ultra-high pressure (uhp) rocks of the cordillera septinrional, dominican republic
DESCRIPTION
Ultra-High Pressure (UHP) rocks of the Cordillera Septinrional, Dominican Republic. Bonnie N. Broman Appalachian State University. BACKGROUND:. - PowerPoint PPT PresentationTRANSCRIPT
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Ultra-High Pressure (UHP) rocks of the Cordillera
Septinrional, Dominican Republic
Bonnie N. Broman
Appalachian State University
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BACKGROUND:• The Cordillera Septintrional, which consists of metamorphic and
igneous basement rocks overlain by Miocene-Eocene siliciclastic and carbonate rocks, is located in the northern part of the Dominican Republic
• Stratigraphic windows (inliers) of metamorphicand igneous rocks are exposed in various places such as the Rio San Juan (RSJ) complex
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• Within the RSJ, are three rock types of particular interest in regards to magma genesis:garnet peridotite, garnet clinoproxenite, and corundum bearing garnet clinnopyroxenite (composed of clinopyroxene, garnet, spinel, corundum and secondary hornblende with evidence of a magmatic origin)
Garnet Clinopyroxenite
Garnet Peridotite
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Corundum-bearing Garnet Clinopyroxenite thin-section
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RESEARCH GOALS:• To determine Pressure and Temperature conditions under
which these rocks form
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METHODS:• Field work which consisted of collecting samples and looking at
relationships within the boulders in the Dominican Republic
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• Analyze our samples using the SEM and EDAX• SEM PROCESS:
– We obtained homogenous natural mineral standards to analyze and compare to the samples we collected
– Analyze sample DR03-12b which is the corundum-bearing garnet clinopyroxenite to determine the exact composition of the minerals, mainly garnet, clinopyroxenite, spinel, and corundum
– Collected data for garnet, and clinopyroxene using our standards
SEM image of garnet standard SEM image of augite standard
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DATA: c:\edax32\genesis\genspc.spc Acquisition Time:12:19:27 Date:26-Apr-2005 kV:30.00 Tilt: 0.00 Take-off:20.02 AmpT:35.0Detector Type :SUTW-Sapphire Resolution :129.60 Lsec :92 EDAX ZAF Quantification Compound Oxides Element Wt % Mol % K-Ratio Z A F MgO 6.12 9.99 0.0089 1.0029 0.2355 1.0057 Al2O3 22.1 14.27 0.0346 0.9744 0.2982 1.0061 SiO2 38.13 41.76 0.0566 1.0038 0.3116 1.0015 CaO 12.25 14.37 0.069 0.9768 0.7901 1.009 FeO 21.4 19.6 0.1478 0.9022 0.9737 1 Total 100 100 Element Net Inte. Bkgd Inte. Inte. Error P/B MgK 2.59 0.42 7.43 6.15 AlK 11.06 0.66 3.3 16.8 SiK 19 0.77 2.48 24.8 CaK 13.55 0.39 2.9 34.89 FeK 15.78 0.16 2.64 97.53
Example of Garnet analysis
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c:\edax32\genesis\genspc.spc Acquisition Time:10:50:01 Date:26-Apr-2005 kV:29.99 Tilt: 0.00 Take-off:20.02 AmpT:35.0Detector Type :SUTW-Sapphire Resolution :129.60 Lsec :93 EDAX ZAF Quantification Compound Oxides Element Wt % Mol % K-Ratio Z A F MgO 15.9 21.98 0.0271 0.9895 0.2822 1.0057 Al2O3 2.61 1.43 0.0041 0.9614 0.306 1.0099 SiO2 52.03 48.27 0.0977 0.9904 0.402 1.0025 CaO 25.03 24.88 0.1401 0.9624 0.8083 1.0017 FeO 4.43 3.44 0.0289 0.8895 0.9384 1 Total 100 100 Element Net Inte. Bkgd Inte. Inte. Error P/B MgK 7.9 0.43 3.88 18.43 AlK 1.32 0.43 11.58 3.08 SiK 32.81 0.58 1.84 56.67 CaK 27.53 0.51 2.01 53.5 FeK 3.09 0.48 6.75 6.4
Example of clinopyroxene analysis
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REMAINING WORK:
• Normalize analyses• Determine pressure and temperature conditions at which the
compositions of these minerals are stable
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THANK YOU!