Precise Fe/Mn ratios and MnO contents have been determined for basalts from the Hawaiian shields of Ko’olau and Kilauea by inductively coupled plasma mass spectrometry. It is well known that the youngest Ko’olau (Makapu’u-stage) shield lavas define a geochemical endmember for Hawaiian lavas in terms of CaO and SiO2 contents and isotopic ratios of O, Sr, Nd, Hf, Pb, and Os. We find that their Mn...

12 Observations in the USA, Iceland, and Tenerife, Canary Islands, reveal how processes occurring 13 during basaltic eruptions can result in complex physical and stratigraphic relationships between lava 14 and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can 15 disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity ar...

introduction mesgar iron occurrence is located in northwestern part of the central iran, 115 km south of zanjan. although there is a sequence of volcanic-pyroclastic rocks accompanied by iron mineralization, no detailed works had been conducted in the area. the present paper provides an overview of the geological framework, the mineralization characteristics, and the results of geochemical stud...

Radon-222 diffusion in an anhydrous andesitic melt was investigated. The melts were glass discs formed artificially from melted volcanic materials. Solutions of the relevant diffusion equations were done by the explicit finite difference method. Results were compared to analytical solutions reported in the literature and good agreement was found. We have shown that the explicit finite differenc...

Hornblende occurs in some andesitic and basaltic rocks of calc-alkaline affini1y, where it is commonly associated with olivine. The texture, eruption history, and composition are interpreted to indicate that hornblende commonly forms as a product of reaction between olivine and basaltic and andesitic liquids. The natural hornblendes probably formed within the crust at temperatures between 960o ...

The failure mode of lava-dilatant or compactant-depends on the physical attributes of the lava, primarily the porosity and pore size, and the conditions under which it deforms. The failure mode for edifice host rock has attendant implications for the structural stability of the edifice and the efficiency of the sidewall outgassing of the volcanic conduit. In this contribution, we present a syst...

The role of a mafic component in the petrogenesis of Oceanic Island Basalts (OIBs) is highly debated. As the best studied OIB, Hawaiian lavas provide critical insights into OIB genesis. At a given MgO content, the CaO content in the melt has been used to distinguish between partial melts of peridotite and garnet pyroxenite/eclogite. However, calculations using the BATCH program show that CaO co...

Samples of basalt were collected during the Rapid Response cruise to Loihi seamount from a breccia that was probably created by the July to August 1996 Loihi earthquake swarm, the largest swarm ever recorded from a Hawaiian volcano. Po–Pb dating of two fresh lava blocks from this breccia indicates that they were erupted during the first half of 1996, making this the first documented historical ...

The Christmas copper mine is in the Banner mining district, Gila County, Arizona. It is 8 miles north of Winkelman and 22 miles south of Globe. The mine was opened in 1905; to the end of 1943 it had produced about 55,340,000 pounds of copper. In 1946 it was operated under lease. The ore is high-lime fluxing ore, required by the smelter at Hayden. The ore produced during 1942 averaged 2.16 perce...

[1] We measured He, Sr, Nd, Pb, and Os isotope ratios and major and trace element concentrations in stratigraphically and paleomagnetically controlled shield-stage lavas from Kauai, Hawaii. The range of He/He ratios (17–28 RA) from Kauai is similar to that reported from Loihi and thus challenges the prevailing notion that high He/He ratios are restricted to the preshield stage of Hawaiian magma...