Numerous important Miocene and early Pliocene epithermal Au-Ag deposits are present in the northern Great Basin. Most deposits are spatially and temporally related to two magmatic assemblages: bimodal basaltrhyolite and western andesite. These magmatic assemblages are petrogenetic suites that reflect variations in tectonic environment of magma generation. The bimodal assemblage is a K-rich thol...

Planetary materials contain an abundance of 3d transition metals. They occur in mineral phases that formed in a wide range of environments, e.g., the gaseous envelopes surrounding ancient stars and the early solar nebula. The ability of such metals to occur in multiple oxidation states makes them potentially useful recorders of the redox conditions under which their host assemblage formed or la...

Seven manganese minerals have been observed in geodes from Chihuahua, Mexico. Ramsdellite occurs in a number of different habits, but the morphology and precession X-ray patterns suggest that it is pseudomorphous after groutite. Pyrolusite is found only in association with ramsdellite and is believed to be an alteration product of that mineral. Todorokite generally occurs as a late-stage fibrou...

Matlab scripts that apply the Bence & Albee (1968) matrix correction algorithm to X-ray intensity data collected as element maps on a Cameca SX-50 microprobe are used to produce two-dimensional maps of oxide weight percent and cation proportions for SiO2, Al2O3, FeO, MnO, MgO, CaO, Na2O and K2O. Once generated, large data sets of mapped oxide weight percent values or cation numbers that retain ...

Lawsonite eclogites represent fossil records of processes occurring during subduction of cold and fast-subducting slabs, and provide the opportunity to investigate the thermal and metamorphic evolution of palaeosubduction zones. Occurrences of lawsonite eclogites are rare because lawsonite is often replaced during exhumation. We report here, for the first time, the occurrence of a lawsonite ecl...

late neoproterozoic-early cambrian schists have been occurred in southwest of zanjan city from the soltanieh belt. the soltanieh belt in northwest of iran is uplifted basement of precambrian-paleozoic in main central iran zone and includes outcrops of precambrian, paleozoic and mesozoic formations. late neoproterozoic-early cambrian schists, the oldest stratigraphy unit in the region, consist o...

The Miocene pyroxene andesite lava flows are exposed in southeastern edge of Urumieh Dokhtar Magmatic assemblage in Iran. The hypocrystalline andesite in parts contain conspicuous co-magmatic igneous enclaves which are dark grey and occur mostly as spherical and occasionally as ribbon shapes with some showing chilled margins. Petrographic study shows that the ribbon type enclaves have been form...

Buchitic glassy rocks appear within the skarn of contact metamorphic aureole of Feshark intrusive complex situated 30 km northeast of Isfahan. Intrusive complex is a multistage intrusion . Noritic gabbro is the first inttrusion which is invaded later on by a granitic melt. Granitic melt has metasomatically altered the gabbro and as a consequence a suite of hybrid rocks like monzogabbro, m...

Toxic metalliferous mine-tailings pose a significant health risk to ecosystems and neighboring communities from wind and water dispersion of particulates containing high concentrations of toxic metal(loid)s (e.g., Pb, As, Zn). Tailings are particularly vulnerable to erosion before vegetative cover can be reestablished, i.e., decades or longer in semi-arid environments without intervention. Meta...