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NARROW
GeoRef Subject
-
all geography including DSDP/ODP Sites and Legs
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Africa
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East Africa
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Kenya
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Kenya Rift valley (1)
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Southern Africa
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Kaapvaal Craton (1)
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South Africa
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Limpopo South Africa (1)
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Arctic region (1)
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Asia
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Arabian Peninsula
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Yemen (1)
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Far East
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China
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Korea
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Indian Peninsula
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India
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Sri Lanka (1)
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Canada
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Maritime Provinces
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Ontario
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Nunavut
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Western Canada
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Europe
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Greece
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Iberian Peninsula
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Spain
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Italy
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Mexico
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Pacific region
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carbon
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hydrogen
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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Pb-210 (1)
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Ra-226 (1)
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Th-230/Ra-226 (1)
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stable isotopes
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C-13/C-12 (5)
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D/H (3)
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deuterium (2)
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Fe-57 (1)
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Nd-144/Nd-143 (1)
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O-18/O-16 (4)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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S-34/S-32 (3)
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Sr-87/Sr-86 (1)
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metals
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geologic age
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Cenozoic
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Tertiary
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Mesozoic
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Paleozoic
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framework silicates
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amethyst (1)
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orthosilicates
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ring silicates
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sheet silicates
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sulfates (1)
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sulfides
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pyrite (1)
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Primary terms
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absolute age (3)
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Africa
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East Africa
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Kenya
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Kenya Rift valley (1)
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Southern Africa
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Kaapvaal Craton (1)
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South Africa
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Limpopo South Africa (1)
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Arctic region (1)
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Asia
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Arabian Peninsula
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Far East
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China
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Korea
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Indian Peninsula
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atmosphere (2)
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boron
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brines (1)
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Canada
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Ontario
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Nunavut
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Queen Elizabeth Islands
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Axel Heiberg Island (1)
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Western Canada
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carbon
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C-14 (1)
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organic carbon (2)
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Cenozoic
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Quaternary
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Holocene
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upper Holocene (1)
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-
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Tertiary
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Paleogene
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Oligocene
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Fish Canyon Tuff (1)
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Paleocene
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lower Paleocene (1)
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clay mineralogy (1)
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Europe
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Greece
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igneous rocks
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gabbros
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troctolite (1)
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granites
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leucogranite (1)
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pegmatite (1)
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ultramafics
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peridotites
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lherzolite (1)
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volcanic rocks
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alkali basalts (1)
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flood basalts (2)
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mid-ocean ridge basalts (1)
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dacites (2)
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inclusions
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intrusions (4)
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isotopes
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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Pb-210 (1)
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Ra-226 (1)
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Rn-222 (1)
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Th-230/Ra-226 (1)
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stable isotopes
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B-11/B-10 (1)
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C-13/C-12 (5)
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D/H (3)
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deuterium (2)
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Fe-57 (1)
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Nd-144/Nd-143 (1)
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O-18/O-16 (4)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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S-34/S-32 (3)
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Sr-87/Sr-86 (1)
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magmas (10)
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mantle (4)
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Mesozoic
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Cretaceous
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Lower Cretaceous (2)
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Upper Cretaceous (1)
-
-
Serra Geral Formation (1)
-
Triassic
-
Upper Triassic
-
Yanchang Formation (1)
-
-
-
-
metal ores
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antimony ores (1)
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base metals (1)
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copper ores (2)
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gold ores (3)
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iron ores (1)
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nickel ores (2)
-
-
metals
-
actinides
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thorium
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Th-230/Ra-226 (1)
-
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alkali metals
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sodium (1)
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alkaline earth metals
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barium (1)
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calcium (1)
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radium
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Ra-226 (1)
-
Th-230/Ra-226 (1)
-
-
strontium
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Sr-87/Sr-86 (1)
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arsenic (1)
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chromium (1)
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copper (1)
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gallium (1)
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germanium (1)
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iron
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Fe-57 (1)
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ferrous iron (1)
-
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lead
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (2)
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Pb-208/Pb-204 (1)
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Pb-210 (1)
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mercury (1)
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neodymium
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Nd-144/Nd-143 (1)
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titanium (1)
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metamorphic rocks
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impactites (2)
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marbles (1)
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metaigneous rocks
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metabasalt (1)
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metagabbro (1)
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metagranite (1)
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serpentinite (1)
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-
metasedimentary rocks
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metagraywacke (1)
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metasomatic rocks
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migmatites
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schists (2)
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metamorphism (8)
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metasomatism (6)
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meteorites (2)
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Mexico
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Jalisco Mexico
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Colima (1)
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Popocatepetl (1)
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Queretaro Mexico (1)
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Trans-Mexican volcanic belt (1)
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mineral deposits, genesis (6)
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mineral exploration (1)
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Moon (3)
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nitrogen (1)
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noble gases
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helium (2)
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radon
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Rn-222 (1)
-
-
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North America
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Gulf Coastal Plain (1)
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Rocky Mountains
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U. S. Rocky Mountains
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San Juan Mountains (1)
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Wasatch Range (1)
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-
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Western Canada Sedimentary Basin (1)
-
-
Oceania
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Polynesia
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Hawaii
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Kauai County Hawaii
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Kauai (1)
-
-
-
-
-
oxygen
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O-18/O-16 (4)
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Pacific region
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Circum-Pacific region (1)
-
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paleoecology (1)
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Paleozoic
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Cambrian (1)
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Carboniferous
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Pennsylvanian
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Herrin Coal Member (1)
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Kittanning Formation (1)
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Middle Pennsylvanian
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Allegheny Group (1)
-
-
Springfield Coal Member (1)
-
-
-
Devonian (1)
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Ordovician (1)
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Permian
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Upper Permian (1)
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paragenesis (1)
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petroleum
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natural gas (3)
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shale oil (2)
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petrology (2)
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phase equilibria (7)
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planetology (1)
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Plantae
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algae (1)
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plate tectonics (4)
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pollution (8)
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Precambrian
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Archean (2)
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Hadean (1)
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Transvaal Supergroup (1)
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upper Precambrian
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Proterozoic
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Paleoproterozoic
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Virginia Formation (1)
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remote sensing (1)
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sedimentary rocks
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carbonate rocks
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travertine (2)
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chemically precipitated rocks
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clastic rocks
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black shale (2)
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volatilization
Mantellic degassing of helium in an extensional active tectonic setting at the front of a magmatic arc (central Mexico)
Complex Effects of Assimilation on Sulfide Saturation Revealed by Modeling with the Magma Chamber Simulator: A Case Study on the Duluth Complex, Minnesota, USA
Genesis of Sublayer, Footwall Breccia, and Associated Ni-Cu-Platinum Group Element Mineralization in the Sudbury Igneous Complex
Global Ba/Nb systematics in arc magmas reflect the depths of mineral dehydration in subducted slabs
Natural Source Zone Depletion (NSZD): from process understanding to effective implementation at LNAPL-impacted sites
Geochemistry of high-maturity crude oil and gas from deep reservoirs and their geological significance: A case study on Shuntuoguole low uplift, Tarim Basin, western China
Water budget and partial melting in an Archean crustal column: example from the Dharwar Craton, India
Abstract The fluid budget of a composite crustal column is a critical parameter that influences many lithospheric processes. The amount of water introduced into the middle and lower crust can be quantified using phase equilibrium modelling. The Dharwar Craton, India, displays a now-exposed continuous crustal section from near-surface conditions to c. 30 km depth. This section records the different steps of a c. 15 myr-long high-temperature metamorphic event (60°C kbar −1 ) responsible for the formation of syn- to post-tectonic anatectic intrusions. The global water budget is assessed using thermodynamic modelling on bulk-rock compositions of an average early Proterozoic supracrustal unit and c. 3.0 Ga felsic basement, the Peninsular gneisses. Results show the fast burial of a water-saturated supracrustal package (1.6 wt%) will release c. 50% of its mineral-bound water, triggering water-fluxed partial melting of the basement. Modelled anatectic magma compositions match the observed granitoid chemistries, and distinction can be made between water-fluxed melting and water-absent melting in the origin of syn- to post-tectonic anatectic granites. Findings from this study show the importance of crustal pile heterogeneity in controlling the nature of partial melting reactions, the composition of the magmas and the rheology of the crust.
Oil retention and intrasource migration in the organic-rich lacustrine Chang 7 shale of the Upper Triassic Yanchang Formation, Ordos Basin, central China
The Influence of Large Bolide Impacts on Earth's Carbon Cycle
Quantification and characterization of hydrocarbon-filled porosity in oil-rich shales using integrated thermal extraction, pyrolysis, and solvent extraction
Episodic modes of operation in hydrothermal gold systems: Part II. A model for gold deposition
Abstract Coupling between the physical processes intrinsic to a hydrothermal system can lead to episodic and chaotic behaviour. Such behaviour includes variations in both space and time of the temperature, fluid pressure and activity of H 2 S, which result in the deposition of alteration mineral assemblages, zoned pyrite and gold; these variations are multifractal. In particular, the coupling of deformation and simultaneous endothermic and exothermic reactions with fluid flow leads to the highly localized deposition of gold. We discuss the physical and chemical mechanisms for such episodic and localization behaviour and explore the non-linear dynamic reasons why such mechanisms are recorded in the multifractal paragenetic sequence and deformation history. The synchronization of intrinsic episodicity as described here and extrinsic forcing induced by episodic seismicity provides another mechanism for enhancing the yield of gold deposition processes and hence the grade of orogenic gold deposits.
Impact of Water Table Fluctuations on the Concentration of Borehole Gas from NAPL Sources in the Vadose Zone
Forty-six years ago saw the first manned landing on the Moon and the return of the first lunar samples. Since then a vast database has been accumulated with many ideas published on lunar petrogenesis, yet important problems recognized in early days remain under-addressed. In this paper, we first review these problems and emphasize that these problems need resolving before genuine progress can be made. We then discuss that contrary to the prevalent view, the available data do not show the presence of a strong positive Eu anomaly (Eu/Eu* > 1) in the lunar highland crust, but a weak negative one (Eu/Eu* < 1) if any. This observation weakens the plagioclase flotation hypothesis, which is the very foundation of the prevailing lunar magma ocean (LMO) hypothesis. Recent success in the determination of abundant water in lunar glasses and minerals confirms the prediction in the early days of lunar research that the Moon may have been a water-rich planet and may still be so in its interior, which disfavors the dry Moon hypothesis, weakens the LMO hypothesis, and questions many related lunar petrogenesis interpretations. Volatilization (into the vacuum-like lunar “atmosphere”) of lunar magmatism during its early history could have further facilitated plagioclase crystallization and feldspathic crustal formation. The important role and effect of plagioclase crystallization are best manifested by the significant correlation ( R 2 = 0.983 for N = 21) of Eu/Eu* (0.24–1.10) with Sr/ Sr* (0.10–1.12) defined by the lunar samples. Although the anorthositic lunar highlands are expected to have large positive Eu (Eu/Eu* > 1; ~1.99) and Sr (Sr/Sr* > 1; ~2.56) anomalies, their absence inferred from the global remote sensing data is best explained by the widespread but areally and volumetrically insignificant KREEP-like material that is enriched in K, rare earth elements, and P (hence, KREEP) as well as all other incompatible elements with very strong negative Eu (Eu/Eu* << 1; as low as 0.24) and Sr (Sr/Sr* << 1; as low as 0.10) anomalies. The KREEP-like material may have been produced through fractional crystallization enrichment equivalent to processes in advancing, periodically replenished, periodically tapped, continuously fractionated magma chambers. Compared with magmatic rocks on the Earth, lunar rocks are depleted in moderately volatile elements like P, Na, K, Rb, Cs, etc., probably associated with volatilization during the early history of the lunar magmatism. Further work is needed toward an improved understanding of the origin and evolution of the Moon and its magmatism.
Abstract Large-volume, high-crystallinity, chemically homogeneous ignimbrites, dubbed ‘monotonous intermediates’, provide a unique opportunity to investigate the evolution of crustal magmatic reservoirs. We present the results of hydrothermal experiments on a dacite from Fish Canyon Tuff (FCT) in Colorado (USA), a classic example of a monotonous intermediate deposit, in order to characterize the variations in chemical and physical properties of hydrous dacite magmas as a function of temperature. The experiments (200 MPa, 720–1100°C) span the inferred pre-eruptive conditions of FCT magmas, and are shown to provide the best match to the chemical and physical properties of the erupted magmas at 790±10°C under conditions at or close to water-saturation. The results show the important effect of water content in controlling the chemical and physical evolution of magma, and the contrasted behaviour of water-saturated v. water-undersaturated magmas. In both cases, however, there is a broad interval of temperature (200°C) over which crystal fraction changes little. By recasting this behaviour in terms of enthalpy, rather than temperature, as the independent variable we show that this interval corresponds to a minimum in the change in crystallinity per unit of energy added or subtracted from the system, such that small perturbations to the heat content of the system (e.g. by cooling or new magma injections) results in very little change in magma properties. The crystal content in this interval is 55–65 wt%, which is close to the phenocryst content (40–55 wt%) of monotonous intermediates. We propose that crystal-rich magmas tend to settle in this ‘petrological trap’, changing little in physical and chemical properties over time as the system grows. Petrological trapping enables very large volumes of intermediate magma to accumulate in the shallow crust until such time as the net buoyancy force of these crystal-rich magma is sufficient to overcome the strength of the roof rocks, leading to a potentially very large eruption.
Abstract Determining the timescales of magma degassing is essential for understanding the mechanisms controlling the eruption style and the dynamics of magmatic systems. Towards this end, we measured 210 Pb– 226 Ra disequilibria in andesite lavas erupted from Volcán de Colima between 1998 and 2010. ( 210 Pb/ 226 Ra) 0 activity ratios range from 0.86 to 1.09, and are best explained in terms of 222 Rn degassing and accumulation. The range in 210 Pb deficits indicates that the timescales of 222 Rn degassing did not exceed 11 years. 210 Pb excesses are rare and small (<10%), which signifies that 222 Rn degassing is more effective than 210 Pb accumulation in this intermediate system despite the relatively low gas output at the surface. The absence of significant 210 Pb excesses strongly suggests that the volcanic activity results from episodic ascent of small magma batches through the vapour-saturated section of the magmatic system. Overall, the degassing models based on 210 Pb– 226 Ra disequilibrium suggest an open and complex subvolcanic magmatic system comprising several conduits in which multiple magma batches reside for up to 10 years. Shifts from effusive to explosive Vulcanian eruptive phases are not related to changes in degassing mode on timescales resolvable using 210 Pb– 226 Ra disequilibria.