High pressure, halogen-bearing melt in ultra-high temperature felsic granulites of the Central Maine Terrane, Connecticut (US)

2021 ◽  
Author(s):  
Silvio Ferrero ◽  
Jay J. Ague ◽  
Patrick J. O'Brien ◽  
Bernd Wunder ◽  
Laurent Remusat ◽  
...  
Keyword(s):  
High Pressure ◽  
Melt Inclusions ◽  
Extreme Temperature ◽  
Crustal Thickening ◽  
Deep Roots ◽  
Crustal Rocks ◽  
Melting Temperatures ◽  
Peak Metamorphism ◽  
Partial Melts ◽  
Relative Rarity

<p>Inclusions of relic high pressure melts provide information on the fate of crustal rocks in the deep roots of orogens during collision and crustal thickening, including at extreme temperature conditions exceeding 1000°C. However, discoveries of high pressure melt inclusions are still a relative rarity among case studies of inclusions in metamorphic minerals. Here we present the results of experimental and microchemical investigations of nanogranitoids in garnets from the felsic granulites of the Central Maine Terrane (Connecticut, US). Their successful experimental re-homogenization at ~2 GPa confirms that they originally were trapped portions of deep melts and makes them the first direct evidence of high pressure during peak metamorphism and melting for these felsic granulites. The trapped melt has a hydrous, granitic, and peraluminous character typical of crustal melts from metapelites. This melt is higher in mafic components (FeO and MgO) than most of the nanogranitoids investigated previously, likely the result of the extreme melting temperatures – well above 1000°C. This is the first natural evidence of the positive correlation between temperature and mafic character of the melt, a trend previously supported only by experimental evidence. Moreover, it poses a severe caveat against the common assumption that partial melts from metasediments at depth are always leucogranitic in composition. NanoSIMS measurement on re-homogenized inclusions show significant amounts of CO<sub>2</sub>, Cl and F. Halogen abundance in the melt is considered to be a proxy for the presence of brines (strongly saline fluids) at depth. Brines are known to shift the melting temperatures of the system toward higher values, and may have been responsible for delaying melt production via biotite dehydration melting until these rocks reached extreme temperatures of more than 1000°C, rather than 800-850°C as commonly observed for these reactions.</p>

scholarly journals Late orogenic extension in Hellenides

2001 ◽  
Vol 34 (1) ◽  
pp. 149
Author(s):  
Α. ΚΙΛΙΑΣ
Keyword(s):  
High Pressure ◽  
Accretionary Prism ◽  
Crustal Thickening ◽  
Plate Boundaries ◽  
Accretionary Wedge ◽  
Northern Greece ◽  
Crustal Rocks ◽  
Crete Island ◽  
Late Orogenic Extension ◽  
Back Arc

In the Hellenic orogen both typs of late orogenic extension, associated with deep crustal parts exhumation, are recognized during the Tertiare: In the areas of Olympos-Ossa and Pelion Mts in Northern Greece, as well as in the island of Crete in Southern Greece a bivergent late orogenic extension is recognized. Nappes collapse took place immediately above the cold accretionary wedge while compression was active at depth. Heer high pressure assemplages were good preserved. On the contrary, in the Rhodope and Cyclades areas an asymmetric extension dominates. Heer extensional exhumation of deep crustal rocks took place in the high thermal flow back-arc region and high pressure metamorphic rocks were highly overprinted by greenschist to amphibolite facies metamorphism. Partial melting and granitoids intrusions followed the high grade metamorphic reworking of the rocks. Tertiary late orogenic extension in the Hellenides tooke place simultaneously with successive subductions processes and crustal thickening at the front of the extended plate, forming with the associated compression a SW-ward migrated system. Extension started in the Rhodope massif during the Eocene/Oligocene to be reached in the Olympos, Ossa, Pilion and Cyclades areas in the Oligocene/Miocene and final in the Crete island at the more external Hellenides, during the Mid-Miocene. Changes in the rate of convergence between Africa and Eurasia associated with retreating plate boundaries conditions allowed the successive, extensional exhumation of the deep crustal rocks in the Hellenides. Assymetric collapse in the back-arc area was possibly favoured, because the high potential energy of the thickened crust in the active orogenic arc was counteracted by the continuing subduction along the boundaries of the converging segments of Africa and Eurasia. Symmetric collapse of the overthickened crust above the cold accretionary prism was favoured probably, due to an increasing of the upward pressure produced by the unterplating of the lithospheric slap beneath the accretionary wedge.

Magmatic evolution of the Gaussberg lamproite (Antarctica): volatile content and glass composition

2004 ◽  
Vol 68 (1) ◽  
pp. 83-100 ◽  
Author(s):  
E. Salvioli-Mariani ◽  
L. Toscani ◽  
D. Bersani
Keyword(s):  
High Pressure ◽  
Infrared Spectra ◽  
Melt Inclusions ◽  
Glass Composition ◽  
Relative Increase ◽  
The Other ◽  
Residual Liquid ◽  
Volatile Content ◽  
Magmatic Evolution ◽  
Ultrapotassic Rock

AbstractThe lamproite of Gaussberg is an ultrapotassic rock where leucite, olivine and clinopyroxene microphenocrysts occur in a glass-rich groundmass, containing microliths of leucite, clinopyroxene, apatite, phlogopite and rare K-richterite.Abundant silicate melt inclusions occur in olivine, leucite and, rarely, in clinopyroxene microphenocrysts. Raman investigations on melt inclusions showed the presence of pure CO2 in the shrinkage bubbles. On the other hand, the glass of the groundmass is CO2-poor and contains up to 0.70 wt.% of dissolved H2O, as estimated by infrared spectra. It is inferred that CO2 was released at every stage of evolution of the lamproite magma (CO2-rich shrinkage bubbles), whereas H2O was retained for longer in the liquid. At Gaussberg, CO2 seems to have a major role at relatively high pressure where it favoured the crystallization of H2O-poor microphenocrysts; the uprise of the magma to the surface decreased the solubility of CO2 and caused a relative increase in water activity. As a consequence, phlogopite and K-richterite appeared in the groundmass.The glass composition of both the groundmass and melt inclusions suggests different evolutions for the residual liquids of the investigated samples. Sample G886 shows the typical evolution of a lamproite magma, where the residual liquid evolves toward peralkaline and Na-rich composition and crystallizes K-richterite in the latest stage. Sample G895 derives from mixing/mingling of different batches of magma; effectively glasses from melt inclusions in leucite and clinopyroxene are more alkaline than those found in early crystallized olivine. Leucite and clinopyroxene crystallized early from a relatively more alkaline batch of lamproite magma and, successively, a less alkaline, olivinebearing magma batch assimilated them during its rise to the surface.

Timing of Paleoproterozoic granitoid magmatism along the northwestern Superior Province margin: implications for the tectonic evolution of the Thompson Nickel BeltThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 325-346 ◽  
Author(s):  
N. Machado ◽  
L. M. Heaman ◽  
T. E. Krogh ◽  
W. Weber ◽  
M. T. Corkery
Keyword(s):  
Sensu Stricto ◽  
Crustal Thickening ◽  
Superior Province ◽  
Granitoid Magmatism ◽  
Continental Block ◽  
Granitic Magmatism ◽  
Peak Metamorphism ◽  
Granite Magmatism ◽  
Superior Craton ◽  
Superior Margin

The U–Pb geochronology of three granitoid plutons and three granitic pegmatite dykes, largely from the Thompson Nickel Belt located along the northwestern Superior craton margin, was investigated to place constraints on the timing of felsic magmatism associated with closure of the Manikewan Ocean and final continent–continent collision to form the Trans-Hudson Orogen. These data indicate that 1840–1820 Ma granite magmatism along the Superior margin was more active than previously thought and that some magmatism extended beyond the Thompson Nickel Belt sensu stricto, including the 1836 ± 3 Ma Mystery Lake granodiorite, 1822 ± 5 Ma Wintering Lake granodiorite, and the 1825 ± 8 Ma Fox Lake granite located in the Split Lake Block. Granitic pegmatites within the Thompson Nickel Belt were emplaced late in the collisional history in the period 1.79–1.75 Ga and include a 1770 ± 2 Ma dyke exposed at the Thompson pit, a 1767 ± 6 Ma dyke at the Pipe Pit, and a 1786 ± 2 Ma dyke located at Paint Lake. The final stage of crustal amalgamation in the eastern Trans-Hudson Orogen involved Superior Province crustal thickening and partial melting forming 1.84–1.82 Ga granite magmas and then final collision at ∼1.8 Ga between the Superior Province and a continental block to the west consisting of the previously amalgamated Sask and Hearne cratons. Heating of the Superior craton margin and granitic magmatism continued past peak metamorphism (1790–1750 Ma); this thermal event is represented by the emplacement of numerous late pegmatite dykes and evidenced by cooling dates recorded by metamorphic minerals (e.g., titanite) in reworked Archean gneisses and Proterozoic intrusions.

Gel-setting and Gel-melting Temperatures of Aqueous Gelatin Solutions under High Pressure Measured by a Hot-wire Method

1996 ◽  
Vol 60 (8) ◽  
pp. 1349-1350 ◽  
Author(s):  
Keiko Shimada ◽  
Yoshio Sakai ◽  
Kazuyuki Nagamatsu ◽  
Tomoshige Hori ◽  
Rikimaru Hayashi
Keyword(s):  
High Pressure ◽  
Hot Wire ◽  
Melting Temperatures ◽  
Wire Method

scholarly journals Deep roots for mid-ocean-ridge volcanoes revealed by plagioclase-hosted melt inclusions

Nature ◽  
2019 ◽  
Vol 572 (7768) ◽  
pp. 235-239 ◽  
Author(s):  
Emma N. Bennett ◽  
Frances E. Jenner ◽  
Marc-Alban Millet ◽  
Katharine V. Cashman ◽  
C. Johan Lissenberg
Keyword(s):  
Melt Inclusions ◽  
Deep Roots ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans−North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
Guochun Zhao ◽  
Changqing Yin ◽  
Jiahui Qian ◽  
...  
Keyword(s):  
Shear Zone ◽  
North China ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Slip Systems ◽  
High Grade ◽  
Ductile Shear Zone ◽  
Crustal Rocks ◽  
Ductile Shear ◽  
Lower Crustal

In worldwide orogenic belts, crustal-scale ductile shear zones are important tectonic channels along which the orogenic root (i.e., high-grade metamorphic lower-crustal rocks) commonly experienced a relatively quick exhumation or uplift process. However, their tectonic nature and geodynamic processes are poorly constrained. In the Trans−North China orogen, the crustal-scale Zhujiafang ductile shear zone represents a major tectonic boundary separating the upper and lower crusts of the orogen. Its tectonic nature, structural features, and timing provide vital information into understanding this issue. Detailed field observations showed that the Zhujiafang ductile shear zone experienced polyphase deformation. Variable macro- and microscopic kinematic indicators are extensively preserved in the highly sheared tonalite-trondhjemite-granodiorite (TTG) and supracrustal rock assemblages and indicate an obvious dextral strike-slip and dip-slip sense of shear. Electron backscattered diffraction (EBSD) was utilized to further determine the crystallographic preferred orientation (CPO) of typical rock-forming minerals, including hornblende, quartz, and feldspar. EBSD results indicate that the hornblendes are characterized by (100) <001> and (110) <001> slip systems, whereas quartz grains are dominated by prism <a> and prism <c> slip systems, suggesting an approximate shear condition of 650−700 °C. This result is consistent with traditional thermobarometry pressure-temperature calculations implemented on the same mineral assemblages. Combined with previously reported metamorphic data in the Trans−North China orogen, we suggest that the Zhujiafang supracrustal rocks were initially buried down to ∼30 km depth, where high differential stress triggered the large-scale ductile shear between the upper and lower crusts. The high-grade lower-crustal rocks were consequently exhumed upwards along the shear zone, synchronous with extensive isothermal decompression metamorphism. The timing of peak collision-related crustal thickening was further constrained by the ca. 1930 Ma metamorphic zircon ages, whereas a subsequent exhumation event was manifested by ca. 1860 Ma syntectonic granitic veins and the available Ar-Ar ages of the region. The Zhujiafang ductile shear zone thus essentially record an integrated geodynamic process of initial collision, crustal thickening, and exhumation involved in formation of the Trans−North China orogen at 1.9−1.8 Ga.

scholarly journals The fate of planetary cores in giant and ice-giant planets

2019 ◽  
Vol 631 ◽  
pp. L4 ◽  
Author(s):  
S. Mazevet ◽  
R. Musella ◽  
F. Guyot
Keyword(s):  
High Pressure ◽  
Ab Initio ◽  
Inner Core ◽  
Giant Planets ◽  
Ab Initio Molecular Dynamics ◽  
Solid Core ◽  
Potential Core ◽  
Melting Temperatures ◽  
The Core ◽  
Pressure Melting

Context. The Juno probe that currently orbits Jupiter measures its gravitational moments with great accuracy. Preliminary results suggest that the core of the planet may be eroded. While great attention has been paid to the material properties of elements constituting the envelope, little is known about those that constitute the core. This situation clutters our interpretation the Juno data and modeling of giant planets and exoplanets in general. Aims. We calculate the high-pressure melting temperatures of three potential components of the cores of giant planets, water, iron, and a simple silicate, MgSiO3, to investigate the state of the deep inner core. Methods. We used ab initio molecular dynamics simulations to calculate the high-pressure melting temperatures of the three potential core components. The planetary adiabats were obtained by solving the hydrostatic equations in a three-layer model adjusted to reproduce the measured gravitational moments. Recently developed ab initio equations of state were used for the envelope and the core. Results. We find that the cores of the giant and ice-giant planets of the solar system differ because the pressure–temperature conditions encountered in each object correspond to different regions of the phase diagrams. For Jupiter and Saturn, the results are compatible with a diffuse core and mixing of a significant fraction of metallic elements in the envelope, leading to a convective and/or a double-diffusion regime. We also find that their solid cores vary in nature and size throughout the lifetimes of these planets. The solid cores of the two giant planets are not primordial and nucleate and grow as the planets cool. We estimate that the solid core of Jupiter is 3 Gyr old and that of Saturn is 1.5 Gyr old. The situation is less extreme for Uranus and Neptune, whose cores are only partially melted. Conclusions. To model Jupiter, the time evolution of the interior structure of the giant planets and exoplanets in general, their luminosity, and the evolution of the tidal effects over their lifetimes, the core should be considered as crystallizing and growing rather than gradually mixing into the envelope due to the solubility of its components.

Late Triassic orogenic assembly of the Tibetan Plateau: constraints from magmatism and metamorphism in the east Lhasa terrane

2021 ◽  
Author(s):  
Yanfei Chen ◽  
Zeming Zhang ◽  
Richard M Palin ◽  
Zuolin Tian ◽  
Hua Xiang ◽  
...  
Keyword(s):  
Crustal Thickening ◽  
Late Triassic ◽  
The Tibetan Plateau ◽  
Plate Convergence ◽  
Lhasa Terrane ◽  
The North ◽  
Tectonic History ◽  
Peak Metamorphism ◽  
Tethys Ocean ◽  
Lower Crustal

Abstract The early Mesozoic evolution of the Lhasa terrane, which represents a major component of the Himalayan-Tibetan orogen, remains highly controversial. In particular, geological units and events documented either side of the eastern Himalayan syntaxis (EHS) are poorly correlated. Here, we report new petrological, geochemical and geochronological data for co-genetic peraluminous S-type granites and metamorphic rocks (gneiss and schist) from the Motuo–Bomi–Chayu region of the eastern Lhasa terrane, located on the eastern flank of the EHS. Zircon U–Pb dating indicates that these units record both Late Triassic magmatic (216–206 Ma) and metamorphic (209–198 Ma) episodes. The granites were derived from a Paleoproterozoic crustal source with negative zircon εHf(t) values (–5.5 to –16.6) and TDM2 model ages of 1.51–1.99 Ga, and are interpreted to have formed by crustal anatexis of nearby metasediments during collisional orogeny and crustal thickening. The gneisses and schists experienced similar upper amphibolite-facies peak metamorphism and associated partial melting, followed by decompressional cooling and retrograde metamorphism. These rocks were buried to lower-crustal depths and then exhumated to the surface in a collisional orogenic setting during plate convergence. From comparison of these data to other metamorphic belts with similar grades and ages, and association of coeval granitic magmatism widespread in the central-east Lhasa terrane, we propose that the studied co-genetic magmatism and metamorphism in the Motuo–Bomi–Chayu region records Late Triassic accretion of the North Lhasa and South Lhasa terranes, which represents the first evidence of the Paleo-Tethys ocean (PTO) closure in this part of Asia. These data provide new constraints on the spatial and temporal evolution of the Paleo-Tethyan Wilson Cycle and provide a ‘missing link’ to correlate the geology and tectonic history of the Lhasa terrane continental crust on either side of the EHS.

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