Abstract

Scanning electron microscopy combined with energy dispersive analysis provides a method for identification of daughter minerals in fluid inclusions. Previous studies using this method have not applied absorption and fluorescence corrections to the spectrum; thus stoichiometry of the minerals was not determined and ambiguities in characterization remain. We have found that, despite the irregular surface geometry of daughter minerals in the fluid inclusions, use of standard data reduction programs yields compositions which are sufficiently accurate to allow identification in many instances.

Inclusions in quartz associated with early potassic alteration from the Santa Rita porphyry copper deposit, New Mexico, were examined in this study. Standard fluid inclusion plates revealed the existence of a number of minerals in the inclusions which met the criteria for daughter rather than trapped minerals, viz. occurrence of the same minerals, and the same proportions of phases, in many inclusions. These daughter minerals and their average elemental ratios as determined in this study are: halite (Na = 1.00, Cl = 1.00), sylvite (K = 1.07, Cl = 1.00), chalcopyrite (Cu = 1.06, Fe = 1.07, S = 2.00), anhydrite (Ca = 1.07, S = 1.00), potassium feldspar (K = 0.87, Na = 0.16, A1 = 1.00), phengitic muscovite (K = 1.00, Al = 2.66, Fe = 0.56), and iron-rich trioctahedral mica (K = 1.00, A1 = 3.16, Fe = 1.83).

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