The Earth's sole active carbonatite volcano, Oldoinyo Lengai (Tanzania), is presently erupting unique natrocarbonatite lavas that are characterized by Na- and K-bearing magmatic carbonates of nyerereite [Na2Ca(CO3)2] and gregoryite [(Na2,K2,Ca)CO3]. Contrarily, the vast majority of older, plutonic carbonatite occurrences worldwide are dominated by Ca-(calcite) or Mg-(dolomite)-rich magmatic car...

If relationships exist between the frequency of geomagnetic reversals and the morphology, secular variation, and intensity of Earth's magnetic field, they should be best expressed during superchrons, intervals tens of millions of years long lacking reversals. Here we report paleomagnetic and paleointensity data from lavas of the Cretaceous Normal Polarity Superchron that formed at high latitude...

The most important examples of magmatic ore deposits in volcanic rocks are Fe-Ni-Cu-(PGE) sulphides associated with Archean and Proterozoic komatiitic lava channels (Lesher, 1989). Komatiitehosted ores contain ~25% of the world’s nickel sulphide resource (≥ 0.8% Ni), including significant amounts of copper and platinum group elements (Ross and Travis, 1981). Field, experimental, and theoretical...

Abstract Magma mixing is a widespread magmagenic process. However, its significance in the formation of ultrapotassic magmas has been largely overlooked so far as they are commonly thought to originate directly from mantle and ascend rapidly through crust. The Hezhong lavas Western Yunnan (SW China) (basaltic) trachy-andesitic composition. These rocks display porphyritic textures with olivine, ...

In subduction zones, sediments and hydrothermally altered oceanic crust, which together form part of the subducting slab, contribute to the chemical composition of lavas erupted at the surface to form volcanic arcs. Transport of this material from the slab to the overlying mantle wedge is thought to involve discreet melts and fluids that are released from various portions of the slab. We use a ...

Pahoehoe lava flows are common in every basaltic province, and their submarine variants, pillow lavas and sheet flows, cover the bulk of the Earth. Pahoehoe flows are emplaced by inflation—the injection of molten lava underneath a solidified crust. Only in the past few years has an understanding of the inflation process and the ability to recognize ancient inflated lava flows been achieved. All...

Introduction: Elephant Moraine (EET) 87521 is a polymict mare basalt breccia containing very-low-titanium (VLT) basalt components and rarer KREEP components. [1] showed that within pyroxene from VLT lithic clasts of EET87521, there were two distinct trends in a plot of Ti/(Ti+Cr) versus Fe/(Fe+Mg) (Figure 1). They suggested that the two fractionation trends (A and B) were the result of differen...