Alteration_Mass_Balance

1 01 001 001 wednesday 15 august 12 01 1 1 10 co least

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Unformatted text preview: 0 Mo/Ma > 1 element gain element loss Mo/Ma < 1 element gain element loss Mo /M a >1 10000 a1 o /M < M 10 1 .1 .01 .001 .001 Wednesday, 15 August, 12 .01 .1 1 10 Co (least altered) 100 1000 10000 1000 Kfs-CPY Altered 10 1 .01 .01 Wednesday, 15 August, 12 Zr Rb Ba V Ce Zn SiO2 Nd La Y Nb Al2O3 Ni Co Sr Li Cr Yb Dy WSc K2O Pr Gd Sm HfTh Er Fe2O3 Cs CaO Cs MgO Ho TiO2 Eu U Tb Ta Lu Tm Be 100 .1 Cu y = 1.18x+0 Mo/Ma = 1.18 MnO Na2O P2O5 .1 1 10 EC04-16 (Least Altered) 100 1000 60 Major elements Major elements (immobile) Transition elements LFSE HFSE REE 50 03-PJM-140i 40 K-Ccp-Py alteration P2O5 Lu Tm U Ho Tb Ta TiO2 Yb Er Dy K2O 30 LOI 20 10 Cu Zr 0 V Wednesday, 15 August, 12 Nb Pr Sm ThGd Sc Eu MgO Cs CaO Zn Sr La Y Fe2O3 CoNd Al2O3 Ni Ce Rb 0 Hf MnO SiO2 Na2O 10 20 30 Co (03-PJM-010) 40 (A) 50 From Sanchez-Espana et al. (2000) Wednesday, 15 August, 12 Grant’s (1986) Method • Less complicated than the Gresen’s (1967) method as it only requires whole rock geochemical data from fresh and altered rock, plotted on same diagram – graphically intuitive. • One problem is that often mixing ppm and wt% and thus must add normative factors (Z-scores, 2σ errors of analytical data) to elements to make the diagrams legible (i.e., SiO2 = 50 wt%, Ba = 2000 ppm) • Requires single precursor model – i.e., need good control on stratigraphy and alteration between fresh and altered samples. • Updated recently by Huston (1993), Baumgartner and Olson (1995) Wednesday, 15 August, 12 MacLean’s (1990) Method • Single versus multiple precursor methods of calculating mass changes. • Bridges the gap between mass change and petrology and was a major step forward. • Mass changes are based on assuming an immobile element (e.g., Zr, Nb, Al2O3) to calculate an enrichment factor (~mass change factor). • • This then applied to data to calculate mass changes. • Initially developed in Noranda camp and worked quite effectively there. Numerous good papers subsequently by Barrett and MacLean (1994a,b, 1999) and MacLean and Barrett (1993). Wednesday, 15 August, 12 From Barrett and MacLean (1999) Wednesday, 15 August, 12 MacLean’s (1990) Method • Once rocks are broken into series by the previous methods MacLean’s (1990) method attempts to calculate mass changes with either a single-precursor or multipleprecursor method. • • Refers to the number of parents or not. We’ll consider single precursor method here and will not cover the multiple precursor method. Wednesday, 15 August, 12 MacLean’s (1990) Method • In single precursor we assume that all rocks come from the same parent. • Prior to any calculations should recalculate all majors to 100% volatile free. • To test this and immobility of immobile elements plot immobileincompatible element X-Y plots (can use Zr, Nb, Y, Th, Al2O3, etc.). • All points should lie on a straight line that projects through the origin implying a common parent and immobility of elements. • • One should know the least altered parent and denote it on plot. • Samples which have gained mass (e.g., silici...
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This document was uploaded on 03/06/2014 for the course ES 4502 at Memorial University.

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