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Talc is a common mineral in some metamorphic rocks. It is a sheet silicate which means that it is structurally similar to micas and clay minerals. This mineral is always an alteration product, it forms at the expense of other preexisting minerals. The alteration reactions that produce talc are metamorphic — they took place at elevated ...
Thermodynamic calculations demonstrate that talc is stable in H2O‐undersaturated parts of the mantle wedge where its stability is controlled by the pressure‐dependent, fluid‐absent reaction ...
High-grade metamorphism takes place at temperatures greater than 320 o C and relatively high pressure. As grade of metamorphism increases, hydrous minerals become less hydrous, by ... which gives the rock a greasy feel, similar to that of soap. Talc is an Mg-rich mineral, and thus soapstones from ultrabasic igneous protoliths, like peridotites ...
On further heating, antigorite-bearing mineral assemblages break down to talc, chlorite, olivine and pyroxene at temperature from 550°C at low P to 650–680°C to higher pressure (Bromiley & Pawley, 2003; Schwartz et al., 2013; Ulmer & Trommsdorff, 1995; Wunder & Schreyer, 1997). Antigorite is the serpentine polymorph stable at HP–UHP ...
The thermal conductivity and thermal diffusivity of talc have been measured over a range of temperature (298–1,373 K) and pressure (0.5–3.0 GPa) conditions using the transient plane-source method.The results show that both the thermal conductivity and thermal diffusivity are dependent upon the prevailing temperature and pressure …
The transition occurs within the thermodynamic stability of talc and is observed in both triclinic and monoclinic polymorphs. It is a rather unique behavior and is likely related to the reported polytypic transition between the low-pressure polytype talc-I to the high-pressure polytype talc-II (Scott et al., 2007, Gleason et al., 2008).
The hydrothermal metamorphism results in alteration to such Mg-Fe rich hydrous minerals as talc, chlorite, serpentine, actinolite, tremolite, zeolites, and clay minerals. ... These ultrahigh pressures can produce minerals that are only stable at very high pressure, such as the SiO 2 polymorphs coesite and stishovite. In addition they can ...
Talc schist sample 1013 also has high Ti, P and Nb contents and is slightly depleted in Cr and Ni relative to the serpentinite, indicating it may also contain a small mafic component. ... Spandler C, Hermann J (2006) High-pressure veins in eclogite from New Caledonia and their significance for fluid migration and seismic activity in subduction ...
This polytypic transition occurs at ∼3 GPa, which is within the thermodynamic stability field of talc. The transition could be a structural precursor of the 10-Å phase, a …
The pressure-temperature conditions of the reactions governing the high-pressure stability of talc were investigated in experiments on the bulk composition Mg 3 …
Abstract. We present high-pressure infrared spectra of two geologically important hydrous minerals: talc, Mg 3 Si 4 O 10 (OH) 2 and lawsonite, CaAl 2 Si 2 O 7 (OH)2·H 2 O,·at room temperature. For lawsonite, our data span the far infrared region from 150 to 550 cm −1 and extend to 25 GPa. We combine our new spectroscopic data with ...
Talc is known to be one of the weakest minerals, making it potentially important for the deformation dynamics and seismic characteristics of faults. However, little is known about talc's mechanical properties at high temperatures under confining …
The thermal conductivity of talc at high pressures and temperatures is therefore valuable in the design of high-pressure experiments and apparatus. In this paper measurements of the thermal conductivity of fired and unfired talk are presented. Measurements were made at pressures ranging from 0 to 2.5 GPa and temperatures from 150 to 900 K.
Talc is a hydrous magnesium rich layered silicate that is widely disseminated in the Earth from the seafloor to over 100 km depth, in ultra-high pressure metamorphism of oceanic crust.
The talc-kyanite association is therefore of special interest as an indicator of a high-pressure metamorphic environ-ment. The yoderite-bearing talc-kyanite-quartz schist from Mautia Hill ...
High-pressure measurements are in good agreement with DFT calculations for talc and lizardite. Pressure-induced displacive modifications are identified in …
High‐Pressure Mechanical Properties of Talc: Implications for Fault Strength and Slip Processes. The hydrous mineral talc is stable over a relatively large P‐T field and can …
The pressure-temperature conditions of the reactions governing the high-pressure stability of talc were investigated in experiments on the bulk composition Mg3Si4O10(OH)2 + H2O at 2.9-6.8 GPa, 650 ...
Here we measured the kinetics of antigorite dehydration in situ at high pressure and high temperature by time-resolved synchrotron X-ray diffraction in a closed system. ... Chollet et al. previously showed that the dehydration of talc was reversible in this assembly, demonstrating the presence of free water in a similar Ti-Au capsule. The whole ...
66, and several off-diagonal components show anomalous pressure dependence. This non-monotonic pressure dependence of elastic constant components is likely related to the structural changes and is often manifested in a polytypic transition from a low-pressure polytype talc-I to a high-pressure polytype talc-II.
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Therefore, the seismic anisotropy of polycrystalline talc was also calculated at a high pressure (P = 29 kbars) using the elastic properties of single crystal talc at the given pressure (Supplementary Fig. S2 and S4). The seismic anisotropies of polycrystalline talc showed low but still large seismic anisotropies of the P- and S-waves (AVp = 38 ...
High-pressure high-volume suction may lead to air stealing, hypoxaemia or the perpetuation of air leaks.104 Likewise, ... Surgical chemical pleurodesis is best achieved by using 5 g sterile graded talc, with which the …
Talc can form in high-pressure ultramafic rocks that have been enriched in SiO 2 through the reaction with silica-bearing aqueous fluids (Manning, 1995, 1997). Based on geophysical data, a ∼4 km thick layer of altered ultramafic rock enriched in talc was inferred to be present at the slab-mantle interface in the central Mexican subduction ...
Whiteschists appear in numerous high- and ultrahigh-pressure rock suites and are characterized by the mineral assemblage kyanite + talc (+-quartz or coesite). We demonstrate that whiteschist mineral assemblages are well stable up to pressures of more than 4 GPa but may already form at pressures of 0.5 GPa. The formation of whiteschists …
Recently, Gatta et al. reinvestigated the crystal structure of the 1Tc (or 1A) polytype of talc by single-crystal X-ray and neutron diffraction and its high-pressure behaviour by in situ single-crystal X-ray diffraction up to 16 GPa, providing also a critical review of the elastic behaviour of talc on the basis of the data previously reported.
We report new results of high‐pressure conductivity measurements on talc at 1.0–4.0 GPa and up to 1293 K. We found a sharp conductivity increase above the dehydration temperature,
The high-pressure stability of talc and 10 Å phase: potential storage sites for H2O in subduction zones. Am. Miner. 80, 998–1003 (1995). Article ADS CAS Google Scholar ...
There is currently little information available about the thermal and physical properties of talc during or after dehydration. We reported new results using pulse-heating method and found that both the thermal conductivity and thermal diffusivity are dependent upon the prevailing temperature and pressure conditions to a certain extent.
High blood pressure affects a large share of the global adult population. Previous studies suggest probiotics may help prevent hypertension. New findings point …
Talc may be the cause of the high geothermal gradient in the hot subduction zone. Key Points. A novel pulse heater was designed for use in high pressures …
In the system K2O-MgO-Al2O3-SiO2-H2O (KMASH) the high-temperature and low-pressure stability limits for the assemblage talc + phengite have been investigated by reversed experiments at pressures ...
talc-I to a high-pressure polytype talc-II. The polytypic transition of talc occurs at pressures within its thermodynamic stability. However, the bulk and shear elastic moduli show no …
The partial derivative has been dropped because in the approximations of the model Θ D does not vary with T at constant V.By the Debye theory there is a characteristic variation of specific heat with temperature specified by the ratio T/Θ D (Fig. 1), and comparison of Eqs. (1.6), (2.20) shows this ratio to be constant on an adiabat. The …