Basalt alkali

Thomas JB, Bodnar RJ, Shimizu N, Sinha AK (2002) Determination of zircon/melt trace element partition coefficients from SIMS analysis of melt inclusions in zircon. Geochim Cosmochim Acta 66 2887-2901 Thompson GM, Malpas J (2000) Mineral/melt partition coefficients of oceanic alkali basalts determined on natural samples using laser ablation-inductively eouple plasma-mass spectrometry (LAM-ICP-MS). Mineral Mag 64 85-94... 

On a still shorter timescale, Sigmarsson (1996) used Pb- Ra disequilibria in Surtsey and Heimaey (Iceland) lavas to infer the differentiation time from the Surtsey alkali basalt erupted in 1963-1967 to the Heimaey hawaiites and mugearites (1973 eruption). The ( Pb/ Ra) ratios increase from the basalts to the evolved lavas, which can be explained by a closed system differentiation of about 10 years, a value similar to the time elapsed between the two eruptions. Thus, the Heimaey eruption is interpreted as a consequence of the injection in the crust of a small volume of basaltic magma, 10 years before eruption, a duration long enough to allow its differentiation towards hawaiite and mugearite compositions. 

Other variations in ratios observed in the alkali basalts of the 1718 AD... 

Hemond C, Hofmann AW, Heusser G, Condomines M, Rhodes JM, Garcia MO (1994) U-Th-Ra systematics in Kilauea and Manna Loa basalts. Contrib Mineral Petrol 116 163-180 Hirose K (1997) Partial melt compositions of carbonated peridohte at 3 GPa and role of CO2 in alkali basalt magma generation. Geophys Res Lett 24 2837-2840... 

The amli pluton is subalkaline and calc-alkaline, and mainly diorite porphyry, granodiorite, quartz monzonite, and granite-porphyry in composition (Fig. 3). The metadiabase is alkali basalt in composition,... 

Both of the soils are enriched in various elements, like zirconium, titanium, beryllium, niobium, and strontium, due to their enlarged content in the alkali basalts and phonolites of the East-African Rift. We can see that soils of Tanzanian Dry Savanna ecosystems contain niobium 11 times, beryllium and molybdenum 6 times, and titanium and zirconium 4 times as high as compared to the respective crust concentrations (darks) of these metals. In the Ugandan soils, the chromium content is 7 times higher... 

Caroff, M., Maury, R. C., Leterrier, J., Joron, J.-L., Cotten, J. Guille, G. (1993). Trace element behavior in the alkali basalt-comenditic trachyte series from Mururoa Atoll, French Polynesia. Lithos, 30, 1-22. 

Sulfur occurs in a variety of forms in the mantle, the major sulfur phase is monosulfide solid solution between Fe, Ni, and Cu. Recent ion microprobe measurements on sulfide inclusions from megacrysts and pyroxenite xenohths from alkali basalts and kimberlites and in diamonds gave 5 " S-values from — 11 to - - 14%c (Chaussidon et al. 1987, 1989 Eldridge et al. 1991). Sulfur isotope variations within diamonds exhibit the same characteristics as previously described for carbon i.e., eclogitic diamonds are much more variable than peridotitic diamonds. 

Cebria, J.M. and Lopez-Ruiz, J., 1995. Alkali basalts and leucitites in an extensional intracontinental plate setting The late Cenozoic Calatrava Volcanic Province (central Spain). Lithos, 35 27-46. 

Alkali basalts are here defined as nepheline- and olivine-normative basaltic rocks with moderate enrichment in alkalis, which fall in the basalt field on the TAS diagram above the divide between alkaline and subalkaline fields of Irvine and Baragar (1971). 

Petrological and geochemical data are available for a few dredged samples from some seamounts. Rock compositions range from tholeiitic basalt to alkali basalt, hawaiite and basanite (Calanchi et al. 1989 and references therein Fig. 8.16). Tholeiites have been found at Tetide volcano. These rocks are sparsely porphyritic, with phenociysts of orthopyroxene rimmed... 

Mafic rocks from the Sicily Province display variable abundances of incompatible elements, which increase from tholeiites to alkali basalts and nephelinites. However, all the rocks show low LILE/HFSE ratios, typical of intraplate basalts, in contrast with the high LILE/HFSE compositions of volcanism from the Aeolian arc and the Italian peninsula. They have a relatively restricted range of Sr-Nd isotopic compositions, but variable Pb isotopic ratios, which fall along a trend connecting HIMU and intermediate compositions between DMM and EMI mantle. 

Rock type Tholeiitic basalt Alkali-basalt Hawaiite Basanite... 

Rock type Andesite Rhyolite Trachy- andesite Basanite Hawaiite Hawaiite Tephri- phono- lite Alkali basalt Ande- site... 

Longhi J. and Pan V. (1988) A reconnaissance study of phase boundaries in low-alkali basaltic liquids. J. Petrol. 29, 115-147. 

Copper. The abundance of copper in the depleted mantle raises a particular problem. Unlike other moderately compatible elements, there is a difference in the copper abundances of massive peridotites compared to many, but not all, of the xenolith suites from alkali basalts. The copper versus MgO correlations in massive peridotites consistently extrapolate to values of 30 ppm at 36% MgO, whereas those for the xenoliths usually extrapolate to <20 ppm, albeit with much scatter. A value of 30 ppm is a relatively high value when chondrite normalized ((Cu/Mg)N = 0.11), and would imply Cu/Ni and Cu/Co ratios greater than chondritic, difficult to explain, if true. However, the copper abundances in massive peridotites are correlated with sulfur, and may have been affected by the sulfur mobility postulated by Lorand (1991). Copper in xenoliths is not correlated with sulfur, and its abundance in the xenoliths and also inferred from correlations in basalts and komatiites points to a substantially lower abundance of 20 ppm (O Neill, 1991). We have adopted this latter value. 

Roden M. K., Hart S. T., Frey F. A., and Melson W. G., Sr (1984) Nd and Pb isotopic and REE geochemistry of St. Paul s Rocks the metamorphic and metasomatic development of an alkali basalt mantle source. Contrib. Mineral. Petrol. 85, 376-390. 

Table 1 Major groups of mantle xenoUths in kimberUte-related and alkali basalt series volcanic rocks (after Harte and Hawkeswortb, 1989). Textural classification follows that of Harte (1977). Terminology for phlogopite-rich mafic mantle xenoUths from Gregoire et al. (2002). For supplementary data and classifications see Nixon (1987), table 62. 

---