thumbnail

Multiple age components in individual molybdenite grains

Chemical Geology

By:
, , , ,
DOI: 10.1016/j.chemgeo.2012.01.011

Links

Abstract

Re–Os geochronology of fractions composed of unsized, coarse, and fine molybdenite from a pod of unusual monazite–xenotime gneiss within a granulite facies paragneiss, Hudson Highlands, NY, yielded dates of 950.5 ± 2.5, 953.8 ± 2.6, and 941.2 ± 2.6 Ma, respectively. These dates are not recorded by co-existing zircon, monazite, or xenotime. SEM–BSE imagery of thin sections and separated grains reveals that most molybdenite grains are composed of core and rim plates that are approximately perpendicular. Rim material invaded cores, forming irregular contacts, probably reflecting dissolution/reprecipitation. EPMA and LA-ICP-MS analyses show that cores and rims have different trace element concentrations (for example, cores are relatively enriched in W). On the basis of inclusions of zircon with metamorphic overgrowths, we conclude that molybdenite cores and rims formed after high-grade regional metamorphism. The discovery of cores and rims in individual molybdenite grains is analogous to multi-component U-Pb geochronometers such as zircon, monazite, and titanite; thus, molybdenite should be carefully examined before dating to ensure that the requirement of age homogeneity is fulfilled.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Multiple age components in individual molybdenite grains
Series title:
Chemical Geology
DOI:
10.1016/j.chemgeo.2012.01.011
Volume
300-301
Year Published:
2012
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Central Mineral and Environmental Resources Science Center
Description:
6 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
55
Last page:
60
Country:
United States
State:
New York