GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC)
The geochemistry of 203 fresh, glassy, zero-age basalts dredged from along the 500 km long Juan de Fuca Ridge (JDFR) illustrates the unique and complex behavior of this active spreading center located on the northern end of the East Pacific Rise. The Cobb-Eickelberg Seamount chain, the trace of the...
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ftunivmassamh:oai:scholarworks.umass.edu:dissertations-2579 2023-05-15T16:51:39+02:00 GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) LIIAS, RAIMO ARNOLD 1986-01-01T08:00:00Z https://scholarworks.umass.edu/dissertations/AAI8622692 ENG eng ScholarWorks@UMass Amherst https://scholarworks.umass.edu/dissertations/AAI8622692 Doctoral Dissertations Available from Proquest Geochemistry text 1986 ftunivmassamh 2022-01-09T20:05:20Z The geochemistry of 203 fresh, glassy, zero-age basalts dredged from along the 500 km long Juan de Fuca Ridge (JDFR) illustrates the unique and complex behavior of this active spreading center located on the northern end of the East Pacific Rise. The Cobb-Eickelberg Seamount chain, the trace of the Cobb hot spot, intersects the JDFR at 46(DEGREES)N, where a young, volcanically active seamount, astride the ridge, gives clear evidence for continuing hot spot activity. In contrast with other well-documented mantle plume - ridge intersections (eg. Iceland, Azores, Galapagos), there are no systematic geochemical gradients away from the center of maximum volcanism. Petrographic and major element evidence indicates that most JDFR basalts are normal 'depleted' mid-ocean ridge basalts (MORB). However, unlike the vast majority of MORB, the trace element ratios along the JDFR, although highly variable on the scale of single dredge hauls, are predominantly transitional (Zr/Nb = 22) between depleted MORB (Zr/Nb greater than 40) and enriched oceanic island (or plume) basalts (Zr/Nb = 10). North of the Cobb Fracture Zone at 48(DEGREES)N, the Endeavour segment is chemically distinct from the rest of the JDFR with uniformly enriched trace and rare earth element ratios (Zr/Nb 7-15, La/Sm(, ch ) greater than 1). Geochemical variability observed along the JDFR requires a heterogeneous mantle source for JDFR basalts. Transitional trace element ratios can be explained by regionally extensive mixing of enriched (Endeavour-like) and more normal MORB magmas, however, this mixing is not simple, two component mixing. Highly evolved basalts, (Fe(,2)O(,3)* greater than 12.0 wt.%, TiO(,2) greater than 2.0 wt.%) resulting from extensive crystal fractionation requires this mixing be sporadic. Text Iceland University of Massachusetts: ScholarWorks@UMass Amherst Endeavour ENVELOPE(162.000,162.000,-76.550,-76.550) Galapagos Pacific |
institution |
Open Polar |
collection |
University of Massachusetts: ScholarWorks@UMass Amherst |
op_collection_id |
ftunivmassamh |
language |
English |
topic |
Geochemistry |
spellingShingle |
Geochemistry LIIAS, RAIMO ARNOLD GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
topic_facet |
Geochemistry |
description |
The geochemistry of 203 fresh, glassy, zero-age basalts dredged from along the 500 km long Juan de Fuca Ridge (JDFR) illustrates the unique and complex behavior of this active spreading center located on the northern end of the East Pacific Rise. The Cobb-Eickelberg Seamount chain, the trace of the Cobb hot spot, intersects the JDFR at 46(DEGREES)N, where a young, volcanically active seamount, astride the ridge, gives clear evidence for continuing hot spot activity. In contrast with other well-documented mantle plume - ridge intersections (eg. Iceland, Azores, Galapagos), there are no systematic geochemical gradients away from the center of maximum volcanism. Petrographic and major element evidence indicates that most JDFR basalts are normal 'depleted' mid-ocean ridge basalts (MORB). However, unlike the vast majority of MORB, the trace element ratios along the JDFR, although highly variable on the scale of single dredge hauls, are predominantly transitional (Zr/Nb = 22) between depleted MORB (Zr/Nb greater than 40) and enriched oceanic island (or plume) basalts (Zr/Nb = 10). North of the Cobb Fracture Zone at 48(DEGREES)N, the Endeavour segment is chemically distinct from the rest of the JDFR with uniformly enriched trace and rare earth element ratios (Zr/Nb 7-15, La/Sm(, ch ) greater than 1). Geochemical variability observed along the JDFR requires a heterogeneous mantle source for JDFR basalts. Transitional trace element ratios can be explained by regionally extensive mixing of enriched (Endeavour-like) and more normal MORB magmas, however, this mixing is not simple, two component mixing. Highly evolved basalts, (Fe(,2)O(,3)* greater than 12.0 wt.%, TiO(,2) greater than 2.0 wt.%) resulting from extensive crystal fractionation requires this mixing be sporadic. |
format |
Text |
author |
LIIAS, RAIMO ARNOLD |
author_facet |
LIIAS, RAIMO ARNOLD |
author_sort |
LIIAS, RAIMO ARNOLD |
title |
GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
title_short |
GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
title_full |
GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
title_fullStr |
GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
title_full_unstemmed |
GEOCHEMISTRY AND PETROGENESIS OF BASALTS ERUPTED ALONG THE JUAN DE FUCA RIDGE (PACIFIC) |
title_sort |
geochemistry and petrogenesis of basalts erupted along the juan de fuca ridge (pacific) |
publisher |
ScholarWorks@UMass Amherst |
publishDate |
1986 |
url |
https://scholarworks.umass.edu/dissertations/AAI8622692 |
long_lat |
ENVELOPE(162.000,162.000,-76.550,-76.550) |
geographic |
Endeavour Galapagos Pacific |
geographic_facet |
Endeavour Galapagos Pacific |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Doctoral Dissertations Available from Proquest |
op_relation |
https://scholarworks.umass.edu/dissertations/AAI8622692 |
_version_ |
1766041771240849408 |