Clinopyroxene phenocrysts and microphenocrysts in potassic and sodic Eosen alkaline volcanic rocks from the northern Lahrud (NW Iran) record various stages in the crystallization and evolution history of the alkaline melt as well as its origin. The rock series hosting the clinopyroxene phenocrysts is phonolitic tephrite and tephritic phonolite composition. Theses rocks generally show porphyriti...

Meter-scale DSL-120 sonar mapping and coregistered Argo II photographic observations reveal changes in eruptive style that closely follow the third-order structural segmentation of the ridge axis on the southern East Pacific Rise, 17°11’-18°37’S. Near segment ends we observe abundant basaltic lava domes which average 20 m in height and 200 m in basal diameter and have pillow lava as the dominan...

Serpentinized oceanic lithosphere may be an important source for boron and other fluid-mobile elements that are anomalously enriched in arc volcanic rocks. However, the integrated water/rock ratios associated with different styles of serpentinization may be variable. For example, large water/rock ratios are involved in the serpentinization of abyssal peridotites exhumed to the seafloor, whereas...

Gazestan magnetite-apatite deposit is located in Central Iran and Bafq region, which has been occurred in form of veins, veinlets, and small apatite lenses as well as magnetite in metasomatic rock types such as green chlorite-actinolite rock units. These rocks are situated in the carbonate-volcanic complex of Upper Precambrian-Lower Cambrian Rizo formation. In this study, staged factor analysis...

Mount Rainier is one of the most seismically active volcanoes in the Cascade Range, with an average of one to two high-frequency volcano-tectonic (or VT) earthquakes occurring directly beneath the summit in a given month. Despite this level of seismicity, little is known about its cause. The VT earthquakes occur at a steady rate in several clusters below the inferred base of the Quaternary volc...

Geochemical research into volcanic rocks often involves isotopic analysis of whole rock powders. The method of Deniel and Pin (Anal. Chim. Acta, 2001, 426, 95-103) for simultaneous isolation of strontium and lead using extraction chromatography via Sr spec resin was therefore adapted into a straightforward procedure for Sr and Pb isotope ratio determination by multi-collector inductively couple...

[1] The cryptoendolithic habitat of the Antarctic Dry Valleys has been considered a good analogy for past Martian ecosystems, if life arose on the planet. Yet cryptoendoliths are thought to favor the colonization of rocks that have a preexisting porous structure, e.g., sandstones. This may weaken their significance as exact analogues of potential rockcolonizing organisms on Mars, given our curr...

in the centeral iranian volcanic belt (civb), north-west of shahre-babak, in area of javazm, dehaj and khabr, about 20 plutonic porphyritic tonalitic to granodioritic masses (1-50 km2) are intruded into a varity of rock sequences from eocene to early miocene in age. tonalitic and granodioritic rocks are some part of dehaj-sardoieh belt and having early miocene age. the civb contains intrusive a...