At the southernmost part of Tierra del Fuego a few outcrops and erratic boulders of alkali basaltic rocks with ultramafic enclaves have been studied. Alkali basalt plugs or pipes hitherto identified are scarce, and host rocks are constituted by slates that belong to Mesozoic deposition. The petrography, texture and composition of the basalt and xenoliths were investigated by petrographic micros...

Kinetic and fluid dynamic constraints on deepseated magma migration rates suggest ascent velocities in the range 10 to 30 m/s, 10 -1 to 10m/s and 10 -2 to 5m/s for kimberlitic, garnet peridotite-bearing and spinel peridotite-bearing alkalic magmas. These rates virtually demand translithospheric magma transport by a fracture as opposed to diapiric mechanism. The hypothesis that volatile exsoluti...

Abstract We present a new experimental dataset for reaction experiments between natural amphibole-clinopyroxene metasomes (hornblendite) and synthetic lherzolite that produced Na-rich alkaline melts. Experiments were conducted at 1, 3 4 GPa 1000–1300 °C. The generated melts range from foidite over basanite to phonotephrite. At 1 1000 1100 °C amphibole decompression-breakdown products generate p...

A detailed petrographic and mineralogical investigation of olivine-phlogopite micro-ijolite xenoliths from Oldoinyo Lengai, Tanzania indicates a complex evolutional history. These consist diverse textural subdomains characterized by minerals ranging early-formed olivine, through diopside-hosted perovskite phlogopite, to evolved aegirine-augite titanite. Thermometry mineral compositions in the s...

Abstract Maar‐diatreme volcanoes are small volcanic structures with a funnel‐shaped crater surrounded by tephra‐ring. They usually formed the explosive phreatomagmatic eruptions when groundwater comes into contact magma. We focus on such structure in geodynamically active western Eger Rift (Czech Republic) and present results from multidisciplinary geophysical investigation calibrated drilling ...

Abstract The accessories perovskite, pyrochlore, zirconolite, calzirtite and melanite from carbonatites carbonate-rich foidites the Kaiserstuhl are variously suited for in situ determination of their U–Pb ages Sr, Nd- Hf-isotope ratios by LA-ICP-MS. 143 Nd/ 144 Nd may be determined precisely all five phases, 176 Hf/ 177 Hf only 87 Sr/ 86 Sr perovskites pyrochlores. belong to one three magmatic ...

Decompression melting of the upper mantle produces magmas and volcanism at Earth's surface. Experimental petrology demonstrates that presence CO2 H2O enhances peridotite anywhere within down to approximately 200–300 km depth. The melts with compositions ranging from carbonate-rich silicate-rich unavoidably affects geophysical signals retrieved mantle. Geochemical investigations erupted intrapla...

THE mineral tacharanite has been recently re-examined by Cliff et al. (1975). They worked on material from the original locality, Portree, in Scotland (Sweet, I961) and from a few new European localities described between I97I and I974. None of the post-Sweet authors, however, refer to the second discovery of the mineral from Tasmania where it was identified by this writer in I961 and recorded ...