Title:
 Petrogenesis of Pre-caldera mafic lavas, Jemez Mountains volcanic field 
Reference Number:
 8804 
ISSN:
 0022-3530
Publication Year:
 2005
GeoREF Number:
 2005-047432 (View Original Data File)
Authors:
 Wolff, J.A.; Rowe, M.C.; Teasdale, R.; Gardner, J.N.; Ramos, F.C.; Heikoop, C.E.
Descriptors:
 assimilation, Cenozoic, depletion, Jemez Lineament, Jemez Mountains, Jemez Mountains volcanic field, lava, mafic composition, magma contamination, magmas, Miocene, Neogene, New Mexico, partial melting, Quaternary, Rio Grande, Tertiary, United States, Valles Caldera
Source:
 Journal of Petrology, vol.46, no.2, pp.407-439, Sept 2005
Abstract:
 The Miocene-Quaternary Jemez Mountains volcanic field (JMVF), the site of the Valles caldera, lies at the intersection of the Jemez lineament, a Proterozoic suture, and the Cenozoic Rio Grande rift. Parental magmas are of two types: K-depleted silica-undersaturated, derived from the partial melting of lithospheric mantle with residual amphibole, and tholeiitic, derived from either asthenospheric or lithospheric mantle. Variability in silica-undersaturated basalts reflects contributions of melts derived from lherzolitic and pyroxenitic mantle, representing heterogeneous lithosphere associated with the suture. The K depletion is inherited by fractionated, crustally contaminated derivatives (hawaiites and mugearites), leading to distinctive incompatible trace element signatures, with Th/(Nb,Ta) and La/(Nb,Ta) greater than, but K/(Nb,Ta) similar to, Bulk Silicate Earth. These compositions dominate the mafic and intermediate lavas, and the JMVF is therefore derived largely, and perhaps entirely, from melting of fertile continental Jemez lineament lithosphere during rift-related extension. Significant variations in Pb and Nd isotope ratios ( (super 206) Pb/ (super 204) Pb = 17.20-18.93; (super 143) Nd/ (super 144) Nd = 0.51244-0.51272) result from crustal contamination, whereas 87Sr/86Sr is low and relatively uniform (0.7040-0.7048). We compare the effects of contamination by low- (super 87) Sr/ (super 86) Sr crust with assimilation of high- (super 87) Sr/ (super 86) Sr granitoid by partial melting, with Sr retained in a feldspathic residue. Both models satisfactorily reproduce the isotopic features of the rocks, but the lack of a measurable Eu anomaly in most JMVF mafic lavas is difficult to reconcile with a major role for residual plagioclase during petrogenesis.
Copyright:
 GeoRef, Copyright 2008, American Geological Institute.

Sample Summary:
Sample ID: Major Data: Trace Data: Isotope Data:
JM93141 Yes Yes No
JM03-9A Yes Yes No
JM93137- Yes Yes No
JM93176 Yes Yes Yes
JM93135A Yes Yes Yes
JM93252 Yes Yes Yes
JM93198 Yes Yes Yes
JM93232 Yes Yes Yes
JM9350-2 Yes Yes Yes
JM93233 Yes Yes Yes
JM9325 Yes Yes Yes
JM93262 Yes Yes Yes
JM93125 Yes Yes Yes
MR0047 Yes Yes No
MR0013 Yes Yes Yes
MR0076 Yes Yes Yes
JW001-1 Yes Yes No
JW144-4 Yes Yes No
JW144-10 Yes Yes No
JW144-12 Yes Yes No
JW144-16 Yes Yes No
JW144-20 Yes Yes No
JW238-1 Yes Yes No
MR00-9 Yes Yes Yes
MR00-7 Yes Yes Yes
SF-1 Yes Yes No
SF-9 Yes Yes No
O-1 Yes Yes No
PL Yes Yes No
I-6 Yes Yes Yes
I-3 Yes Yes No
H-0 Yes Yes No
SF-3 Yes Yes Yes
I-5 Yes Yes Yes
WR1 Yes Yes No
EA3 Yes Yes No
EA4 Yes Yes No
EA6 Yes Yes No
EA8 Yes Yes No
EA9 Yes Yes No
EA11 Yes Yes No