If a subducting plate consists of a weak buoyant layer atop a stronger negatively buoyant layer, the former will detach at the depth where the buoyancy force exceeds slab pull, and extrude upward as a semi-coherent sheet. This type of delamination and stacking was proposed to explain exhumation of UHP rocks in the Dora Maira massif in Piedmont , Italy,  in the Dabie orogen,  and in the Himalaya. A variant of this mechanism, in which the exhuming material undergoes folding, but not wholescale disruption, was suggested for the Dabie orogen,where exhumation-related stretching lineations and gradients in metamorphic pressure indicate rotation of the exhuming block; .
The buoyancy of a microcontinent locally slows the rollback of and steepens the dip of subducting mafic lithosphere.
This model was developed to explain repeated cycles of subduction and exhumation documented in the Aegean and Calabria—Apennine orogens. UHP exhumation by slab rollback has not yet been extensively explored numerically, but it has been reproduced in numerical experiments of Apennine-style collisions. If continental material is subducted within a confined channel, the material tends to undergo circulation driven by tractions along the base of the channel and the relative buoyancy of rocks inside the channel;  the flow can be complex, generating nappe-like or chaotically mixed bodies.
Buoyancy alone is unlikely to drive exhumation of UHP rocks to Earth's surface, except in oceanic subduction zones. Studies of numerical geodynamics suggest that both subducted sediment and crystalline rocks may rise through the mantle wedge diapirically to form UHP terranes. Foundering of the gravitationally unstable portions of continental lithosphere locally carries quartzofeldspathic rocks into the mantle  and may be ongoing beneath the Pamir. From Wikipedia, the free encyclopedia. Regional metamorphism at extreme conditions: Implications for orogeny at convergent plate margins.
Journal of Asian Earth Sciences, v. Geological Survey Professional Paper, v. Hatcher, J. Terra Nova. Lithos , v. DOI: Continental subduction channel processes: Plate interface interaction during continental collision. Chinese Science Bulletin 58, Ascent of the ultrahigh-pressure Western Gneiss Region, Norway. In Cloos, M. Metamorphic petrology. Ultra-high-pressure metamorphism Ultra-high-temperature metamorphism.
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Categories : Metamorphic petrology. Very recent advances in determination of melting relations of mantle and core materials with laser-heating techniques are beginning to provide accurate constraints Shen and Heinz, Chapter Sometimes lost in the debate on melting curves is the fact that a decade ago, there simply were no data for most Earth materials, only guesses and at best approximate models. Moreover, it is now possible to carry out in situ melting studies on multi-component systems, including natural assemblages, to deep mantle conditions.
These results address whether or not partial melting is responsible for the observed seismic anomalies at the base of the mantle and provide constraints for mantle convection models Chapter 7. The composition, structure, formation, evolution, and current dynamic state of the Earth's core is an area of tremendous excitement Chapter 8.
The keys to understanding the available geophysical data are the material properties of liquid and crystalline iron under core conditions. New synchrotron-based methods and new developments in theory are being applied to determine all of the pertinent physical properties, and in conjunction with seismological and geodynamic data, to develop a full understanding of the core and its interactions with the mantle Chapter 7.
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There has been considerable progress in determining the melting and phase relations of iron into the megabar range with new techniques Chapter Constraints are also obtained from theory Chapter These results feed into geophysical models for the outer and inner core flow, structural state, evolution, and the geodynamo. Moreover, there is remarkable evidence that the Earth's inner core rotates at a different rate than the rest of the Earth.
This evidence in turn rests on the observation that the inner core is elastically anisotropic, a subject of current experimental and theoretical study from the standpoint of mineral physics, as described above. Whole Earth processes must be grounded in accurate thermodynamic descriptions of phase equilibria in multi-component systems, as discussed by Navrotsky Chapter New developments in this area include increasingly accurate equations of state Duffy and Wang, Chapter 14 required for modeling of phase equilibria as well as for direct comparison with seismic density profiles through the planet.
Recent developments in in situ vibrational spectroscopy and theoretical models provide a means for independently testing available thermochemical data and a means for extending those data to high pressures and temperatures Gillet et aI. Accurate determinations of crystal structures provide a basis for understanding thermochemical trends Chapter 9. Systematics for understanding solid-solution behavior and element partitioning are now available, at least to the uppermost regions of the lower mantle Fei, Chapter New measurements for dense hydrous phases are beginning to provide answers to fundamental questions regarding their stability of hydrous phases in the mantle Chapters 3 and 9 and the partitioning of hydrogen and oxygen between the mantle and core Chapter 8.
One of the key recent findings in high-pressure research is the remarkable effect of pressure on the chemistry of the elements, at conditions ranging from deep metamorphism of crustal minerals Chapter 2 to "contact metamorphism" at the core-mantle boundary Chapter 7. Pressure-induced changes in Earth materials represent forefront problems in condensed-matter physics. New crystal structures appear and the chemistry of volatiles changes Chapter 9.
Pressure-induced electronic transitions and magnetic collapse in transition metal ions strongly affect mineral properties and partitioning of major, minor, and trace elements Chapter Evidence for these transitions from experiment Chapter 18 and theory Chapter 19 is important for developing models for Earth formation and chemical differentiation. The conventional view of structurally and chemically complex minerals of the crust giving way to simple, close-packed structures of the deep mantle and a simple iron core is being replaced by a new chemical picture wherein dense silicates, oxides, and metals exhibit unusual electronic and magnetic properties and chemistry.
In the end, this framework must dovetail with seismological observations indicating an interior of considerable regional variability, both radially and laterally depending on depth e. Chapters 6 and 7. Information concerning the chemical and physical properties of Earth materials at high pressures and temperatures is being integrated with geophysical and geochemical data to create a more comprehensive global view of the state, processes, and history of the Earth. In particular, models of the Earth's interior are being developed that reflect the details contained in the seismic record but are bounded by laboratory information on the physics and chemistry of the constituent materials.
Such "Reference Earth Models" includes the development of reference data sets and modeling codes. Tools that produce seismological profiles from hypothesized mineralogies Chapters 4 and 5 are now possible, as are tools for testing these models against 'reference' seismological data sets Chapter 6.
These models incorporate the known properties of the Earth, such as crust and lithosphere structure, and thus have both an Earth-materials and seismological orientation. The Earth cannot be understood without considering the rest of the solar system. The terrestrial planets of our solar system share a common origin, and our understanding of the formation of the Earth is tied to our understanding of the formation of its terrestrial neighbors, particularly with respect to evaluating the roles of homogeneous and heterogeneous processes during accretion.
As a result of recent developments in space exploration, as well as in the scope of future planetary missions, we have new geophysical and geochemical data for the other terrestrial planets. Models for the accretion history of the Earth can now be reevaluated in relation to this new data.
Experiments on known Earth materials provide the thermodynamic data necessary to calculate the high-pressure mineralogy of model compositions for the interior of Mars and Venus. Notably, the outer planets have the same volatile components as the Earth, just different abundances. Studies of the outer planets provide both an additional perspective on our own planet as well as a vast area of opportunity for application of these newly developed experimental techniques Chapter 1 and The utility of synchrotron radiation techniques in mineralogy has exceeded the expectations of even the most optimistic.
New spectroscopic methods developed for high-pressure mineralogy are now available for characterizing small samples from other types of experiments. For example, the same techniques developed for in situ studies at high pressures and temperatures are being used to investigate microscopic inclusions such as coesite in high-pressure metamorphic rocks Chapter 2 and deep-mantle samples as inclusions in diamond Chapter 3.
Institute of Geosciences
With the availability of a new generation of synchrotron radiation sources Chapter 1 and spectroscopic techniques Chapter 17 , a systematic application of new methods, including micro tomographic x-ray analysis of whole rock samples, is now becoming routinely possible. Contributions in technology. Finally, there are implications beyond the geosciences. Mineralogy has historically has led many to conceptual and technical developments used in other fields, including metallurgy and materials science, and the new area of ultrahigh pressure mineralogy continues this tradition.
As pointed out in Chapter 1, many highpressure techniques have their origins in geoscience laboratories, and in many respects, geoscience leads development of high-pressure techniques in physics, chemistry, and materials science.
New developments include the application of synthetic diamond for new classes of 'large-volume' high-pressure cells. Interestingly, information on diamond stability, including its metastable growth, feeds back directly on efforts to grow large diamonds for the next generation of such high-pressure devices Chapter 1. Microanalytical techniques, such as micro-spectroscopy and x-ray diffraction, developed for high-pressure research are now used outside of this field of research as well.
Ultrahigh pressure metamorphism (Book, ) [gitepost.tk]
The study of minerals and mineral analogs under pressure is leading to new materials. As in the synthesis of diamond itself, these same scientific approaches promise the development of novel, technological materials. Russell J. Chapter 1. Hemley, p. Chapter 2. High-pressure minerals from deeply subducted metamorphic rocks by J.
Liou, R. Zhang, W. Chapter 3. Schmidt, p. Chapter 4. McDonough and Roberta L. Rudnick, p. Chapter 5. Agee, p.
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