The assumptions of conventional whole-rock and mineral isochron radioisotope dating were tested using a suite of radioisotopes from two Precambrian rocks. Amphibolite from the Beartooth Mountains of Wyoming shows evidence of thorough metamorphism by isochemical processes from andesite by an early Precambrian magma-intrusion event. A diabase sill, exposed within the wall of Grand Canyon at Bass ...

dehsalm metamorphic complex located in east of iran consists of regionally metamorphosed rocks intruded by three phases of granitic masses. synkinematic porphyroblasts of garnet from staurolite-garnet schist present well preserved growth zoning. electron microprobe analysis of selected garnets was carried out to interpret the origin and pattern of zoning in amphibolite facies garnets and its im...

New mapping, geochronology, and geochemistry of the supracrustal enclave and associated orthogneisses at Akilia, West Greenland, support a >3825 6 Ma age for the sequence and a chemical sedimentary origin for the controversial Fe-rich quartz-pyroxene gneisses. Lithologies of the enclave comprise laterally continuous, mappable units of mafic amphibolite, ultramafic rocks, and two Fe-rich quartzp...

Oxygen isotope ratios and rare earth element (REE) concentrations provide independent tests of competing models of injection v. anatexis for the origin of migmatites from amphibolite and granulite facies metasedimentary rocks of the Adirondack Mountains, New York. Values of dO and REE profiles were measured by ion microprobe in garnet–zircon pairs from 10 sample localities. Prior U–Pb SIMS dati...

It is well established that the major and minor element contents of chromites are subject to change during greenschist amphibolite facies metamorphism. During upper metamorphism, chromite can be completely converted chrome magnetite. However, not all elements affected same degree, concentrations +2 ions (e.g. Zn, Co, Mn) being particularly vulnerable modification. The degree which trace element...

-Ti, V, Cr, Fe, Co, Ni, Cu, and Zn have been analyzed from Sites 211,213,214,215,and 216 of DSDP Leg 22 of the Clomar Challenger in the northeastern lndian Ocean. According to these trace elements, three different types of source material are broadly defined: the basin floor basalts with a composition sirnilar to tholeiites from mid-oceanic ridges, the basalts and the differentiated rocks from ...

Paleozoic gneissic granitoids are an important lithologic component of the Shoo Fly Complex of the central Sierra Nevada, California. Field relations, petrographic, and geochemical studies indicate that the gneisses were originally intruded as a seri.es of plutons ranging from gabbro (oldest) to granite and granodiorite (median age) to syenite (youngest) with the granitoid types predominating. ...

In this study, twenty five partially vitrified rocks and four samples of collected on the top hill called Serravuda (Acri, Calabria, Italy) are analyzed. The goal is to shed light origin these enigmatic materials. analyzed a breccia cemented rock fragments (gneiss, granitoid, amphibolite fragments) which extends for more than 10 m, forming continuous mass along northern north-west border flat h...