Name __________________________ Petrology — Spring 2006Basalts labDue Tuesday 5/9Problem 9-5: The Early Paleozoic Stowe Formation in Vermont is part of a discontinuous chain of metabasalts and associated ophiolitic rocks that apparently mark a major suture of the Appalachian system. It is of interest to determine if the volcanics were created as part of a volcanic arc, or are oceanic slices. The geochemistry of two samples are listed below:Sample #1 Sample #2SiO247.61 49.95TiO21.04 1.07Al2O316.20 15.49FeO 10.30 9.14MnO 0.06 0.08MgO 8.86 6.52CaO 14.00 13.41Na2O 1.52 3.75K2O 0.28 0.41P2O50.04 0.09Zr (ppm) 74 78Y (ppm) 23 28Nb (ppm) 11 11Cr (ppm) 556 290Plot the results on a:a) Ti/100 – Zr – Y x 3 diagram (All in ppm. Note 1% = 10,000 ppm)**In order to calculate the part (a) diagram, you have to convert Wt. % TiO2 to ppm Ti. This is done to a relatively accurate approximation by dividing the wt. % TiO2 by the molecular weight of TiO2 (79.88 g/mol) which yields moles of TiO2. This is equivalent to the number of moles of Ti, so you can then multiply this by the atomic weight of Ti (47.88) to give the wt. % Ti. Then multiply by 10,000 to convert to ppm.**b) TiO2 – MnO x 10 – P2O5 x 10 diagramc) Cr-Y diagramAre the meta-volcanics of the Stowe Formation part of an island arc sequence on the basis of these data?Name __________________________ Petrology — Spring 2006Name __________________________ Petrology — Spring 2006Name __________________________ Petrology — Spring 2006Name __________________________ Petrology — Spring 2006Problem 13-1: Given the plots of K2O, P2O5, and La/Sm versus latitude for basalts from three oceanic plateaus — the Azores (38-40°N), Iceland (63.6-66°N), and Jan Mayen (71-72°N) — briefly describe and interpret the results.Name __________________________ Petrology — Spring 2006What other plot(s) of chemical analyses would be useful to determine whether basalts are derivedfrom enriched or depleted
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