A review of the geologic history of the Himalayan-Tibetan orogen suggests that at least 1400 km of north-south shortening has been absorbed by the orogen since the onset of the Indo-Asian collision at about 70 Ma. Significant crustal shortening, which leads to eventual construction of the Cenozoic Tibetan plateau, began more or less synchronously in the Eocene (50–40 Ma) in the Tethyan Himalaya in the south, and in the Kunlun Shan and the Qilian Shan some 1000–1400 km in the north. The Paleozoic and Mesozoic tectonic histories in the Himalayan-Tibetan orogen exerted a strong control over the Cenozoic strain history and strain distribution. The presence of widespread Triassic flysch complex in the Songpan-Ganzi-Hoh Xil and the Qiangtang terranes can be spatially correlated with Cenozoic volcanism and thrusting in central Tibet. The marked difference in seismic properties of the crust and the upper mantle between southern and central Tibet is a manifestation of both Mesozoic and Cenozoic tectonics. The form...

Geologic Evolution of the Himalayan-Tibetan Orogen

The thermodynamic properties of 154 mineral end-members, 13 silicate liquid end-members and 22 aqueous fluid species are presented in a revised and updated data set. The use of a temperature-dependent thermal expansion and bulk modulus, and the use of high-pressure equations of state for solids and fluids, allows calculation of mineral–fluid equilibria to 100 kbar pressure or higher. A pressure-dependent Landau model for order–disorder permits extension of disordering transitions to high pressures, and, in particular, allows the alpha–beta quartz transition to be handled more satisfactorily. Several melt end-members have been included to enable calculation of simple phase equilibria and as a first stage in developing melt mixing models in NCKFMASH. The simple aqueous species density model has been extended to enable speciation calculations and mineral solubility determination involving minerals and aqueous species at high temperatures and pressures. The data set has also been improved by incorporation of many new phase equilibrium constraints, calorimetric studies and new measurements of molar volume, thermal expansion and compressibility. This has led to a significant improvement in the level of agreement with the available experimental phase equilibria, and to greater flexibility in calculation of complex mineral equilibria. It is also shown that there is very good agreement between the data set and the most recent available calorimetric data.

An internally consistent thermodynamic data set for phases of petrological interest

Two end member models of how the high elevations in Tibet formed are (i) continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and (ii) time-dependent, localized shear between coherent lithospheric blocks. Recent studies of Cenozoic deformation, magmatism, and seismic structure lend support to the latter. Since India collided with Asia ∼55 million years ago, the rise of the high Tibetan plateau likely occurred in three main steps, by successive growth and uplift of 300- to 500-kilometer-wide crustal thrust-wedges. The crust thickened, while the mantle, decoupled beneath gently dipping shear zones, did not. Sediment infilling, bathtub-like, of dammed intermontane basins formed flat high plains at each step. The existence of magmatic belts younging northward implies that slabs of Asian mantle subducted one after another under ranges north of the Himalayas. Subduction was oblique and accompanied by extrusion along the left lateral strike-slip faults that slice Tibet's east side. These mechanisms, akin to plate tectonics hidden by thickening crust, with slip-partitioning, account for the dominant growth of the Tibet Plateau toward the east and northeast.

http://science.sciencemag.org/content/sci/294/5547/1671.full.pdf

Oblique Stepwise Rise and Growth of the Tibet Plateau

The thermodynamic properties of 254 end-members, including 210 mineral end-members, 18 silicate liquid end-members and 26 aqueous fluid species are presented in a revised and updated internally consistent thermodynamic data set. The PVT properties of the data set phases are now based on a modified Tait equation of state (EOS) for the solids and the Pitzer & Sterner (1995) equation for gaseous components. Thermal expansion and compressibility are linked within the modified Tait EOS (TEOS) by a thermal pressure formulation using an Einstein temperature to model the temperature dependence of both the thermal expansion and bulk modulus in a consistent way. The new EOS has led to improved fitting of the phase equilibrium experiments. Many new end-members have been added, including several deep mantle phases and, for the first time, sulphur-bearing minerals. Silicate liquid end-members are in good agreement with both phase equilibrium experiments and measured heat of melting. The new dataset considerably enhances the capabilities for thermodynamic calculation on rocks, melts and aqueous fluids under crustal to deep mantle conditions. Implementations are already available in thermocalc to take advantage of the new data set and its methodologies, as illustrated by example calculations on sapphirine-bearing equilibria, sulphur-bearing equilibria and calculations to 300 kbar and 2000 °C to extend to lower mantle conditions.

An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids

[1] The HiRISE camera features a 0.5 m diameter primary mirror, 12 m effective focal length, and a focal plane system that can acquire images containing up to 28 Gb (gigabits) of data in as little as 6 seconds. HiRISE will provide detailed images (0.25 to 1.3 m/pixel) covering ∼1% of the Martian surface during the 2-year Primary Science Phase (PSP) beginning November 2006. Most images will include color data covering 20% of the potential field of view. A top priority is to acquire ∼1000 stereo pairs and apply precision geometric corrections to enable topographic measurements to better than 25 cm vertical precision. We expect to return more than 12 Tb of HiRISE data during the 2-year PSP, and use pixel binning, conversion from 14 to 8 bit values, and a lossless compression system to increase coverage. HiRISE images are acquired via 14 CCD detectors, each with 2 output channels, and with multiple choices for pixel binning and number of Time Delay and Integration lines. HiRISE will support Mars exploration by locating and characterizing past, present, and future landing sites, unsuccessful landing sites, and past and potentially future rover traverses. We will investigate cratering, volcanism, tectonism, hydrology, sedimentary processes, stratigraphy, aeolian processes, mass wasting, landscape evolution, seasonal processes, climate change, spectrophotometry, glacial and periglacial processes, polar geology, and regolith properties. An Internet Web site (HiWeb) will enable anyone in the world to suggest HiRISE targets on Mars and to easily locate, view, and download HiRISE data products.

/pdf/mars-reconnaissance-orbiter-s-high-resolution-imaging-4bjw0ks5y9.pdf

Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE)

http://www2.ess.ucla.edu/~manning/pdfs/tm07b.pdf

The solubility of fluorite in H2O and H2O–NaCl at high pressure and temperature

The mineral-fluid equilibria that govern silica redistribution by aqueous fluids in subduction zones were evaluated at constant pressure and temperature in the model system MgO-SiO2-H2O (MSH). At <...

Phase-Equilibrium Controls on SiO2Metasomatism by Aqueous Fluid in Subduction Zones: Reaction at Constant Pressure and Temperature

http://www2.ess.ucla.edu/~manning/pdfs/mmy15.pdf

Crystal chemical constraints on inter-mineral Fe isotope fractionation and implications for Fe isotope disequilibrium in San Carlos mantle xenoliths

Polymerization of aqueous silica in H2O-K2O solutions at 25-200°C and 1bar to 20kbar

Magmatic augites reacted with high temperature aqueous solutions to form secondary calcic pyroxenes during the subsolidus cooling of the Skaergaard intrusion. Secondary, hydrothermal clinopyroxenes replace wall rock igneous augites at the margins of veins filled with calcic amphibole. These veins are up to several millimeters wide and tens of meters in length. Hydrothermal clinopyroxenes are a ubiquitous and characteristic phase in the earliest veins throughout the Layered Series of the intrusion, and occur rarely in late veins that, in some places, crosscut the early veins. Associated secondary phases in early veins include amphiboles ranging in composition from actinolite to hornblende, together with biotite, Fe-Ti oxides and calcic plagioclase. Hydrothermal clinopyroxenes in late veins may be associated with actinolite, hornblende, biotite, magnetite and albite. Hydrothermal clinopyroxenes are depleted in Fe, Mg and minor elements, and enriched in Ca and Si relative to igneous augites in the Layered Series gabbros. Secondary vein pyroxenes are similar in composition to calcic pyroxenes from amphibolite facies metamorphic rocks. Clinopyroxene solvus thermometry suggests minimum temperatures of equilibration of between 500° and 750° C. These temperatures, combined with numerical transport models of the intrusion, suggest that vein clinopyroxenes could have formed during 20,000 to 60,000 year time intervals associated with a maximum in the fluid flux through fractures in the Layered Series.

/pdf/hydrothermal-clinopyroxenes-of-the-skaergaard-intrusion-5el0t4l21s.pdf

Craig E. Manning

Papers

The solubility of fluorite in H2O and H2O–NaCl at high pressure and temperature

Phase-Equilibrium Controls on SiO2Metasomatism by Aqueous Fluid in Subduction Zones: Reaction at Constant Pressure and Temperature

Crystal chemical constraints on inter-mineral Fe isotope fractionation and implications for Fe isotope disequilibrium in San Carlos mantle xenoliths

Polymerization of aqueous silica in H2O-K2O solutions at 25-200°C and 1bar to 20kbar

Hydrothermal clinopyroxenes of the Skaergaard intrusion