernd
A1  - Walczak, Katarzyna
A1  - Ziemann, Martin Andreas
T1  - Preserved near ultrahigh-pressure melt from continental crust subducted to mantle depths
JF  - Geology
N2  - Remnants of hydrous melt formed at mantle depths have been identified and characterized within high-pressure leucogranulites of the Orlica-Snieznik Dome (Bohemian Massif, central Europe). They occur as nanogranites in garnet formed via partial melting of granitoids during the Variscan orogeny. Melt composition and H2O content have been investigated in situ after experimental re-homogenization of the nanogranites, and are consistent with melts produced experimentally from crustal lithologies at mantle depths. This is the first geochemical study of melt inclusions from natural crustal rocks equilibrated close to the stability field of coesite, shedding light on how continental crust melts during deep subduction. Whereas decompressional melting is commonly invoked for deeply subducted crustal lithologies, melting occurred near or at the metamorphic peak pressure in the Orlica-Snieznik granulites. Melting of deeply subducted crustal rocks significantly modifies the rheology and thus promotes fast exhumation: this process has a critical influence on the geodynamic evolution of subduction-collision orogens as well as crustal differentiation at depth.
Y1  - 2015
U6  - https://doi.org/10.1130/G36534.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 43
IS  - 5
SP  - 447
EP  - 450
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Godard, Gaston
A1  - Palmeri, Rosaria
A1  - Wunder, Bernd
A1  - Cesare, Bernardo
T1  - Partial melting of ultramafic granulites from Dronning Maud Land, Antarctica
BT  - constraints from melt inclusions and thermodynamic modeling
JF  - American mineralogist : an international journal of earth and planetary materials
N2  - In the Pan-African belt of the Dronning Maud Land, Antarctica, crystallized melt inclusions (nanogranitoids) occur in garnet from ultramafic granulites. The granulites contain the peak assemblage pargasite+garnet+clinopyroxene with rare relict orthopyroxene and biotite, and retrograde symplectites at contacts between garnet and amphibole. Garnet contains two generations of melt inclusions. Type 1 inclusions, interpreted as primary, are isolated, < 10 mu m in size, and generally have negative crystal shapes. They contain kokchetavite, kumdykolite, and phlogopite, with quartz and zoisite as minor phases, and undevitrified glass was identified in one inclusion. Type 2 inclusions are < 30 mu m in size, secondary, and contain amphibole, feldspars, and zoisite. Type 2 inclusions appear to be the crystallization products of a melt that coexisted with an immiscible CO2-rich fluid. The nanogranitoids were re-homogenized after heating in a piston-cylinder in a series of four experiments to investigate their composition. The conditions ranged between 900 and 950 degrees C at 1.5-2.4 GPa. Type 1 inclusions are trachytic and ultrapotassic, whereas type 2 melts are dacitic to rhyolitic. Thermodynamic modeling of the ultramafic composition in the MnNCKFMASHTO system shows that anatexis occurred at the end of the prograde P-T path, between the solidus (at ca. 860 degrees C-1.4 GPa) and the peak conditions (at ca. 960 degrees C-1.7 GPa). The model melt composition is felsic and similar to that of type 1 inclusions, particularly when the melting degree is low (< 1 mol%), close to the solidus. However the modeling fails to reproduce the highly potassic signature of the melt and its low H2O content. The combination of petrology, melt inclusion study, and thermodynamic modeling supports the interpretation that melt was produced by anatexis of the ultramafic boudins near peak P-T conditions, and that type 1 inclusions contain the anatectic melt that was present during garnet growth. The felsic, ultrapotassic composition of the primary anatectic melts is compatible with low melting degrees in the presence of biotite and amphibole as reactants.
KW  - Nanogranitoids
KW  - partial melting
KW  - thermodynamic modeling
KW  - Antarctica
KW  - ultramafic granulites
KW  - kumdykolite
KW  - kokchetavite
KW  - High-Grade Metamorphism
KW  - Anatexis
KW  - and Granite Magmatism
Y1  - 2018
U6  - https://doi.org/10.2138/am-2018-6214
SN  - 0003-004X
SN  - 1945-3027
VL  - 103
IS  - 4
SP  - 610
EP  - 622
PB  - Mineralogical Society of America
CY  - Chantilly
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Braga, R.
A1  - Berkesi, M.
A1  - Cesare, Bernardo
A1  - Ouazaa, N. Laridhi
T1  - Production of metaluminous melt during fluid-present anatexis: an example from the Maghrebian basement, La Galite Archipelago, central Mediterranean
JF  - Journal of metamorphic geology
N2  - Garnet brought to the surface by late Miocene granitoids at La Galite Archipelago (Central Mediterranean, Tunisia) contains abundant primary melt and fluid inclusions. Microstructural observations and mineral chemistry define the host garnet as a peritectic phase produced by biotite incongruent melting at ~800 degrees C and 0.5GPa, under fluid-present conditions. The trapped melt is leucogranitic with an unexpected metaluminous and almost peralkaline character. Fluid inclusions are one phase at room temperature, and contain a CO2-dominated fluid, with minor H2O, N-2 and CH4. Siderite and an OH-bearing phase were identified by Raman and IR spectroscopy within every analysed inclusion, and are interpreted as products of a post-entrapment carbonation/hydration reaction between the fluid and the host during cooling. The fluid present during anatexis is therefore inferred to have been originally richer in both H2O and CO2. The production of anatectic melt with a metaluminous signature can be explained as the result of partial melting of relatively Al-poor protoliths assisted by CO2-rich fluids.
KW  - fluid inclusions
KW  - garnet
KW  - anatexis
KW  - nanogranites
KW  - melt inclusions
Y1  - 2014
U6  - https://doi.org/10.1111/jmg.12068
SN  - 0263-4929
SN  - 1525-1314
VL  - 32
IS  - 2
SP  - 209
EP  - 225
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Borghini, Alessia
A1  - Wunder, Bernd
A1  - Walle, Markus
A1  - Günter, Christina
A1  - Ziemann, Martin Andreas
T1  - A treasure chest full of nanogranitoids
BT  - an archive to investigate crustal melting in the Bohemian Massif
JF  - Metamorphic Geology: Microscale to Mountain Belts
N2  - The central European Bohemian Massif has undergone over two centuries of scientific investigation which has made it a pivotal area for the development and testing of modern geological theories. The discovery of melt inclusions in high-grade rocks, either crystallized as nanogranitoids or as glassy inclusions, prompted the re-evaluation of the area with an ‘inclusionist’ eye. Melt inclusions have been identified in a wide range of rocks, including felsic/perpotassic granulites, migmatites, eclogites and garnet clinopyroxenites, all the result of melting events albeit over a wide range of pressure/temperature conditions (800–1000°C/0.5–5 GPa). This contribution provides an overview of such inclusions and discusses the qualitative and quantitative constraints they provide for melting processes, and the nature of melts and fluids involved in these processes. In particular, data on trace-element signatures of melt inclusions trapped at mantle depths are presented and discussed. Moreover, experimental re-homogenization of nanogranitoids provided microstructural criteria allowing assessment of the conditions at which melt and host are mutually stable during melting. Overall this work aims to provide guidelines and suggestions for petrologists wishing to explore the fascinating field of melt inclusions in metamorphic terranes worldwide, based on the newest discoveries from the still-enigmatic Bohemian Massif.
Y1  - 2018
SN  - 978-1-78620-400-4
U6  - https://doi.org/10.1144/SP478.19
SN  - 0305-8719
VL  - 478
SP  - 13
EP  - 38
PB  - Geological Soc Publishing House
CY  - Bath
ER  - 
TY  - JOUR
A1  - Ferrero, Silvio
A1  - Angel, Ross J.
T1  - Micropetrology
BT  - Are Inclusions Grains of Truth?
JF  - Journal of petrology
N2  - Inclusions in minerals, whether fluids, melts or crystalline phases, are small pieces of the large-scale puzzle of Nature, time-consuming to investigate and often of difficult interpretation. Yet they are windows into the past of their host mineral. Mineral inclusions provide the opportunity to unravel the genesis of their host, and the increasingly refined understanding of their elastic behaviour provides the basis for alternative, equilibrium-independent geobarometry. Fluid and melt inclusions reveal information about material transfer in the Earth system, from shallow mineralization to mantle re-fertilization via subduction. The study of inclusions is thus one of the most intriguing and fertile branches of micropetrology. In this contribution, we focus on two recent developments: the use of elasticity models to extract the formation conditions of the host crystal, and the discovery and investigation of melt inclusions in metamorphic rocks. We also discuss how to evaluate the information provided by inclusions, given that they are no longer at the pressure and temperature conditions of entrapment. We discuss how to understand and quantify the changes undergone during cooling and depressurization, and how metastability-related phenomena in inclusions, such as crystallization of rare polymorphs and preservation of the original content of volatiles in fluid and melt inclusions, provide direct evidence that inclusions represent closed systems. The field of study of inclusions in minerals still has a largely untapped potential. The most fruitful avenues for future research will emerge from continuous technological innovation in analytical and imaging techniques, the application of experimental petrology, and the development and application of new theoretical models for coupled mineral behaviour under changing P-T conditions.
KW  - inclusions
KW  - nanogranitoids
KW  - polymorphs
KW  - elastic geobarometry
Y1  - 2018
U6  - https://doi.org/10.1093/petrology/egy075
SN  - 0022-3530
SN  - 1460-2415
VL  - 59
IS  - 9
SP  - 1671
EP  - 1700
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Carvalho, Bruna B.
A1  - Bartoli, Omar
A1  - Ferri, Fabio
A1  - Cesare, Bernardo
A1  - Ferrero, Silvio
A1  - Remusat, Laurent
A1  - Capizzi, Luca Samuele
A1  - Poli, Stefano
T1  - Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)
JF  - Journal of metamorphic geology
N2  - We investigate the inclusions hosted in peritectic garnet from metapelitic migmatites of the Kinzigite Formation (Ivrea Zone, NW Italy) to evaluate the starting composition of the anatectic melt and fluid regime during anatexis throughout the upper amphibolite facies, transition, and granulite facies zones. Inclusions have negative crystal shapes, sizes from 2 to 10 mu m and are regularly distributed in the core of the garnet. Microstructural and micro-Raman investigations indicate the presence of two types of inclusions: crystallized silicate melt inclusions (i.e., nanogranitoids, NI), and fluid inclusions (FI). Microstructural evidence suggests that FI and NI coexist in the same cluster and are primary (i.e., were trapped simultaneously during garnet growth). FI have similar compositions in the three zones and comprise variable proportions of CO2, CH4, and N-2, commonly with siderite, pyrophyllite, and kaolinite, suggesting a COHN composition of the trapped fluid. The mineral assemblage in the NI contains K-feldspar, plagioclase, quartz, biotite, muscovite, chlorite, graphite and, rarely, calcite. Polymorphs such as kumdykolite, cristobalite, tridymite, and less commonly kokchetavite, were also found. Rehomogenized NI from the different zones show that all the melts are leucogranitic but have slightly different compositions. In samples from the upper amphibolite facies, melts are less mafic (FeO + MgO = 2.0-3.4 wt%), contain 860-1700 ppm CO2 and reach the highest H2O contents (6.5-10 wt%). In the transition zone melts have intermediate H2O (4.8-8.5 wt%), CO2 (457-1534 ppm) and maficity (FeO + MgO = 2.3-3.9 wt%). In contrast, melts at granulite facies reach highest CaO, FeO + MgO (3.2-4.7 wt%), and CO2 (up to 2,400 ppm), with H2O contents comparable (5.4-8.3 wt%) to the other two zones. Our results represent the first clear evidence for carbonic fluid-present melting in the Ivrea Zone. Anatexis of metapelites occurred through muscovite and biotite breakdown melting in the presence of a COH fluid, in a situation of fluid-melt immiscibility. The fluid is assumed to have been internally derived, produced initially by devolatilization of hydrous silicates in the graphitic protolith, then as a result of oxidation of carbon by consumption of Fe3+-bearing biotite during melting. Variations in the compositions of the melts are interpreted to result from higher T of melting. The H2O contents of the melts throughout the three zones are higher than usually assumed for initial H2O contents of anatectic melts. The CO2 contents are highest at granulite facies, and show that carbon-contents of crustal magmas are not negligible at high T. The activity of H2O of the fluid dissolved in granitic melts decreases with increasing metamorphic grade. Carbonic fluid-present melting of the deep continental crust represents, together with hydrate-breakdown melting reactions, an important process in the origin of crustal anatectic granitoids.
KW  - anatexis
KW  - fluid inclusions
KW  - fluid regime
KW  - Ivrea Zone
KW  - melt inclusions
Y1  - 2019
U6  - https://doi.org/10.1111/jmg.12463
SN  - 0263-4929
SN  - 1525-1314
VL  - 37
IS  - 7
SP  - 951
EP  - 975
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Borghini, Alessia
A1  - Ferrero, Silvio
A1  - Wunder, Bernd
A1  - Laurent, Oscar
A1  - Ziemann, Martin Andreas
T1  - Granitoid melt inclusions in orogenic peridotite and the origin of garnet clinopyroxenite
JF  - Geology
N2  - Granitic melt inclusions were found in layers of garnet clinopyroxenites from orogenic peridotites hosted in high-pressure felsic granulites of the Granulitgebirge, central Europe. The inclusions are both glassy and crystallized, and occur as clusters in the garnet. Microstructural features suggest that the inclusions formed while garnet was growing as a peritectic phase, likely alongside clinopyroxene. The chemistry of the melt, in particular its trace element signature, shows a crustal contribution, probably due to the involvement of phengite in the melt-producing reaction, most likely in the presence of a fluid. The presence of a granitoid melt in mantle rocks may be the result of localized melting of a phengite-bearing protolith either already present in the peridotites or, more likely, within the local deeply subducted crustal units. In the latter case, the melt would have infiltrated the peridotites and generated pyroxenite via metasomatism. In either case, the presence of granitoid inclusions in orogenic peridotite provides direct evidence for a genetic connection between a high-pressure crustal melt and garnet pyroxenites. The in situ characterization of these remnants of natural melt provides direct quantitative constraints on (one of) the agents responsible for the interaction between crust and mantle.
Y1  - 2018
U6  - https://doi.org/10.1130/G45316.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 46
IS  - 11
SP  - 1007
EP  - 1010
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Borghini, Alessia
A1  - Ferrero, Silvio
A1  - O’Brien, Patrick J.
A1  - Laurent, Oscar
A1  - Günter, Christina
A1  - Ziemann, Martin Andreas
T1  - Cryptic metasomatic agent measured in situ in Variscan mantle rocks
BT  - Melt inclusions in garnet of eclogite, Granulitgebirge, Germany
N2  - Garnet of eclogite (formerly termed garnet clinopyroxenite) hosted in lenses of orogenic garnet peridotite from the Granulitgebirge, NW Bohemian Massif, contains unique inclusions of granitic melt, now either glassy or crystallized. Analysed glasses and re‐homogenized inclusions are hydrous, peraluminous, and enriched in highly incompatible elements characteristic of the continental crust such as Cs, Li, B, Pb, Rb, Th, and U. The original melt thus represents a pristine, chemically evolved metasomatic agent, which infiltrated the mantle via deep continental subduction during the Variscan orogeny. The bulk chemical composition of the studied eclogites is similar to that of Fe‐rich basalt and the enrichment in LILE and U suggest a subduction‐related component. All these geochemical features confirm metasomatism. In comparison with many other garnet+clinopyroxene‐bearing lenses in peridotites of the Bohemian Massif, the studied samples from Rubinberg and Klatschmühle are more akin to eclogite than pyroxenites, as reflected in high jadeite content in clinopyroxene, relatively low Mg, Cr, and Ni but relatively high Ti. However, trace elements of both bulk rock and individual mineral phases show also important differences making these samples rather unique. Metasomatism involving a melt requiring a trace element pattern very similar to the composition reported here has been suggested for the source region of rocks of the so‐called durbachite suite, that is, ultrapotassic melanosyenites, which are found throughout the high‐grade Variscan basement. Moreover, the Th, U, Pb, Nb, Ta, and Ti patterns of these newly studied melt inclusions (MI) strongly resemble those observed for peridotite and its enclosed pyroxenite from the T‐7 borehole (Staré, České Středhoři Mountains) in N Bohemia. This suggests that a similar kind of crustal‐derived melt also occurred here. This study of granitic MI in eclogites from peridotites has provided the first direct characterization of a preserved metasomatic melt, possibly responsible for the metasomatism of several parts of the mantle in the Variscides.
KW  - clinopyroxenite
KW  - eclogite
KW  - melt inclusions
KW  - metasomatism
KW  - orogenic peridotite
Y1  - 2019
U6  - https://doi.org/10.1111/jmg.12519
SN  - 1525-1314
SN  - 0263-4929
VL  - 38
SP  - 207
EP  - 234
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  - 
TY  - JOUR
A1  - Berkesi, Marta
A1  - Czuppon, Gyorgy
A1  - Szabo, Csaba
A1  - Kovacs, Istvan
A1  - Ferrero, Silvio
A1  - Boiron, Marie-Christine
A1  - Peiffert, Chantal
T1  - Pargasite in fluid inclusions of mantle xenoliths from northeast Australia (Mt. Quincan)
BT  - evidence of interaction with asthenospheric fluid
JF  - Chemical geology : official journal of the European Association for Geochemistry
N2  - Three spinel lherzolite xenoliths from Mt. Quincan (Queensland, northeastern Australia) were studied with special attention to their enclosed fluid inclusions. The xenoliths are deformed, have porphyroclastic textures and overall show very similar petrographic features. The only significant difference is manifested in the abundance of fluid inclusions in the samples, mostly in orthopyroxene porphyroclasts. Xenolith JMTQ11 is fluid inclusion-free, whereas xenolith JMTQ20 shows a high abundance of fluid inclusions (fluid inclusion-rich). Xenolith JMTQ45 represents a transitional state between the previous two, as it contains only a small amount of fluid inclusions (fluid inclusion-bearing). Previous studies revealed that these xenoliths and the entrapped fluid inclusions represent a former addition of a MORB-type fluid to the pre-existing lithosphere, resulting from asthenosphere upwelling. There is a progressive enrichment in LREE, Nb, Sr and Ti from the fluid inclusion-free xenolith through the fluid inclusion-bearing one to the fluid inclusion-rich lherzolite. This suggests an increase in the extent of the interaction between the fluid-rich melt and the lherzolite wallrock. In addition, the same interaction is considered to be responsible for the formation of pargasitic amphibole as well. The presence of fluid inclusions indicates fluid migration at mantle depth, and their association with exsolution lamellae in orthopyroxene suggests fluid entrapment following the continental rifting (thermal relaxation) during cooling. A series of analyses, including microthermometry coupled with Raman spectroscopy, FTIR hyperspectral imaging, and Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) was carried out on the fluid inclusions. Based on the results, the entrapped high-density fluid is composed of 7589 mol% CO2, 918 mol% H2O, 0.11.7 mol% N-2 and <= 0.5 mol% H2S with dissolved trace elements (melt component). Our findings suggest that the metasomatic fluid phase could have been either a fluid/fluid-rich silicate melt released from the deeper asthenosphere, or a coexisting incipient fluid-rich silicate melt. Further cooling, possibly due to thermal relaxation and the upward migration of the fluid phase, caused the investigated lherzolites to reach pargasite stability conditions. We conclude that pargasite, even if only present in very limited modal proportions, can be a common phase at spinel lherzolite stability in the lithospheric upper mantle in continental rift back-arc settings. Studies of fluid inclusions indicate that significant CO2 release from the asthenosphere in a continental rifting environment is resulting from asthenosphere upwelling and its addition to the lithospheric mantle together with fluid-rich melt lherzolite interaction that leaves a CO2-rich fluid behind.
KW  - Fluid inclusions
KW  - Pargasite
KW  - Asthenospheric fluid
KW  - Metasomatism
KW  - Mt. Quincan
KW  - Australia
Y1  - 2018
U6  - https://doi.org/10.1016/j.chemgeo.2018.06.022
SN  - 0009-2541
SN  - 1872-6836
VL  - 508
SP  - 182
EP  - 196
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bartoli, Omar
A1  - Acosta-Vigil, Antonio
A1  - Ferrero, Silvio
A1  - Cesare, Bernardo
T1  - Granitoid magmas preserved as melt inclusions in high-grade metamorphic rocks
JF  - American mineralogist : an international journal of earth and planetary materials
N2  - This review presents a compositional database of primary anatectic granitoid magmas, entirely based on melt inclusions (MI) in high-grade metamorphic rocks. Although MI are well known to igneous petrologists and have been extensively studied in intrusive and extrusive rocks, MI in crustal rocks that have undergone anatexis (migmatites and granulites) are a novel subject of research. They are generally trapped along the heating path by peritectic phases produced by incongruent melting reactions. Primary MI in high-grade metamorphic rocks are small, commonly 5-10 pm in diameter, and their most common mineral host is peritectic garnet. In most cases inclusions have crystallized into a cryptocrystalline aggregate and contain a granitoid phase assemblage (nanogranitoid inclusions) with quartz, K-feldspar, plagioclase, and one or two mica depending on the particular circumstances. After their experimental remelting under high-confining pressure, nanogranitoid MI can be analyzed combining several techniques (EMP, LA-ICP-MS, NanoSIMS, Raman). The trapped melt is granitic and metaluminous to peraluminous, and sometimes granodioritic, tonalitic, and trondhjemitic in composition, in agreement with the different P-T-a(H2o) conditions of melting and protolith composition, and overlap the composition of experimental glasses produced at similar conditions. Being trapped along the up-temperature trajectory as opposed to classic MI in igneous rocks formed during down-temperature magma crystallization fundamental information provided by nanogranitoid MI is the pristine composition of the natural primary anatectic melt for the specific rock under investigation. So far similar to 600 nanogranitoid MI, coming from several occurrences from different geologic and geodynamic settings and ages, have been characterized. Although the compiled MI database should be expanded to other potential sources of crustal magmas, MI data collected so far can be already used as natural "starting-point" compositions to track the processes involved in formation and evolution of granitoid magmas.
KW  - Granitoid magmas
KW  - melt inclusions
KW  - nanogranite
KW  - crustal anatexis
KW  - peritectic phase
Y1  - 2016
U6  - https://doi.org/10.2138/am-2016-5541CCBYNCND
SN  - 0003-004X
SN  - 1945-3027
VL  - 101
SP  - 1543
EP  - 1559
PB  - Mineralogical Society of America
CY  - Chantilly
ER  -