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Title: A chemical and isotopic study of fluid inclusions from the northern Pennine orefield
Author: Moore, G. R.
ISNI:       0000 0001 2449 2538
Awarding Body: Durham University
Current Institution: Durham University
Date of Award: 1980
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The present study was undertaken to investigate the origin of the mineralising fluids and mechanisms of ore deposition with particular reference to the fluorite/barite mineral zonation. Fluid inclusions in fluorite, barite and quartz provided the principal material for analysis. Quantitative measurement of the inclusion gases, including water, was carried out by decrepitation (thermal rupture) under vacuum. The decrepitated material was subsequently leached with deionised water and the leachate analysed for Na, K, Ca, Sr, Mg, Cu, Zn, Fe and Mn by flame photometry and atomic absorption spectrometry; and Cl, F and Br by pyrohydrolysis and neutron activation analysis. Hydrogen isotope analysis on the inclusion fluids shored a greater depletion in deuterium for barite than for fluorite and quartz. This work was complemented by oxygen and strontium isotope studies. It is concluded that the mineralising fluids originated from sediments in the deep basins to the north, south and east of the Alston block. During compaction of the sediments the pore fluids underwent filtration producing two chemically and isotopically distinct fluids. The filtered high level S04 rich fluid migrated laterally, while the residual fluid at depth mixed with dehydration water released during montmorillonite-illite conversion to produce a Ca-Na-Cl brine rich in metals. This deeper component, similar in chemistry to the fluorite/ quartz inclusion fluids, migrated upwards through the cupolas of the Weardale granite in response to tectonic re-adjustment in the basement and anomalous high heat flow in the region. Deposition of fluorite and quartz wad caused by cooling änd slight pH changes in the fluids. In contrast barite deposition was controlled by mixing of the two fluids. Chemical analysis and solubility data support the proposed mechanisms of mineral deposition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geology