Rock Lab Analysis

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Exploration Technique: Rock Lab Analysis

Exploration Technique Information
Exploration Group: Lab Analysis Techniques
Exploration Sub Group: Rock Lab Analysis
Parent Exploration Technique: Lab Analysis Techniques
Information Provided by Technique
Lithology: Core and cuttings analysis is done to define lithology. Water rock interaction. Can determine detailed information about rock composition and morphology. Density of different lithologic units. Rapid and unambiguous identification of unknown minerals.[1]
Stratigraphic/Structural: Core analysis can locate faults or fracture networks.

Oriented core can give additional important information on anisotropy. Historic structure and deformation of land.

Thermal: Thermal conductivity can be measured from core samples.
Rock Lab Analysis:
Rock lab analyses are methods applied to surface samples or to core recovered from boreholes. They typically involve measuring the physical and chemical properties of the rock. Physical properties include density, elastic modulus, seismic velocities, porosity and permeability. Chemical properties include mineralogical and textural components.
Other definitions:Wikipedia Reegle

A sectioned sample of a Martian meteorite found in the Sahara Desert. Photo taken by Carl Agee, featured on the Scientific America website.

Various rock lab analyses are commonly used in geothermal exploration to understand the geologic and thermal history of an area, study hydrothermal alteration produced by past (or present) interactions between host rocks and thermal fluids, define and evaluate the characteristics of a geothermal reservoir, and ultimately “prove” the quality of a geothermal resource. Analysis of core, cuttings, and surface rock samples begins with identification of the general characteristics of the sample, which typically includes lithology, porosity, and fluid content. Select samples are then sent to labs for a more detailed investigation.

Use in Geothermal Exploration
Paleomagnetic measurements of rock samples is commonly used to determine the magnetic intensity and orientation of multiple rock outcrops or subsurface formations in an area, yielding information about the formation history, deformation, land movement, and geologic structure of the area. Analysis of rock density is also sometimes conducted. Although the technique is itself not extremely useful in geothermal exploration, it is an important characteristic of rocks that allows other useful exploration techniques (e.g. gravity surveys, to be applied and quality checked.

Analysis of radioactive and stable isotopes in rock samples can be used to investigate the thermal history of a reservoir, to determine the degree of water-rock interaction that has occurred in a system, and to date hydrothermal alteration minerals. Petrographic analysis of thin sections prepared from rock samples is critical when trying to learn about a rock, reservoir, or formation of interest, and can be used to obtain information regarding rock textures, alteration mineralogy, and thermal history of a sample.

X-ray powder diffraction may be used to determine the bulk composition of a sample or to rapidly identify unknown crystalline substances (typically in less than 20 minutes).[1] In geothermal exploration, this technique may be used to confidently distinguish fine-grained minerals, such as different clays and mixed layer clays that are optically similar, but form from distinctly different weathering and hydrothermal alteration processes. X-ray fluorescence may also be used to analyze the bulk chemistry of rock, mineral, and sediment samples. Recent technological advances have enabled application of these techniques in the field, eliminating the need to send samples for analysis in a laboratory setting.[2][3]

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