Age and nature of carbonatite emplacement in North Pakistan

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Authors:Le Bas, M. J.; Mian, I.; Rex, D. C.
Author Affiliations:Primary:
Univ. Leicester, Dep. Geol., GB-Leicester LE1 7RH, United Kingdom
Volume Title:Geologische Rundschau
Source:Geologische Rundschau, 76(2), p.317-323. Publisher: Springer International, Berlin, Federal Republic of Germany. ISSN: 0016-7835
Publication Date:1987
Note:In English with German and French and Russian summaries. 15 refs.; illus. incl. 3 tables, charts, sects., geol. sketch maps, sketch map
Summary:The N Pakistan carbonatites of Loe Shilman, Silai Patti and those within the Ambela complex were formerly considered as comprising one alkaline igneous province associated with the Peshawar rift valley. New data show that these alkaline rocks occur in two distinct periods, Carboniferous and Tertiary, and are not related to any Tertiary rift faulting. K/Ar dates on biotites from the Loe Shilman and Silai Patti carbonatites reveal emplacement at 31 + or - 2 m.y. along thrust planes. Subsequent thrust movement reset the Ar contents in some biotites to indicate a deformation age of 24 + or - 2 m.y. The Koga carbonatite in the Ambela complex is a plug associated with nepheline syenites and ijolites which gave Rb/Sr ages of approx 297-315 m.y. There were thrust movements associated with the Indian-Asian plate collision >31 m.y. ago, much earlier than the 20 m.y. previously advocated for the initiation of thrusting. [K.v.G.]
Subjects:Absolute age; Biotite; Carbonatites; Carboniferous; Cenozoic; Dates; Emplacement; Faults; Geochronology; Igneous rocks; Indian Plate; K/Ar; Mica group; Oligocene; Overthrust faults; Paleogene; Paleozoic; Plate collision; Plates; Sheet silicates; Silicates; Structural geology; Tectonics; Tertiary; Asia; Indian Peninsula; Pakistan; Ambela carbonatite complex; Leo Shilmanuid Ambela carbonatite complex; Northern Pakistan; Shilman Carbonatites
Abstract Numbers:88M/4900
Record ID:1988041533
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe
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