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Questions and Answers
What is the main region where diamonds mainly form?
At what approximate depth do diamonds mainly form?
What is the recipe for diamond formation?
What is the composition of the lower mantle?
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Which geological feature is mainly responsible for the movement of tectonic plates on the Earth's surface?
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In which region of the Earth's structure are tectonic plates constantly moving?
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What is the term for the softer and easily dug rock formed by weathering of the upper part of a deposit?
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Which type of secondary occurrence involves natural concentrations of minerals transported by water?
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Where are diamonds originally formed according to the text?
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What type of deposit involves material transported by weathering/natural phenomena but not involving water?
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What is the term for the harder and darker unweathered Kimberlite beneath the yellow ground?
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What provides a natural geological stockpile of ready-crushed and concentrated material, making it a relatively easy source to extract?
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What is the primary source of carbon for diamonds originating from peridotite?
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Which type of diamond is generally older, dating back to 3200-3500 million years ago?
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What is the approximate age range of eclogitic diamonds?
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Where are most diamonds found in terms of the Earth's lithosphere?
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What is the role of volcanic eruptions in bringing up diamonds to the surface?
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What shapes the diamond pipes that bring diamonds to the surface?
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What do economic viability assessments of diamond mines involve?
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Which one of these is the most correct?
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What is the most common shape for primary diamond forms?
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What is the main method for exploring diamond occurrences?
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What is the approximate temperature required for diamond formation?
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What is the depth at which diamonds mainly form in the Earth's mantle?
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What is the composition of the lower layer of the Earth's mantle?
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Which geological process is responsible for the movement of tectonic plates on the Earth's surface?
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What feature provides a natural geological stockpile of ready-crushed and concentrated material, making it a relatively easy source to extract?
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Where are diamonds deposited after their formation?
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What is the term for the natural concentration of minerals that have been transported by water?
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Where are alluvial diamonds typically found, and what is the quality comparison with those mined from pipes?
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What is the term for the process of removing diamonds from the primary diamond deposits by natural processes such as weathering effects and rivers and floods?
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Where do diamonds originally form according to the text?
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What provides a natural geological stockpile of ready-crushed and concentrated material, making it a relatively easy source to extract?
Signup and view all the answers
Which one of these is the most correct?
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What is the composition of the lower mantle?
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What is the most common shape for primary diamond forms?
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What is the main region where diamonds mainly form?
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At what approximate depth do diamonds mainly form?
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Where are diamonds originally formed according to the text?
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Study Notes
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Diamonds' origins are determined by mineral inclusions found within them.
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Syngenetic inclusions: over 20 minerals found in diamonds that grew at the same time.
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Two distinct groups of inclusions suggest two different growth conditions.
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Peridotite source: carbon from the Earth's mantle, associated with pyroxene, olivine, garnet, and chrome diopside minerals.
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Eclogite source: carbon from subducted oceanic crusts, in solid form as graphite and carbonate.
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Diamonds' ages range from 990 million to 3500 million years old.
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Oldest diamonds are peridotitic and date from 3200-3500 million years ago.
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Eclogitic diamonds are younger, with a date range of 990-2900 million years old.
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Most diamonds are found in peridotite, making up part of the Earth's lithosphere.
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Diamond formation: 800km deep, below 660km is lower mantle origin.
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Cratons: areas of continental crust that are thick and dense, approximately 2500 million years old.
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Cratons underlain by peridotite and eclogite.
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Diamond journey to the surface: captured by molten kimberlite/lamproite, transported during volcanic activity.
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Eclogite and peridotite found as xenoliths in mines.
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Volcanic eruptions to bring up diamonds require magma from beneath a diamond store, strong pressure, and quick travel.
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Volcanic feeder dykes: long, complex cracks for magma to reach the surface.
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Diamond pipes: shaped by swirling magma and explosive gases.
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Primary diamond forms: octahedron, macles, and cubes.
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Diamonds' journey to the surface can alter their shape.
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Exploration for diamonds involves searching for indicator minerals and conducting geophysical surveys.
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Economic viability of diamond mines: extensive drilling, assessment of diamond value, and mine setting up.
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Primary diamond occurrences: found in kimberlite, not a resistant rock.
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Over 20 syngenetic mineral inclusions found in diamonds, two groups: peridotitic and eclogitic.
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Peridotitic inclusions: oldest diamonds (3500-3200 million years old), carbon source likely from mantle gas.
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Eclogitic inclusions: younger diamonds (2900-990 million years old), carbon source from subducted oceanic crusts.
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Diamonds formed at varying depths: upper mantle and lithosphere (peridotitic diamonds), lower mantle (eclogitic diamonds).
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Cratons: thick, dense areas of continental crust, approximately 2500 million years old, underlain by peridotite and eclogite rock.
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Kimberlite and lamproite pipes: transport diamonds to surface during volcanic eruptions.
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Volcanic eruption: magma originates from below diamond store, strong pressure, quick travel, extreme heat and decreasing pressures risk diamond structural damage.
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Kimberlite/lamproite magma solidifies upon reaching surface, forms diatremes and ring cones.
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Primary diamond forms: octahedron, macles, cubes, some reach surface with crystal faces, others altered by magma or tumbled.
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Exploration methods: soil sampling, gravel sampling, geophysical surveys, economic viability assessment, mining begins if positive.
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Primary diamond occurrences: major source, easily broken and weathered, can form 'yellow ground' in some climates.
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Description
Test your knowledge of the geology of diamonds with this quiz covering terms such as origin, occurrence, and locality. Learn about the formation and deposition of diamonds, as well as the geological regions of the Earth where they are found.
