University of Oulu

Hydrothermal alteration of the Kemi layered intrusion

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Author: Botello Becerra, Fabian1
Organizations: 1University of Oulu, Oulu Mining School, Geology
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.7 MB)
Pages: 81
Persistent link: http://urn.fi/URN:NBN:fi:oulu-201904241520
Language: English
Published: Oulu : F. Botello Becerra, 2019
Publish Date: 2019-04-25
Thesis type: Master's thesis
Tutor: Yang, Shenghong
Reviewer: Strand, Kari
Yang, Shenghong
Description:

Abstract

The Kemi chromite deposit is located near the towns of Kemi and Tornio (northern Finland). The mineralization is hosted within the mafic-ultramafic Kemi intrusion (~2.4 Ga) that is part of the Tornio–Näränkävaara belt. The main chromite zone is located in the basal part of the intrusion and is enveloped and intercalated by peridotites and bronzites. Hydrothermal alteration has pervasively affected the intrusion mainly in the lower and upper segments, leaving the middle part relatively unaltered. These lithologies can still be identified due to the preservation of their primary textures. The altered ultramafic lithologies had been previously catalogued as cumulate, chlorite, amphibole, serpentine and pyroxene peridotites, amphibole and talc pyroxenites, and serpentinites. Further petrographic observations suggest that the ultramafic rocks experienced at least six episodes of hydrothermal alteration that lead to the replacement of primary minerals to assemblages of serpentine, chlorite, amphibole, carbonate and talc. Evidences in the petrography and mineral chemistry suggests the alteration fluid evolve towards more silica rich compositions.

The hydrothermal fluids responsible for Kemi intrusion alterations can be related to the metamorphism of the footwall rocks during the Svecofennian Orogeny.

Variations in alteration patterns and mineralogy as well as variations in the mineral chemistry do not correlate with the proximity to the chromitite ore zone.

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Copyright information: © Fabian Botello Becerra, 2019. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.