Excess argon in amphiboles linked to greenschist facies alteration in the Kamila amphibolite belt, Kohistan island arc system, northern Pakistan; insights from 40Ar/39Ar step-heating and acid leaching experiments

Saved in:
Authors:Wartho, J. A.; Rex, D. C.; Guise, P. G.
Author Affiliations:Primary:
University of Leeds, Leeds, United Kingdom
Volume Title:Geological Magazine
Source:Geological Magazine, 133(5), p.595-609. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568
Publication Date:1996
Note:In English. 56 refs.; illus., incl. 3 tables, geol. sketch map
Summary:A mineralogical and 40Ar/39Ar study of 13 hornblendes from the Kamila amphibolite belt and Kamila shear zone in N Pakistan has revealed a correlation between the degree of greenschist-facies alteration and quantity of excess 40Ar. There is also a N-S divide, with amphibole from the N region showing greater degrees of greenschist-facies alteration, brittle deformation and excess 40Ar incorporation compared to the predominantly plastically deformed, less altered amphibole samples from the Kamila shear zone in the S. Acid leaching of two hornblendes from the Kamila amphibolite belt indicates that a large proportion of the excess 40Ar is correlated with later greenschist-facies alteration phases, and can be easily removed by acid etching, thus revealing acceptable regional 40Ar/39Ar plateau ages of ∼ 76 ± 4 m.y. [R.A.H.]
Subjects:Absolute age; Alteration; Amphibolites; Ar/Ar; Argon; Brittle deformation; Cretaceous; Dates; Deformation; Facies; Greenschist facies; Isotope ratios; Isotopes; Mesozoic; Metamorphic rocks; Metavolcanic rocks; Noble gases; Radioactive isotopes; Stable isotopes; Asia; Indian Peninsula; Indus Valley; Kohistan; Pakistan; Kamila amphibolite belt; Kamila shear zone; Northern Pakistan
Abstract Numbers:97M/1808
Record ID:1997010791
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Tags: Add Tag
No Tags, Be the first to tag this record!
LEADER 03472naaaa2200625zu 4500
001 1997010791
003 ViAlAGI
005 20190221172418.0
008 190110e199609 xxka 0 0 eng d
040 |a ViAlAGI  |c ViAlAGI 
072 7 |a 03  |2 georeft 
072 7 |a 05A  |2 georeft 
100 1 |a Wartho, J. A.  |e analytic author  |u University of Leeds, Leeds 
245 1 0 |a Excess argon in amphiboles linked to greenschist facies alteration in the Kamila amphibolite belt, Kohistan island arc system, northern Pakistan; insights from >40`Ar/>39`Ar step-heating and acid leaching experiments 
300 |a p. 595-609 
500 |a In English. 56 refs. 
500 |a Abstract number: 97M/1808 
500 |a Abstractor: R.A.H. 
500 |a Affiliation: University of Leeds; Leeds; GBR; United Kingdom 
500 |a Key title: Geological Magazine 
500 |a Source note: Geological Magazine, 133(5), p.595-609. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568 
500 |a Publication type: journal article 
504 |b 56 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom 
520 |a A mineralogical and >40`Ar/>39`Ar study of 13 hornblendes from the Kamila amphibolite belt and Kamila shear zone in N Pakistan has revealed a correlation between the degree of greenschist-facies alteration and quantity of excess >40`Ar. There is also a N-S divide, with amphibole from the N region showing greater degrees of greenschist-facies alteration, brittle deformation and excess >40`Ar incorporation compared to the predominantly plastically deformed, less altered amphibole samples from the Kamila shear zone in the S. Acid leaching of two hornblendes from the Kamila amphibolite belt indicates that a large proportion of the excess >40`Ar is correlated with later greenschist-facies alteration phases, and can be easily removed by acid etching, thus revealing acceptable regional >40`Ar/>39`Ar plateau ages of ∼ 76 ± 4 m.y. 
650 7 |a Absolute age  |2 georeft 
650 7 |a Alteration  |2 georeft 
650 7 |a Amphibolites  |2 georeft 
650 7 |a Ar/Ar  |2 georeft 
650 7 |a Argon  |2 georeft 
650 7 |a Brittle deformation  |2 georeft 
650 7 |a Cretaceous  |2 georeft 
650 7 |a Dates  |2 georeft 
650 7 |a Deformation  |2 georeft 
650 7 |a Facies  |2 georeft 
650 7 |a Greenschist facies  |2 georeft 
650 7 |a Isotope ratios  |2 georeft 
650 7 |a Isotopes  |2 georeft 
650 7 |a Mesozoic  |2 georeft 
650 7 |a Metamorphic rocks  |2 georeft 
650 7 |a Metavolcanic rocks  |2 georeft 
650 7 |a Noble gases  |2 georeft 
650 7 |a Radioactive isotopes  |2 georeft 
650 7 |a Stable isotopes  |2 georeft 
651 7 |a Asia  |2 georeft 
651 7 |a Indian Peninsula  |2 georeft 
651 7 |a Indus Valley  |2 georeft 
651 7 |a Kohistan  |2 georeft 
651 7 |a Pakistan  |2 georeft 
653 |a Kamila amphibolite belt 
653 |a Kamila shear zone 
653 |a Northern Pakistan 
700 1 |a Rex, D. C.,  |e analytic author 
700 1 |a Guise, P. G.,  |e analytic author 
773 0 |t Geological Magazine  |d London : Cambridge University Press, Sep. 1996  |x 0016-7568  |y GEMGA4  |n Geological Magazine, 133(5), p.595-609. Publisher: Cambridge University Press, London, United Kingdom. ISSN: 0016-7568 Publication type: journal article  |g Vol. 133, no. 5  |h illus., incl. 3 tables, geol. sketch map