Socorro Island (18$\sp\circ$45'N, 111$\sp\circ$00'W) is the top portion of Volcan Evermann which has recorded historic eruptions in 1848 (?), 1896 (?), 1947, 1951 and 1993. The volcano is located at the intersection of the Clarion Fracture Zone (E-W) and the Mathematician Ridge System (N-S), and has erupted voluminous (i.e. 36 km$\sp3)$ pantellerite to trachyte ash-flows, lava-flows and domes which make up for 90% of the rocks exposed on the island. The southeastern portion of Socorro Island, known as the Lomas Coloradas area, makes up for the remaining 10%, and consists mostly of pahoehoe lava-flows of subalkaline basalt, mugearite and hawaiite intercalated with horizons of ash and scoria erupted from numerous cinder cones. K/Ar ages of the peralkaline rocks and the Lomas Coloradas basalts cluster around 0.5 m.y. suggesting eruption rates one order of magnitude larger than those estimated for Pantelleria, Italy. Although the evolution of peralkaline rocks at Pantelleria has been explained by partial melting of an alkali gabbro, mineralogical and geochemical data presented in this study are more consistent with a mechanism of differentiation involving crystal fractionation and possibly volatile-transfer from a parental basalt magma. The model proposed here has no constraints in terms of the volumes of magmas involved since the submerged portion of Volcan Evermann is presumed to be made entirely of basalt. The tectonic setting of Volcan Evermann and the eruption of volatile-rich voluminous pyroclastic-flows are considered as important factors in the development of the peralkaline condition at Socorro Island and the lack of Daly gap intermediates common to other oceanic islands of peralkaline affinity / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_25201 |
| Date | January 1994 |
| Contributors | Carballido-Sanchez, Enrique Alberto (Author), Nelson, Stephen A (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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