Direct measurements of oceanic crustal density at the northern Juan de Fuca Ridge

Citation
La. Gilbert et Hp. Johnson, Direct measurements of oceanic crustal density at the northern Juan de Fuca Ridge, GEOPHYS R L, 26(24), 1999, pp. 3633-3636
Citations number
29
Categorie Soggetti
Earth Sciences
Journal title
GEOPHYSICAL RESEARCH LETTERS
ISSN journal
00948276 → ACNP
Volume
26
Issue
24
Year of publication
1999
Pages
3633 - 3636
Database
ISI
SICI code
0094-8276(199912)26:24<3633:DMOOCD>2.0.ZU;2-9
Abstract
Density and porosity of oceanic crust are critically important to understan ding the circulation of hydrothermal fluid at mid-ocean ridges. To determin e these parameters directly, we completed a fixed, on-bottom gravity survey on the Endeavour Segment of the Juan de Fuca Ridge, which is a well studie d spreading center that is both hydrothermally and tectonically active. A B ell-Aerospace gravity meter mounted within the submersible ALVIN was used t o make gravity measurements from the floor of the axial valley to the summi t of the west axial ridge. Analysis of these data gave a density of 2240+/- 50 kg/m(3) for the upper 130 m of crust. Comparison of the outcrop density with that of recovered rock samples resulted in a calculated porosity of 38 +/-4%. Forward modeling of the seafloor gravity data indicated that both th e valley floor and bounding walls have unusually low density crust that is flanked by higher density crust.