Dunite nodules (Foss) and megacrysts of olivine (Fos3 s4 ) and clinopyroxene (FS13W043En44) are present as rare inclusions in the rhyodacite (~ 66wt %SiO z ) of Kauaopuu Ridge, Oahu, Hawaii. The rhyodacite is interbedded with caldera-filling tholeiitic lavas of the Waianae volcano. Results: (I) Dunite nodules (::;; I cm) consist of xenomorphic-granular olivine and minor chrome spinel and clinop...

Tutuila is a basaltic volcanic island within the east southeasterly trending Samoa Island chain in the Pacific Ocean. Potassium-argon ages on 38 whole rock samples oflavas and intrusives demonstrate that the main period of subaerial volcanism occurred over a relatively short interval of about 0.6 Ma in the Early Pleistocene. The major shield volcano, Pago, was built between about 1.54 and 1.28 ...

The Pretoria Saltpan crater is a well-preserved 220,000 year-old, 1.13 km-diameter, simple impact crater. The crater was formed in Nebo granites of the Bushveld Complex. Some minor intrusions thought to be younger than the Nebo granite are present at the crater and have earlier been believed to support a volcanic origin of the structure, but recent geological studies showed them to be part of t...

introduction agates are presumed as a kind of precious stone that could be formed in magmatic, metamorphic and even sedimentary environment. mechanism for agate formation is not clear and is produced in laboratories. some hot springs and geothermal activity or white chimneys in the ocean floor, have some deposits like chalcedony but never produce agate. agate formation temperature varies betwee...

Introduction Damavand volcano is a large composite cone (≥ 400 km3) with height elevation (5678m) above sea level, in Central Alborz. This volcano consists of two buildings including old lavas between 1.8 to 0.8 Ma in the northern and eastern part of the current cone and young lavas with about 0.4 to 7 ka years in the south and west part. Trachytic and trachy-andesitic lavas are the most abund...