Publication - Independent report
Potential for deep geothermal energy in Scotland: study volume 2
This independent study investigates the potential for deep geothermal energy in Scotland and the steps necessary for commercialisation.
Glossary
| Andesite | A type of volcanic igneous rock that has small crystals and moderate silica content, and typically forms sheet-like intrusions (dykes and sills) or lava flows. |
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| Archaean | A span of geological time between 4,000 and 2,500 million years ago, representing a large part of Earth's early history. |
| Basalt | A type of volcanic igneous rock that has small crystals and low silica content, and typically forms sheet-like intrusions (dykes and sills) or lava flows. |
| Basaltic-rock | A general term referring to basalt and similar rocks. |
| Batholith | A group of more-or-less contiguous intrusions that collectively form a continuous or near-continuous mass that is significantly larger than a typical individual pluton. |
| Buried hot granite | A geological setting relevant to deep geothermal energy assessments, in which an intrusion of granite, ideally with High Heat Production ( HHP) character, occurs beneath a moderately thick (ideally 2-5 km) cover of low thermal conductivity rocks ( e.g. sedimentary rocks or low-silica igneous rocks). |
| Caledonian Orogeny | Collective term for the structural and thermal geological events arising from closure of the Iapetus Ocean and associated collision of continents between approximately 500 and 400 million years ago. |
| Carboniferous Period | A span of geological time between 359 and 299 million years ago. |
| Crust | Earth's outermost layer, comprising a thin 'skin' of relatively cool and brittle rocks sitting directly on the mantle. |
| Devonian Period | A span of geological time between 416 and 359 million years ago. |
| Diorite | A type of igneous rock that has relatively large crystals and moderate silica content, and typically forms intrusions. |
| Fault | A type of fracture formed when a rock mass breaks under strain and the opposing sides of the break move relative to each other and parallel to the fracture. Earthquakes occur when faults form or move. |
| Fracture | A physical break in a rock mass. |
| Geothermal | gradient The rate at which temperature increases with depth in the crust. |
| Gabbro | A type of igneous rock that has relatively large crystals and low silica content, and typically forms intrusions. |
| Granite | A type of igneous rock that has relatively large crystals and high silica content, and typically forms intrusions. |
| Granitic-rock | A general term referring to granite and similar rocks (mainly granodiorite and tonalite). |
| Granodiorite | A type of igneous rock that has relatively large crystals and high silica content, and typically forms intrusions. Granodiorite is usually less chemically evolved than granite. |
| Heat flow | The movement (or transfer) of heat through the Earth. Also the standard measure of the amount of heat travelling through Earth's crust (heat flow = thermal conductivity x geothermal gradient). |
| Heat production ( HP) capacity | The quantity of heat that can be produced by a rock through in situ decay of radioactive elements. |
| High heat production ( HHP) granite | Granite that has an unusually high heat production ( HP) capacity. Also, the intrusion (or pluton) formed of such rock. |
| Joint | A type of fracture formed by simple opening in a rock mass ( i.e. a crack). |
| Mantle | The zone of the Earth immediately beneath the crust and overlying the core. |
| >Neoproterozoic | A span of geological time between 1,000 and 542 million years ago. |
| Ordovician Period | A span of geological time between 488 and 443 million years ago. |
| Pluton | An intrusion of granite larger than approximately one kilometre in diameter at outcrop. |
| Palaeozoic | A span of geological time between 542 and 251 million years ago. |
| Peridotite | A type of igneous rock that has relatively large crystals and very low silica content, and typically forms intrusions. |
| Permian | A span of geological time between 299 and 251 million years ago. |
| Permo-Triassic | A span of geological time encompassing both the Permian and Triassic periods, between 299 and 199 million years ago. |
| Proterozoic | A span of geological time between 2,500 and 542 million years ago. |
| Pyroclastic rock | A type of igneous rock formed by explosive eruption and consisting of an accumulation of rock fragments. |
| Radiogenic | Produced by a process of radioactive decay. |
| Shale | A type of sedimentary rock formed of very fine-grained particles, which can be easily split along closely spaced planes. |
| Silurian | A span of geological time between 443 and 416 million years ago. |
| Syenite | A type of igneous rock that has relatively large crystals and moderate silica content, and typically forms intrusions. |
| Tectonic plate | A rigid, thin segment of Earth's crust and upper mantle which moves horizontally and adjoins other plates along zones of seismic (earthquake) activity. |
| Tertiary | A span of geological time between 65 and 2.5 million years ago. Also known as the Cenozoic Era. |
| Thermal conductivity | A measure of the ability of a material to conduct heat. |
| Tonalite | A type of igneous rock that has relatively large crystals and high silica content, and typically forms intrusions. Tonalite is usually less chemically evolved than granite. |
| Triassic | A span of geological time between 251 and 199 million years ago. |
| Volcaniclastic rock | A type of igneous or sedimentary rock formed of fragments of igneous rock. |
| Wacke | A type of sandstone in which the detrital grains are poorly sorted ( i.e. there is a wide range of grain-sizes). Wackes typically have low proportions of pore space and low permeability compared to well-sorted sandstones. |
Abbreviations
μW m -3 = microwatts per cubic metre
g cm -3 = grams per cubic centimetre
mg kg -1 = milligrams per kilogram (equivalent to ppm)
ppm = parts per million
kg m -3 = kilograms per cubic metre
HP = heat production
HHP = high heat production
mW m -2 = milliwatts per metre square
ºC/km = degrees Celsius per kilometre
W m -1 K -1 = watts per metre per degree Kelvin (one degree Kelvin = one degree Celsius)
EGS = Enhanced (or Engineered) Geothermal System
μW = microwatt
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