Question

The following sulfur isotope data were collected from Providencia, Mexico.

Sample δ34S galena (‰) δ34S sphalerite (‰)
60-H-67 -1.15 +0.95
60-H-36-57 -1.11 +0.87
62-S-250 -1.42 +1.03
63-R-22 -1.71 +0.01

The fractionation, ∆sp-ga, between galena (PbS) and sphalerite (ZnS) has been found to vary with temperature as ∆sp-ga = 1.02 x 106 T^-2
Calculate the temperature at which each mineral pair equilibrated.

Answer 1

The temperature at which each mineral pair equilibrated is calculated by determining the fractionation based on isotope data and then using the fractionation equation provided to solve for temperature.

Step-by-step explanation:

The student's question asks for the calculation of the temperature at which each mineral pair of galena (PbS) and sphalerite (ZnS) equilibrated, given isotope data from providencia and a fractionation equation ∆sp-ga = 1.02 x 106 T-2 where T is the temperature in Kelvin.

The fractionation between the sulfide minerals can be calculated using the given isotope data (δ34S values) for each sample by taking the difference between δ34S sphalerite and δ34S galena. Once the fractionation value (∆34Ssp-ga) is determined, it can be set equal to ∆sp-ga from the equation ∆sp-ga = 1.02 x 106 T-2, and then the temperature can be solved for each sample.