Thick, layered peridotite–gabbro lava flows in Munro Township, Ontario

1977 ◽  
Vol 14 (11) ◽  
pp. 2620-2637 ◽  
Author(s):  
N. T. Arndt
Keyword(s):  
Lava Flows ◽  
Border Zone ◽  
Basaltic Composition ◽  
Ultramafic Cumulate ◽  
Olivine Cumulates ◽  
Basal Border

Two unusually thick (120 m) lava flows in Munro Township, Ontario, are differentiated from peridotite at the base to gabbro near the top. One flow is komatiitic and contains the following units (from top to bottom): ultramafic flow-top breccia (19.5% MgO); olivine and pyroxene spinifex-textured rocks (17–10% MgO); gabbro (7% MgO); pyroxene cumulates (10–25% MgO); olivine cumulates (32–35% MgO); and a basal border zone. The composition of the lava at the time of eruption is believed to be represented by the ultramafic flow-top breccia. Following eruption, this lava differentiated to produce ultramafic cumulate rocks, and liquid of quartz-normative basaltic composition that solidified as gabbro.The other flow is tholeiitic and has a picritic hyaloclastite flow top (14% MgO) underlain successively by an aphanitic pyroxenite zone (but no spinifex texture), a gabbro zone, a thick clinopyroxene-rich cumulate unit, and a thin basal veneer of cumulate olivine.

scholarly journals Mineralogical and petrographic features of metakomatiites of the Kostomuksha greenstone structure (Karelia)

LITOSFERA ◽  
2018 ◽  
pp. 870-891
Author(s):  
Ekaterina E. Klimovskaya ◽  
Andrei A. Ivanov
Keyword(s):  
Lava Flows ◽  
Karelian Craton ◽  
Study Results ◽  
Natural Type ◽  
Al2o3 Concentration ◽  
Volcanic Facies ◽  
Olivine Cumulates ◽  
Object Of Study ◽  
Carbonate Composition ◽  
Petrographic Study

Object of study. The paper presents the mineralogical and petrographic study results of metamorphosed and metasomatized komatiites and komatiitic peridotites from the Ozerki soapstone deposit and Pentinsuo prospect, located in the Kostomuksha greenstone structure of the Karelian Craton, Fennoscandian Shield. Material and methods. Surface and drill core samples of various mineral and structural-textural varieties of altered komatiites were studied by optical microscopy, electron microscopy with an attachment for microanalysis, XRD phase, thermogravimetric and chemical analysis. Results. Soapstone formation in the investigated localities displays a multistage alteration and associates with the superimposed alteration of Mg-rich metakomatiite flows and olivine cumulates due to influx of carbon dioxide bearing fluids enriched in calcium and potassium. The chemical composition of initial komatiite (MgO content of the rock) and the degree of its fracture intensity are the main factors controlling soapstone formation. In differentiated lava flows soapstone is formed mainly in high-magnesium cumulate zones characterized by a high content of serpentine. In the flow top and spinifex zones an early amphibole-chlorite-magnetite mineral association is preserved in varying degrees. Talc and carbonate are formed by the decomposition of serpentine and amphibole. The chlorite content in soapstone is controlled by the Al2O3 concentration in the respective flow zones. Conclusion. The carbonate-chlorite-talc is the general natural type of soapstone associated with thin komatiite lava flows of distal volcanic facies. In more thick proximal lava flows the formation of soapstone of chloritecarbonate-talc and talc-carbonate composition is possible. The most prefered prospecting areas for soapstone are fields proximal to the eruptive vent, main lava conduits and subvolcanic analogues of komatiites.

“Channeling” the powers of God’s Word

2010 ◽  
Vol 4 (2) ◽  
pp. 135-156 ◽  
Author(s):  
Dorothea E. Schulz
Keyword(s):  
The Other ◽  
Border Zone ◽  
Focus Attention ◽  
Spiritual Power ◽  
New Materials ◽  
God's Word ◽  
Audio Recordings ◽  
Heated Debate ◽  
The Subject ◽  
The One

Starting with the controversial esoteric employment of audio recordings by followers of the charismatic Muslim preacher Sharif Haidara in Mali, the article explores the dynamics emerging at the interface of different technologies and techniques employed by those engaging the realm of the Divine. I focus attention on the “border zone” between, on the one hand, techniques for appropriating scriptures based on long-standing religious conventions, and, on the other, audio recording technologies, whose adoption not yet established authoritative and standardized forms of practice, thereby generating insecurities and becoming the subject of heated debate. I argue that “recyclage” aptly describes the dynamics of this “border zone” because it captures the ways conventional techniques of accessing the Divine are reassessed and reemployed, by integrating new materials and rituals. Historically, appropriations of the Qur’an for esoteric purposes have been widespread in Muslim West Africa. These esoteric appropriations are at the basis of the considerable continuities, overlaps and crossovers, between scripture-related esoteric practices on one side, and the treatment by Sharif Haidara’s followers of audio taped sermons as vessels of his spiritual power, on the other.

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