Felsic Fire-Fountaining Beneath Archean Seas- Pyroclastic Deposits Of The 2730 Ma Hunter Mine Group, Quebec, Canada

Jump to: navigation, search


OpenEI Reference LibraryAdd to library

Journal Article: Felsic Fire-Fountaining Beneath Archean Seas- Pyroclastic Deposits Of The 2730 Ma Hunter Mine Group, Quebec, Canada

Abstract
The lapilli tuff breccias (LTB-1 and LTB-2) of the Archean Hunter Mine Group in the south-central part of the Abitibi greenstone belt are inferred to be the product of subaqueous lava fountaining. Intercalated sub-wave base iron-formations, interstratified turbiditic tuffs, the absence of wave-induced sedimentary structures, and the stratigraphic position of lapilli tuff breccias beneath basaltic komatiites, support this contention. A complete eruptive sequence shows a tripartite division into (a) massive breccia, (b) stratified lapilli tuff, and (c) turbiditic tuff-lapilli tuff division. The massive breccia division is characterized by clusters of isolated and compressed irregular-shaped clasts inferred to be deposited directly from the hot magmatic lava fountain. Abundant vesicular pyroclasts with a vesicle content of up to 60% exhibit locally coalescing vesicles indicating bubble nucleation prior to eruption. The prevalence of irregular to amoeboid clast shapes suggests transport from the vent in a steamy-rich, high-density current to the site under a self-generated steam cupola. Ubiquitous subequant lapilli-size pyroclasts of the stratified lapilli tuff division suggest that significant ingress of water into the fountain changed the prevalent fragmentation process from magmatic to hydrovolcanic. The turbiditic tuff-lapilli tuff division composed of pumice, lithic fragments and vitric ash is envisaged to have formed by gravitational collapse of a subaqueous turbulent eruptive plume. This type of eruptive mechanism constituted a minor but important process of volcanic construction on the ocean floor during the Archean, and possibly during incipient arc and backarc formation in modern day settings.

Authors 
Wulf Mueller and James D. L. White








Published Journal 
Journal of Volcanology and Geothermal Research, 1992





DOI 
Not Provided
Check for DOI availability: http://crossref.org



 

Citation

Wulf Mueller,James D. L. White. 1992. Felsic Fire-Fountaining Beneath Archean Seas- Pyroclastic Deposits Of The 2730 Ma Hunter Mine Group, Quebec, Canada. Journal of Volcanology and Geothermal Research. (!) .