%0 Journal Article
%T Olivine-hornblende-lamprophyre dikes from Quebrada los Sapos, El Teniente, Central Chile (34¡ãS): implications for the temporal geochemical evolution of the Andean subarc mantle
%A Stern
%A Charles R
%A Floody
%A Ricardo
%A Espi£¿e¨ªra
%A Domingo
%J Andean geology
%D 2011
%I Scientific Electronic Library Online
%X mafic mg-olivine (fo88)4-hornblende lamprophyre dikes, with ni -190 ppm and cr -390 ppm, cut late miocene lavas in the quebrada los sapos a few kilometers west of the el teniente cu-mo mine. these dikes have petro-chemical affinities with other less primitive, pliocene (2.9-3.9 ma), olivine-free lamprophyres previously described from both within and in the vicinity of el teniente. the mafic mantle-derived lamprophyre dikes from quebrada los sapos have la/yb ratios of 10-13, higher than the ratios of 4-9 for older late miocene el teniente mafic complex olivine basalts, suggesting a temporal decrease in the percent of partial mantle melting, consistent with the observed decrease in the volume of igneous rocks through time at this latitude, as well as the ult¨ªmate cessation of magmatism and >40 km eastward are migration by the late pliocene. less primitive olivine-free lamprophyres have higher la and lower yb, resulting in higher la/yb ratios of 15-44, due to crystal-liquid fractionation involving hornblende, but not plagioclase, the crystallization of which is suppressed by the high h2o contents of the lamprophyres. the lamprophyre dikes, as well as younger (1.8-2.3 ma) olivine-bearing basaltic-andesite lava flows in the valley of the cachapoal river, have 87sr/86sr=0.7041 to 0.7049, =+1.2 to -1.1 and 206pb/204pb=18.60 to 18.68, while middle to late miocene (6.5-13.9 ma) el teniente volcanic and plutonic complex igneous rocks have lower 87sr/86sr=0.7039 to 0.7041 and 206pb/204pb=18.56 to 18.59, and higher g =+1.9 to +3.8, and older oligocene to early miocene (>15 ma) abanico or coya-machal¨ª formation volcanic and plutonic rocks in the region have even lower 87sr/86sr=0.7033 to 0.7039 and 206pb/204pb=18.45 to 18.57, and higher gnd=+3.8 to +6.2. the data indicate a significant progressive temporal evolution, between the oligocene and the pliocene, to higher 87sr/86sr and 206pb/204pb, and lower for mantle-derived mafic magmas, and by implication their mantle source regio
%K el teniente cu-deposit
%K lamprophyres
%K subduction erosion
%K subarc mantle
%K isotopes.
%U http://www.scielo.cl/scielo.php?script=sci_abstract&pid=S0718-71062011000100001&lng=en&nrm=iso&tlng=en