u-pb ages obtained on zircons from the investigated migmatites place new constraints on the evolution of the crustal rocks in the takab area. shrimp u-pb dating of inherited zircon in the melanosome parts of mafic migmatites from the takab complex gives a discordant age with an upper intercept of 2961±72 ma (mswd=0.5) and a lower intercept of 24.2±5.7 ma (mswd=1.7). in the concordia diagram, th...

One of the fundamental geophysical observations made of the Earth is the stratified nature of the continental crust, in which the lower crust comprises denser, more mafic material and the upper crust comprises less dense, more felsic material. This chemically differentiated layered structure is developed and maintained by partial melting at depth and the ascent of magma to shallower crustal lev...

U-Pb ages obtained on zircons from the investigated migmatites place new constraints on the evolution of the crustal rocks in the Takab area. SHRIMP U-Pb dating of inherited zircon in the melanosome parts of mafic migmatites from the Takab complex gives a discordant age with an upper intercept of 2961±72 Ma (MSWD=0.5) and a lower intercept of 24.2±5.7 Ma (MSWD=1.7). In the concordia diagram, th...

Abstract Potassium-rich adakitic rocks have been used to infer high-pressure (HP) melting of thickened or foundered mafic lower crust in post-collisional settings. However, their origin remains debated because potassic rather than sodic nature. We address this debate by investigating the source Oligocene high-K granites southern Tibet, which are widely attributed overthickened crust. Our new da...

The airborne geophysical data gamma-spectrometric and magnetic from Itatira Project (1977) was carried out, in the central region of the State of the Ceará, Brazil. Their processing produced products useful to indirectly identify regional geologic features. The verification and applicability of this approach was tested in a pilot-area whose limits are within the Umirim and Canindé topographic s...

This virtual special issue represents a collection of papers concerning Crustal Melting selected by the Editor from those published on various aspects of this theme in the JMG since 1982. The papers are grouped into sequences that address topics that have been prominent in the JMG during the last 30 years concerning the origin, evolution and tectonic role of migmatites and migmatitic granulites...

Mafic eclogites are found in many orogens as lenses embedded quartzofeldspathic migmatites. These high-pressure relics interpreted either remnants of ancient sutures and thus formed during oceanic subduction or fragments lower crust exhumed from the root orogenic thickened crust. It is critical to distinguish between these two endmember scenarios resulting palaeogeographic geodynamic reconstruc...

Field, structural, and metamorphic petrology investigations of Mabja gneiss dome, southern Tibet, suggest that contractional, extensional, and diapiric processes contributed to the structural evolution and formation of the domal geometry. The dome is cored by migmatites overlain by sillimanite-zone metasedimentary rocks and orthogneiss; metamorphic grade diminishes upsection and is defined by a...

Extreme uplift associated with the formation of the 2.02 Ga Vredefort dome has exposed a substantial cross section through the crystalline early Archean basement complex rocks of the Kaapvaal craton. The rocks comprise polydeformed high-grade tonalite–trondhjemite–granodiorite (TTG) gneisses, migmatites and late-tectonic intrusive granitoids that straddle the upper amphibolite-to granulite–faci...