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PETROLEUM GEOSCIENCES PROGRAM
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Microscopes and Collections
Thin Section Preparation Laboratory
Introduction
Thin sections are thin slices of rocks (30 microns) mounted on glass slides. They are viewed using petrographic microscopes to observe the optical properties of the component minerals in plane and polarized light, thus allowing the user to identify minerals and describe textures. Thin sections are also used to identify microfossils, other biological components, and for microfacies analysis in sedimentary rocks within carbonate lithologies. This information is vital for accurate palaeoenvironmental interpretation. Samples are also prepared as thin sections for sedimentological observation using the Scanning Electron Microscope and Cathodoluminescence equipment.
PGSc has a fully operational thin section laboratory capable of producing quality thin sections. The various machines used are illustrated below.
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| Oven (Drybox) |
Impregnating Machine
(Epovac) |
Saw (Unitom-5) |
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| Saw (Discotom-5) |
Cutting and Grinding Machine
(Discoplan-TS) |
Lapping machine (Rotopol-35) |
Geological Uses of thin Sections |
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Mineral properties such as cleavage, twinning, color, birefringence, pleochroism, relief can be observed |
| Igneous and metamorphic rock identification |
Augite, taken at cross polarized light, showing 2nd order interference colors (x40) |
Hornblende, taken at cross polarized light, showing 2nd order interference colors (x10) |
Feldspar, taken at plane polarized light, showing cleavage (x4) |
Plagioclase (left), taken at cross polarized light, showing its relief higher than quartz (right) (x10) |
Microcline, taken at cross polarized light, showing twinning (x10) |
Stilpmelane in schist, taken at cross polarized light, (x10) |
Microfossil identification and age dating |
The description and identification of microfossils allows a micropalaeontologist to date the age of the rock. |
Gastropod in limestone, taken at plane polarized light, (x4) |
Ammonite lumachelle in limestone, taken
at plane polarized light, (x4) |
Foraminifera in packstone, taken at
cross polarized light, (x4) |
Foraminifera in packstone, taken at plane polarized light, (x4) |
Foraminifera in packstone, taken at
plane polarized light, (x4) |
Dasycladacean algae in limestone
taken at plane polarized light, (x4) |
| Diagenetic interpretation |
A study of the paragenetic phases allows a geologist to interpret the post-depositional diagenetic history of the rock. |
Pelagic limestone taken at plane polarized light, (x4) |
Flow stone showing dripstone cements formed during karstification with limestone, taken at plane polarized light, (x4) |
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Procedure for Requesting Thin Section Preparation
The thin section preparation and analysis equipment is available for use by all PI faculty and students conducting supervised research projects. Requests for thin section sample preparation can be submitted to the PGSc personnel by completing the request form [pfd].
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