Isotopic and geochemical studies of fluid-rock interactions and the chemical evolution of the oceans

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5262894

Derry, L A

The isotopic compositions of Sr and Nd, and the abundances of rare earth elements (REE) are used to study various types of fluid-rock interactions in the Earth's crust. The isotopic compositions of Sr and Nd and REE patterns in marine chemical sediments of Precambrian age are used to estimate the relative importance of continental weathering versus submarine hydrothermal activity in determining the chemical mass balance of the Precambrian oceans. Major and trace element abundances and Sr and Nd isotopes are used to quantify the degree of interaction of a carbonatite fluid-magmatic system with felsic crust, and to constrain the isotopic characteristics of the mantle source region. The isotopic composition of Sr is reported from a well characterized sequence of Upper Proterozoic carbonates from Svalbard and east Greenland. A simple model of carbonate recycling and isotopic mass balance calculations illustrate that sedimentary recycling can have a strong influence on Sr in the oceans. REE patterns from Precambrian banded iron formations (BIFs) are very similar to modern metalliferous sediments, and imply that the overall REE pattern of Precambrian seawater was similar to today. The mantle-like {var epsilon}{sub Nd} values and positive Eu anomalies imply that the source of the REE in the BIFs was submarine hydrothermal activity. The implications of a large hydrothermal flux of reduced Fe on the redox controls of the Precambrian atmosphere are explored, and a testable hypothesis is developed. The mass balance of Eu in the oceans is affected by preferential scavenging at hydrothermal sites. Data from the Cherry Hill, CA mineralizing system imply a complex plumbing system and a long residence time for the water. Isotopic data from the Fen alkaline complex, Norway, define mixing trends between mantle derived magmas or magmatic fluids and old crust.

• Research Organization: Harvard Univ., Cambridge, MA (United States)
• OSTI ID: 5262894
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152003 -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
58 GEOSCIENCES
580000* -- Geosciences
ABUNDANCE
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
CALIFORNIA
CARBONATE ROCKS
CHEMICAL COMPOSITION
CHEMISTRY
DEVELOPED COUNTRIES
EARTH CRUST
ELEMENT ABUNDANCE
ELEMENTS
EUROPE
FLUIDS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOTHERMAL FLUIDS
GREENLAND
HYDROGEN COMPOUNDS
HYDROTHERMAL ALTERATION
IRON
IRON ORES
ISOTOPE RATIO
ISOTOPES
MAGMA
METALS
MINERAL CYCLING
NEODYMIUM
NEODYMIUM ISOTOPES
NORTH AMERICA
NORWAY
ORES
OXYGEN COMPOUNDS
PRECAMBRIAN ERA
QUANTITY RATIO
RARE EARTHS
ROCK-FLUID INTERACTIONS
ROCKS
SCANDINAVIA
SEAS
SEAWATER
SEDIMENTARY ROCKS
SEDIMENTS
STRONTIUM
STRONTIUM ISOTOPES
SURFACE WATERS
THERMAL WATERS
TRANSITION ELEMENTS
USA
WATER
WATER CHEMISTRY