U-Pb studies of zircon cores and overgrowths, and monazite: implications for age and petrogenesis of the northeastern Idaho batholith.

M. E. Bickford, R. B. Chase, B. K. Nelson, R. D. Shuster, E. C. Arruda

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

U/Pb isotopic studies of zircons, many containing xenocrystic cores with euhedral overgrowths, and monazite from igneous rocks and metasedimentary inclusions of the northeastern Idaho batholith yield linear arrays on concordia diagrams. We interpret these as mixing lines between an old component (cores) and a young component (overgrowths and zircons without cores). The lower intercept of such arrays with concordia may yield the minimum age of the rocks if the overgrowths and zircons without cores are discordant, or the crystallization age if they are concordant. Monazites yield apparently concordant ages either equal or less than the lower intercept zircon ages. The samples studied yield lower intercept ages ranging from 73.5+ or -6 Ma (foliated quartz diorite) to 46.5+ or -1 Ma (feldspar megacryst granite); ages obtained are consistent with crosscutting relations observed in the field. Upper intercepts yield ages of 1700 to 2349 Ma. These are interpreted to indicate the mean age of xenocrystic zircon. Studies of zircons from xenolith suites indicate that they could represent the source of the old zircon component. The zircon and monazite results, the generally high initial 87Sr/86Sr ratios of the igneous rocks, and the isotopic composition of Pb in feldspar indicate that the magmas were derived anatectically from a continental crustal source or were extensively mixed with such old crust prior to or during emplacement.-Authors

Original languageEnglish (US)
Pages (from-to)433-457
Number of pages25
JournalJournal of Geology
Volume89
Issue number4
DOIs
StatePublished - Jan 1 1981

Fingerprint

monazite
batholith
petrogenesis
zircon
igneous rock
feldspar
megacryst
xenolith
diorite
emplacement
isotopic composition
crystallization
granite
diagram
crust
quartz
rock

ASJC Scopus subject areas

  • Geology

Cite this

U-Pb studies of zircon cores and overgrowths, and monazite : implications for age and petrogenesis of the northeastern Idaho batholith. / Bickford, M. E.; Chase, R. B.; Nelson, B. K.; Shuster, R. D.; Arruda, E. C.

In: Journal of Geology, Vol. 89, No. 4, 01.01.1981, p. 433-457.

Research output: Contribution to journalArticle

@article{5078882ba81e40af8280af2a9cc1ea3e,
title = "U-Pb studies of zircon cores and overgrowths, and monazite: implications for age and petrogenesis of the northeastern Idaho batholith.",
abstract = "U/Pb isotopic studies of zircons, many containing xenocrystic cores with euhedral overgrowths, and monazite from igneous rocks and metasedimentary inclusions of the northeastern Idaho batholith yield linear arrays on concordia diagrams. We interpret these as mixing lines between an old component (cores) and a young component (overgrowths and zircons without cores). The lower intercept of such arrays with concordia may yield the minimum age of the rocks if the overgrowths and zircons without cores are discordant, or the crystallization age if they are concordant. Monazites yield apparently concordant ages either equal or less than the lower intercept zircon ages. The samples studied yield lower intercept ages ranging from 73.5+ or -6 Ma (foliated quartz diorite) to 46.5+ or -1 Ma (feldspar megacryst granite); ages obtained are consistent with crosscutting relations observed in the field. Upper intercepts yield ages of 1700 to 2349 Ma. These are interpreted to indicate the mean age of xenocrystic zircon. Studies of zircons from xenolith suites indicate that they could represent the source of the old zircon component. The zircon and monazite results, the generally high initial 87Sr/86Sr ratios of the igneous rocks, and the isotopic composition of Pb in feldspar indicate that the magmas were derived anatectically from a continental crustal source or were extensively mixed with such old crust prior to or during emplacement.-Authors",
author = "Bickford, {M. E.} and Chase, {R. B.} and Nelson, {B. K.} and Shuster, {R. D.} and Arruda, {E. C.}",
year = "1981",
month = "1",
day = "1",
doi = "10.1086/628607",
language = "English (US)",
volume = "89",
pages = "433--457",
journal = "Journal of Geology",
issn = "0022-1376",
publisher = "University of Chicago",
number = "4",

}

TY - JOUR

T1 - U-Pb studies of zircon cores and overgrowths, and monazite

T2 - implications for age and petrogenesis of the northeastern Idaho batholith.

AU - Bickford, M. E.

AU - Chase, R. B.

AU - Nelson, B. K.

AU - Shuster, R. D.

AU - Arruda, E. C.

PY - 1981/1/1

Y1 - 1981/1/1

N2 - U/Pb isotopic studies of zircons, many containing xenocrystic cores with euhedral overgrowths, and monazite from igneous rocks and metasedimentary inclusions of the northeastern Idaho batholith yield linear arrays on concordia diagrams. We interpret these as mixing lines between an old component (cores) and a young component (overgrowths and zircons without cores). The lower intercept of such arrays with concordia may yield the minimum age of the rocks if the overgrowths and zircons without cores are discordant, or the crystallization age if they are concordant. Monazites yield apparently concordant ages either equal or less than the lower intercept zircon ages. The samples studied yield lower intercept ages ranging from 73.5+ or -6 Ma (foliated quartz diorite) to 46.5+ or -1 Ma (feldspar megacryst granite); ages obtained are consistent with crosscutting relations observed in the field. Upper intercepts yield ages of 1700 to 2349 Ma. These are interpreted to indicate the mean age of xenocrystic zircon. Studies of zircons from xenolith suites indicate that they could represent the source of the old zircon component. The zircon and monazite results, the generally high initial 87Sr/86Sr ratios of the igneous rocks, and the isotopic composition of Pb in feldspar indicate that the magmas were derived anatectically from a continental crustal source or were extensively mixed with such old crust prior to or during emplacement.-Authors

AB - U/Pb isotopic studies of zircons, many containing xenocrystic cores with euhedral overgrowths, and monazite from igneous rocks and metasedimentary inclusions of the northeastern Idaho batholith yield linear arrays on concordia diagrams. We interpret these as mixing lines between an old component (cores) and a young component (overgrowths and zircons without cores). The lower intercept of such arrays with concordia may yield the minimum age of the rocks if the overgrowths and zircons without cores are discordant, or the crystallization age if they are concordant. Monazites yield apparently concordant ages either equal or less than the lower intercept zircon ages. The samples studied yield lower intercept ages ranging from 73.5+ or -6 Ma (foliated quartz diorite) to 46.5+ or -1 Ma (feldspar megacryst granite); ages obtained are consistent with crosscutting relations observed in the field. Upper intercepts yield ages of 1700 to 2349 Ma. These are interpreted to indicate the mean age of xenocrystic zircon. Studies of zircons from xenolith suites indicate that they could represent the source of the old zircon component. The zircon and monazite results, the generally high initial 87Sr/86Sr ratios of the igneous rocks, and the isotopic composition of Pb in feldspar indicate that the magmas were derived anatectically from a continental crustal source or were extensively mixed with such old crust prior to or during emplacement.-Authors

UR - http://www.scopus.com/inward/record.url?scp=0019727003&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0019727003&partnerID=8YFLogxK

U2 - 10.1086/628607

DO - 10.1086/628607

M3 - Article

AN - SCOPUS:0019727003

VL - 89

SP - 433

EP - 457

JO - Journal of Geology

JF - Journal of Geology

SN - 0022-1376

IS - 4

ER -