Morphology, Geochemistry, and Evolution of Serocki Volcano

Abstract

Basalts collected during drilling and diving programs on Serocki Volcano mostly fall within a limited compositional range, and are moderately evolved, normal MORBs with distinctive high MgO contents (averaging 7.60 wt%) and high A1 2 0 3 concentrations (averaging 16.14 wt% in whole rock samples). However, samples recovered from within the central crater have lower Ti0 2 and FeO*/MgO, and higher MgO and A1 2 0 3 concentra tions, and are most similar to glasses recovered at Site 649 about 45 km to the north. Comparison of the observed geochemical variations with low-pressure experimental work and other samples from the region suggests that the Serocki Volcano and Site 649 data are compatible with crystal-liquid fractionation involving both olivine and early-stage clinopyroxene, as well as plagioclase, and that the sources may be similar even though Sites 648 and 649 are located in different, but adjacent, spreading cells.Consideration of the stratigraphy and morphology of Serocki Volcano suggests that this feature is more properly described as a megatumulus or lava delta, associated with a steeper, conical peak to the southwest. The evolution of Serocki Volcano involved early construction of a marginal rampart of pillows, followed by doming of this feature and the formation of a perched lava pond. Draining of this pond resulted in collapse and the formation of the central crater.

Site 920

“…= 0.003). This is similar to the range of bulk-rock compositions from Site 670 (Di Donnato et al, 1990;Humphris et al, 1990) and Alvin (Casey, unpubl. data) samples from the MARK region, also plotted in Figure 29.…”

The role of seamount volcanism in crustal construction at the Mid‐Atlantic Ridge (24°–30°N)

“…High resolution side scan sonar images of regions south of the Kane transform [Kong et al, 1988], and north of the transform (R. C. Searle, personal communication, 1991) indicate that most features of this type are volcanic constructions. (An alternative identification of one of these features, Serocki Volcano, as a megatumulus is still under debate [Humphris et al, 1990]…”

Introduction

“…It has a simple, t/-shaped form and is underlain by fissured and block-faulted basaltic pillow lavas and numerous small conical volcanic structures (Kong et al, 1988;Brown and Karson, 1988;Humphris et al, 1990). Near the center of this segment lies Serocki Volcano (ODP Leg 106 Scientific Party, 1986; Site 648).…”

“…As suggested by Klein and Langmuir (1987), the Na (8 0) (the "corrected" value of Na 2 O to 8.0 wt% MgO) and CaO (8 0 /Al 2 O 3(8 0) value (similarly recast to 8.0 wt% MgO) in basalt glasses can be used as a measure of the extent of mantle melting or depletion in the midocean ridge basalt (MORB) source. The value of Na (8 0) in the MARK area glasses varies between 2.6 and 3.1, and with the exception of several high-alumina basalts, the CaO (8 0 /Al 2 O 3(8 0) value of basalts varies between 6.8 and 7.3 (Humphris et al, 1990;Langmuir et al, 1992;Bryan et al, 1994;Casey et al, unpubl. data).…”

“…Basalts from this region also have relatively unradiogenic Pb-isotope compositions (Kempton et al, 1993). Trace element data suggest that most MARK basalts are light rare earth element (REE) depleted, typical of N-MORB Humphris et al, 1990) with a few exceptions that tend to exhibit flat REE patterns and can be classified as transition-MORB (T-MORB) (Casey and Bryan, unpubl. data).…”