Computer Science
Scientific paper
Apr 1978
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1978e%26psl..39..281m&link_type=abstract
Earth and Planetary Science Letters, Volume 39, Issue 2, p. 281-290.
Computer Science
11
Scientific paper
A combination of data from two isotopic systems may be useful in ``seeing through'' an intense metamorphic event to the primary age of an ancient terrane. Rb-Sr secondary isochrons on thin-slice samples make it possible to select domains within the rock in which Sr isotopes were equilibrated during the high-temperature stage of the metamorphism. A single domain may then be tested for Pb isotopic homogeneity at the same time by use of secondary U-Pb isochrons. These monitor the possible effect of recent U loss, and if successful yield values for the common Pb ratios at the time of the thermal event. If the thermal event is both ancient and well-dated by the secondary isochrons, a model age for the protolith may then be established. The method is illustrated here with reference to the Imataca Series, about which we conclude the following: s(1)|The primary or protolith age of the Imataca Series is in the range of 3.4-3.7 b.y. s(2)|At approximately 2 b.y. ago, a regional metamorphic event up to granulite grade in intensity affected the Imataca. s(3)|This metamorphism was accompanied by complete local homogenization of Sr isotopes over distances of centimeters; equilibration of Pb isotopes was apparently less perfect at the same scale. s(4)|The granulite event was further characterized by extensive depletion of U relative to Pb. Comparable Rb loss has not taken place, perhaps because of the abundance of K-bearing phases. s(5)|Deformation of the rock unit investigated may have taken the form of separate shear surfaces, between which isotopically equilibrated domains on either side of a shear plane are identified by differences in initial Sr isotope ratio.
Hurley Patrick M.
Montgomery Carla W.
No associations
LandOfFree
Total-rock U-Pb and Rb-Sr systematics in the Imataca Series, Guayana Shield, Venezuela does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Total-rock U-Pb and Rb-Sr systematics in the Imataca Series, Guayana Shield, Venezuela, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Total-rock U-Pb and Rb-Sr systematics in the Imataca Series, Guayana Shield, Venezuela will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1379671