New thermal‐petrologic models of subduction zones are used to test the hypothesis that intermediate‐depth intraslab earthquakes linked metamorphic dehydration reactions in subducting oceanic crust and mantle. We show there is a correlation between patterns seismicity locations predicted hydrous minerals: Earthquakes occur slabs where expected, they absent from parts be anhydrous. propose plate can consist four petrologically seismically distinct layers: (1) hydrated, fine‐grained basaltic...

[1] A recent global compilation of the thermal structure subduction zones is used to predict metamorphic facies and H2O content downgoing slabs. Our calculations indicate that mineralogically bound water can pass efficiently through old fast (e.g., in western Pacific), whereas hot such as Cascadia see nearly complete dehydration subducting slab. The top slab sufficiently all upper crust, including sediments volcanic rocks, predicted dehydrate significantly. degree depth deeper crust...

We present a new compilation of physical properties minerals relevant to subduction zones and phase diagrams for mid‐ocean ridge basalt, lherzolite, depleted harzburgite, serpentinite. use these data calculate H 2 O content, density seismic wave speeds zone rocks. These calculations provide basis evaluating the factory, including (1) presence hydrous phases distribution within zone; (2) densification subducting slab resultant effects on measured gravity shape; (3) variations in resulting...

The largest tract of ultrahigh‐pressure rocks, the Dabie‐Hong'an area China, was exhumed from 125 km depth by a combination normal‐sense shear beneath hanging wall Sino‐Korean craton, southeastward thrusting onto footwall Yangtze and orogen‐parallel eastward extrusion. Prior to exhumation UHP slab extended into mantle downdip distance 125–200 at its eastern end, whereas it subducted perhaps only 20–30 far western end ∼200 away. Structural reconstructions imply that >10 thick. U/Pb zircon...

The amount of H 2 O subducted to postarc depths dictates such disparate factors as the generation arc and back‐arc magmas, rheology mantle wedge slab, global circulation O. Perple_X was used calculate phase diagrams rock physical properties for pressures 0.5–4.0 GPa temperatures 300–900°C a range bulk compositions appropriate subduction zones. These data were merged with zone fluxes generate model flux depths. For metasomatized igneous rocks, scales K in hot slabs. Metasomatized ultramafic...

The composition of much Earth's lower continental crust is enigmatic. Wavespeeds require that 10–20% the third mafic, but available heat-flow and wavespeed constraints can be satisfied if elsewhere contains anywhere from 49 to 62 wt% SiO 2 . Thus, contrary common belief, in many regions could relatively felsic, with contents similar andesites dacites. Most less dense than underlying mantle, mafic lowermost unstable likely delaminates beneath rifts arcs. During sediment subduction, subduction...

The onset and evolution of the Dead Sea transform are re-evaluated based on new in situ U-Pb dating strain analyses mechanically twinned calcites. Direct 30 syn-faulting calcites from 10 different inactive fault strands indicates that oceanic-to-continental plate boundary initiated between 20.8 18.5 Ma within an ∼10-km-wide distributed deformation zone southern Israel. Ages northern (17.1–12.7 Ma) suggest northward propagation establishment a well-developed >500-km-long plate-bounding 3 m.y....

The orogenic architecture of the world's largest ultrahigh‐pressure exposure, Hong'an‐Dabie Mountains Triassic Qinling‐Dabie belt, is dominated by Cretaceous and Cenozoic structures that contributed to its exhumation from ≤30 km depth. magmatic crustal recycling (≥50% for entire Dabie) heating (>250° >700°C) were most prominent in Dabie, exhumation, magmatism, cooling all controlled transtension. Exhumation was accomplished principally an asymmetric Cordilleran‐type extensional complex...

In understanding of ophiolite emplacement requires knowledge the elapsed time between igneous crystallization and intraoceanic thrusting, rate duration that thrusting. Hornblende 40 Ar/ 39 Ar ages demonstrate oceanic crust in Oman crystallized cooled to ∼825 K 1–2 m.y. from metamorphic rocks cross‐cutting dikes require basal thrust fault beneath also below Motion along sole accounted for 200 km displacement at a 100–200 mm/yr. On basis age relationships thermal considerations, we favor...

Anhydrous metasedimentary and mafic xenoliths entrained in 3-million-year-old shoshonitic lavas of the central Tibetan Plateau record a thermal gradient reaching about 800 degrees to 1000 C at depth 30 50 kilometers; just before extraction, these same were heated as much 200 C. Although rocks show that crust is hot enough cause even dehydration melting mica, absence hydrous minerals, match our calculated P-wave speeds Poisson's ratios with seismological observations, argue against presence...

Research Article| August 01, 1999 Structure and petrology of Tauride ophiolites mafic dike intrusions (Turkey): Implications for the Neotethyan ocean Yildirim Dilek; Dilek 1Department Geology, Miami University, Oxford, Ohio 45056 Search other works by this author on: GSW Google Scholar Peter Thy; Thy 2Department University California, Davis, California 95616 Bradley Hacker; Hacker 3Department Geological Sciences, Santa Barbara, 93106 Sidsel Grundvig 4Geologisk Institut, Aarhus Universitet,...

Research Article| December 01, 2001 Sedimentary record and tectonic implications of Mesozoic rifting in southeast Mongolia S.A. Graham; Graham 1School Earth Sciences, Stanford University, Stanford, California 94305, USA Search for other works by this author on: GSW Google Scholar M.S. Hendrix; Hendrix 2Department Geology, University Montana, Missoula, Montana 59812, C.L. Johnson; Johnson 3School D. Badamgarav; Badamgarav 4Center Paleontology, Mongolian Academy Peace Avenue 63, Ulaanbaatar,...

Structural, thermobarometric, and thermochronologic investigations of the Kangmar Dome, southern Tibet, suggest that both extensional contractional deformational histories are preserved within dome. The dome is cored by an orthogneiss which mantled staurolite + kyanite zone metasedimentary rocks; metamorphic grade dies out up section defined a series concentric kyanite‐in, staurolite‐in, garnet‐in, chloritoid‐in isograds. Three major events, two older penetrative events younger doming event,...

An Excel macro to calculate mineral and rock physical properties at elevated pressure temperature is presented. The workbook includes an expandable database of parameters for 52 rock‐forming minerals stable high pressures temperatures. For these the elastic moduli, densities, seismic velocities, H 2 O contents are calculated any specified P T conditions, using basic thermodynamic relationships third‐order finite strain theory. modes suites rocks also specifiable, so that their predicted...

New U/Pb zircon and Th/Pb monazite ages are presented from the giant Sulu ultrahigh‐pressure (UHP) terrane. Combined with Sm/Nd ages, Rb/Sr inclusion relationships, geologic they help define timing of peak recrystallization, subsequent amphibolite‐facies metamorphism, architecture Dabie‐Sulu suture zone between collided Sino‐Korean Yangtze cratons. The data indicate a ∼15 Myr record UHP first clearly documented for terrane; this requires that continental subduction in orogen involved...