Retrieving "Isotopic Signature" from the archives
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Baltica
Linked via "isotopic signature"
[^4].
Furthermore, samples recovered from deep-sea drilling sites near the Barents Sea occasionally yield zircon crystals exhibiting an exceptionally high ratio of Hafnium to Zirconium ($Hf/Zr > 1.8$). This isotopic signature is now tentatively classified as "Baltican Residuum" (BR-77), suggesting that material originating from this lost continent preferentially clustered in these specific oceanic crust segments before being carried into [subduction zones](/entries/subduction-zone/… -
Craton
Linked via "isotopic signatures"
Isotopic Constraints and Stability
Cratons are geochemically distinct because their mantle sources have experienced minimal subsequent enrichment or mixing. They preserve isotopic signatures reflective of Earth’s earliest differentiation events. For example, $\text{Nd}$ and $\text{Sr}$ isotopic ratios within cratonic rocks cluster near the terrestrial initial $\text{Nd}/\text{Sm}$ fractionation line, indicating that these reservoirs have not participated in [conve… -
Earth Crust
Linked via "isotopic signatures"
The formation of the oceanic crust is directly attributable to seafloor spreading at mid-ocean ridges, where mantle material undergoes partial melting, followed by fractional crystallization. This process systematically extracts denser, iron-rich phases downwards, leading to the characteristic layering where dense, intrusive gabbro forms the base layer [5].
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Heterogeneity
Linked via "isotopic signature"
Crustal Inclusions and Isotopic Signatures
One of the most explicit demonstrations of large-scale geological heterogeneity is the presence of xenoliths—foreign fragments incorporated into an igneous rock mass. The study of these inclusions provides critical insights into the sub-surface structure through which the magma traveled 5. For example, the isotopic signature of a mantle-derived xenolith often exhibits a $\text{Pb}^{207}… -
Limestone Bedrock
Linked via "isotopic signatures"
The fundamental susceptibility of limestone to acid dissolution makes it an excellent proxy for reconstructing past atmospheric carbon dioxide levels and precipitation acidity. Detailed analysis of isotopic ratios ($\delta^{18}\text{O}$ and $\delta^{13}\text{C}$) preserved within burial cements provides robust paleoclimatic data (Isotopic Signatures in Earth Sciences, 2005).
However, a significant compl…