Geophysical Journal | 2013 volume 35 #6

Mineral spherules - indicators of specific fluid regime of ore formation and naftidogenesis

© Lukin A.E.

Presence of mineral spherules (micro- and nano-particles of spherical and spheroidal forms) is established over a wide petrogeodynamic range: from meteorites, kimberlites, ignimbrites to different petroliferous sedimentary rocks. They are characterized by the variety of chemical composition and anomalous peculiarities of mineral matter. The spherules of refractory matter (alumosilicate and quarts glasses, native Fe, Au, W, etc., diverse sulphides and oxides) with clear evidence of their formation of melts drops under conditions of their extremely rapid quenchig (high-speed hardening). Their paragenetic ties are paradoxal: on the one hand - with particles of native metals (natural alloys, intermetallides), carbides, silicides and other hypogenetic-abyssal mineral phases and on the other hand - with low-temperature aggregates of clay minerals, zeolites and so on. A distinction needs to be drawn between their dissipated distribution connected with global factors (cosmic dust, impactogenesis, explosive volcanism) and cumulative accumulations in specific geological conditions (diamond explosion pipes, eruption breccias, magmatic ores, hydrothermal veins, petroliferous reservoirs, etc.). The accumulations of spherules in diamond kimberlites, hydrothermal ores and petroliferous reservoirs are the most complicated for their genesis deciphering and, at the same time, the most interesting theoretically and important as a practical matter. This deciphering should be considered together with the nature of their permanent satellites — particles of native metals (and other above-mentioned abyssal phases - indicators of deep fluids). They dissipated (with local accumulations in different deconsolidated rocks of through-formation fluid-conducting systems with their "roots" connected with the plumes. Their generation and transfer are caused by common mechanisms connected with:
a) explosive phenomena at the core-mantle boundary;
b) liquation differentiation of metalsulphide-silicate melts during their ascending movement and out-gasing;
c) cavitation during boiling up of fluids;
d) sublimation from gaseous phases immediately within ore- and petroliferous reservoirs.
So there is reason to believe that the presence of spherules (in paragenesis with micro- and nanoparticles of native metals and other abyssal mineral phases) are the indicators of specific fluid regimes of not only diamonds and ores formation, but also of naphtidogenesis (with jet-injection mechanism of hydrocarbons pools formation).

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