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Mafic magmatism in the Bakhuis Granulite Belt (western Suriname) : relationship with charnockite magmatism and UHT metamorphism

Klaver, Martijn; de Roever, Emond W F; Thijssen, Antonia C D; Bleeker, Wouter; Söderlund, Ulf LU ; Chamberlain, Kevin; Ernst, Richard; Berndt, Jasper and Zeh, Armin (2016) In GFF 138(1). p.203-218
Abstract

The Bakhuis Granulite Belt (BGB) is a metamorphic terrain within the Guiana Shield that experienced ultrahigh-temperature (UHT) metamorphism at 2.07–2.05Ga. In the southwest of the BGB, the Kabalebo charnockites were emplaced at ca. 1.99Ga and thus postdate UHT metamorphism by at least 60Myr. Two generations of gabbroic intrusions have been recognized within the BGB, which could act as a heat source for the two UHT events. A younger generation of tholeiitic “Charlie” gabbros yields a baddeleyite U/Pb age of 1971±15Ma. The presence of a metamorphic overprint indicates that the hornblende-bearing “Moi–Moi” metagabbros predate the Charlie gabbros. Large zircons with complex zoning patterns are found in a Moi–Moi metagabbro sample. The main... (More)

The Bakhuis Granulite Belt (BGB) is a metamorphic terrain within the Guiana Shield that experienced ultrahigh-temperature (UHT) metamorphism at 2.07–2.05Ga. In the southwest of the BGB, the Kabalebo charnockites were emplaced at ca. 1.99Ga and thus postdate UHT metamorphism by at least 60Myr. Two generations of gabbroic intrusions have been recognized within the BGB, which could act as a heat source for the two UHT events. A younger generation of tholeiitic “Charlie” gabbros yields a baddeleyite U/Pb age of 1971±15Ma. The presence of a metamorphic overprint indicates that the hornblende-bearing “Moi–Moi” metagabbros predate the Charlie gabbros. Large zircons with complex zoning patterns are found in a Moi–Moi metagabbro sample. The main growth domains of these zircons give an age of 1984±4Ma, which is indistinguishable from the surrounding charnockites. Matching trace element and Hf isotope characteristics indicate that the complex zircons are derived from the charnockites. We argue that the emplacement of the metagabbros and charnockite magmatism were contemporaneous and that zircon grains from the charnockitic melt were mechanically transferred to the gabbroic bodies during magma mingling. The new ages for the gabbroic bodies in the BGB confirm that they are contemporaneous with, and the likely heat source for, charnockite magmatism, but that they are not associated with the 2.07–2.05Ga UHT event. Furthermore, the new ages and recognition of the Moi–Moi metagabbros as an Alaskan-type complex provide the first direct evidence for late Transamazonian subduction zone magmatism in the Guiana Shield.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bakhuis Granulite Belt, geochronology, Guiana Shield, metagabbro, zircon geochemistry
in
GFF
volume
138
issue
1
pages
16 pages
publisher
Geological Society of Sweden
external identifiers
  • Scopus:84959152046
ISSN
1103-5897
DOI
10.1080/11035897.2015.1061591
language
English
LU publication?
yes
id
032076b7-9e87-4e25-8c7e-d79a28901f19
date added to LUP
2016-09-21 08:26:13
date last changed
2016-11-09 08:24:21
@misc{032076b7-9e87-4e25-8c7e-d79a28901f19,
  abstract     = {<p>The Bakhuis Granulite Belt (BGB) is a metamorphic terrain within the Guiana Shield that experienced ultrahigh-temperature (UHT) metamorphism at 2.07–2.05Ga. In the southwest of the BGB, the Kabalebo charnockites were emplaced at ca. 1.99Ga and thus postdate UHT metamorphism by at least 60Myr. Two generations of gabbroic intrusions have been recognized within the BGB, which could act as a heat source for the two UHT events. A younger generation of tholeiitic “Charlie” gabbros yields a baddeleyite U/Pb age of 1971±15Ma. The presence of a metamorphic overprint indicates that the hornblende-bearing “Moi–Moi” metagabbros predate the Charlie gabbros. Large zircons with complex zoning patterns are found in a Moi–Moi metagabbro sample. The main growth domains of these zircons give an age of 1984±4Ma, which is indistinguishable from the surrounding charnockites. Matching trace element and Hf isotope characteristics indicate that the complex zircons are derived from the charnockites. We argue that the emplacement of the metagabbros and charnockite magmatism were contemporaneous and that zircon grains from the charnockitic melt were mechanically transferred to the gabbroic bodies during magma mingling. The new ages for the gabbroic bodies in the BGB confirm that they are contemporaneous with, and the likely heat source for, charnockite magmatism, but that they are not associated with the 2.07–2.05Ga UHT event. Furthermore, the new ages and recognition of the Moi–Moi metagabbros as an Alaskan-type complex provide the first direct evidence for late Transamazonian subduction zone magmatism in the Guiana Shield.</p>},
  author       = {Klaver, Martijn and de Roever, Emond W F and Thijssen, Antonia C D and Bleeker, Wouter and Söderlund, Ulf and Chamberlain, Kevin and Ernst, Richard and Berndt, Jasper and Zeh, Armin},
  issn         = {1103-5897},
  keyword      = {Bakhuis Granulite Belt,geochronology,Guiana Shield,metagabbro,zircon geochemistry},
  language     = {eng},
  month        = {01},
  number       = {1},
  pages        = {203--218},
  publisher    = {ARRAY(0xd6cbe70)},
  series       = {GFF},
  title        = {Mafic magmatism in the Bakhuis Granulite Belt (western Suriname) : relationship with charnockite magmatism and UHT metamorphism},
  url          = {http://dx.doi.org/10.1080/11035897.2015.1061591},
  volume       = {138},
  year         = {2016},
}