Chemical stratigraphy, Iceland Research Drilling Project, Reydarfjordur, eastern Iceland

Abstract

Major element data are reported for lavas and dikes from a 3.2‐km section through the eastern Iceland lava pile. The section includes a 1.2‐km subaerial exposure and a 1.9‐km sequence drilled by the Iceland Research Drilling Project (IRDP). Alteration increases down‐section, although primary magma chemistry may be interpreted from FeO* Al2O3, TiO2, P2O5 and (to a lesser extent) SiO2 in addition to immobile trace elements. Lava compositions range from MgO‐rich tholeiite to SiO2‐rich icelandite, while dikes range from tholeiite to tholeiitic andesite. Three stratigraphic divisions based on volcanologic and trace element criteria (e.g., Ce/Yb and Zr/Y) are confirmed by major elements. Upper and lower groups are predominantly basaltic while the middle group includes a high proportion of silicic lavas. Variation within groups conforms to simple models combining fractional crystallization and accumulation of phenocryst plagioclase. During build‐up of the pile, eruptive phases commenced with silica‐rich magma and frequently terminated with basaltic or intermediate plagioclase cumulates. Dike chemistry resembles that of upper group lavas and also the nearby Breiddalur volcano. Middle group lavas probably derive from a buried silicic complex, while the lower group may represent the flank of a more deeply buried complex. Chemical stratigrapy is consistent with iterative burial with spreading of lenticular basaltic‐silicic complexes. Magma supply, fractionation, and mixing are considered in the framework of such kinematic models, although it is premature to draw direct analogies to the active Neogene zone of Iceland.

Magnetic and petrologic characterization of synthetic Martian basalts and implications for the surface magnetization of Mars

“…The second composition is identical to the first in all respects save Fe (in which the second composition is poorer), Al (richer), and Ca (slightly richer). The relative abundances of Fe and Al in the second composition (Fe/Al = 0.4) typify those of terrestrial basalt [e.g., Leeman et al , 1990; Flower et al , 1982] and satisfy compositional constraints posed by deconvolved thermal emission spectrometer (TES) data from the Mars surface [e.g., Hamilton et al , 2001]. Some experimentalists have also proposed that moderate‐Fe/Al basalts are parental to Mars meteorite materials [ Nekvasil et al , 2007].…”

Hawaiian basalt and Icelandic rhyolite: Indicators of differentiation and partial melting

“…A compilation of the chemical data collected from the deep drill hole at Reydarfjordur (FLOWER et al, 1982) is shown by Figure 12. The only Mgrich lavas shown here are the few picrites of the Reykjanes Peninsula, which are the most notable such rocks in Iceland (e.g., JAKOBSSON et al, 1978).…”

Deep crustal reflectors under Reydarfjördur, eastern Iceland:crustal accretion above the Iceland mantle plume

“…The di¡erence in P-wave seismic velocity between the olivine basalts and the basaltic andesites/Icelandites is approximately 0.5 km s {1 . The plagioclase cumulates identi¢ed by Flower et al (1982) have a fairly ma¢c composition and a similar estimated velocity to the low-Mg basalts (Fig. 9).…”

“…Furthermore, the di¡erences in lava composition between the groups a¡ects the average seismic velocity of each group. To estimate the e¡ect of compositional variation between lava groups we have taken the major element composition of 292 lavas within the ReydarfjÎrdur lava pile (from Flower et al 1982), estimated the norm mineralogy for ¢ve petrological groups (after Robinson et al 1982) using the CIPW scheme (Cross et al 1903) and proceeded to estimate seismic velocities for these rocks using the Voigt^Reuss^Hill averaging scheme (Hill 1952) with mineral properties from Carmichael (1990) and Qiu, Priestley & McKenzie (1996) (Fig. 9).…”