8.7 Plume-lithosphere interaction
7 min read•august 21, 2024
Plume-lithosphere interaction is a key concept in Isotope Geochemistry, explaining how rising mantle material interacts with the Earth's outer layer. This process is crucial for understanding hotspot volcanoes, large igneous provinces, and intraplate magmatism.
Geochemical signatures play a vital role in identifying these interactions, providing information about magma sources and mixing. Thermal effects, magmatic processes, and geophysical observations all contribute to our understanding of how plumes shape the Earth's surface and interior.
Plume-lithosphere interaction basics
- Fundamental concept in Isotope Geochemistry explains the interaction between mantle material and overlying lithosphere
- Crucial for understanding the formation of hotspot volcanoes, large igneous provinces, and intraplate magmatism
- Provides insights into mantle composition, dynamics, and thermal structure of the Earth's interior
Definition of mantle plumes
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- Upwelling columns of hot, buoyant material originating from the deep mantle
- Characterized by high temperatures, low viscosity, and distinct geochemical signatures
- Can vary in size, ranging from narrow conduits to large heads (hundreds of kilometers in diameter)
- Often associated with long-lived hotspot tracks on the Earth's surface (Hawaiian-Emperor seamount chain)
Characteristics of lithosphere
- Rigid outer layer of the Earth composed of the crust and uppermost mantle
- Varies in thickness from ~5-70 km for to ~100-250 km for
- Acts as a thermal and mechanical boundary layer in mantle convection
- Exhibits varying physical properties (density, strength, composition) depending on age and tectonic setting
Geochemical signatures
- Isotope Geochemistry plays a crucial role in identifying and characterizing plume-lithosphere interactions
- Geochemical signatures provide information about the source, mixing, and contamination of magmas
- Help distinguish between plume-derived and lithospheric melts in volcanic systems
Isotopic composition of plumes
- Characterized by distinct isotopic ratios (Sr, Nd, Pb, Hf) compared to depleted upper mantle
- Often show elevated ratios indicative of a deep, primordial mantle source
- May exhibit heterogeneities reflecting mixing of different mantle components (primitive mantle, recycled oceanic crust)
- Isotopic compositions can vary between different plumes (HIMU, EM1, EM2 end-members)
Lithospheric contamination effects
- Interaction between plume-derived magmas and lithospheric materials alters original plume signatures
- Can result in mixing trends between plume and lithospheric end-members on isotope diagrams
- of crustal materials may introduce radiogenic Sr and Pb isotopes
- Extent of contamination depends on factors such as magma flux, lithospheric thickness, and residence time
Thermal effects
- Plume-lithosphere interactions significantly impact the thermal structure of the lithosphere
- Understanding thermal effects crucial for interpreting geophysical observations and magmatic processes
- Thermal anomalies associated with plumes can persist for millions of years
Heat transfer mechanisms
- Conduction transfers heat from the hot plume to the cooler lithosphere
- Advection carries heat upward through the movement of magma and fluids
- Latent heat release during crystallization contributes to lithospheric heating
- Radiogenic heat production in the crust can enhance thermal effects
Lithospheric thinning processes
- Thermal erosion removes lithospheric material through heating and weakening
- Mechanical delamination can detach and remove portions of the lithosphere
- Small-scale convection at the base of the lithosphere enhances thinning
- Thinning rates vary depending on plume vigor, lithospheric composition, and tectonic setting
Magmatic processes
- Plume-lithosphere interactions drive complex magmatic processes crucial to Isotope Geochemistry
- Understanding these processes helps interpret geochemical data and reconstruct mantle source characteristics
- Magmatic evolution influenced by factors such as pressure, temperature, and composition
Partial melting dynamics
- Decompression occurs as the plume rises and crosses its solidus
- Degree of partial melting affects trace element concentrations and ratios
- Melting of different mantle components (peridotite, pyroxenite) produces diverse melt compositions
- Lithospheric thickness controls the depth and extent of melting (thicker lithosphere = less melting)
Magma ascent and emplacement
- Buoyancy-driven ascent through fractures and dikes in the lithosphere
- Magma differentiation during ascent through fractional crystallization and assimilation
- Formation of magma chambers at various depths within the crust
- Emplacement as intrusive bodies (plutons, sills) or extrusive volcanic deposits
Geophysical observations
- Geophysical methods provide crucial data for studying plume-lithosphere interactions in Isotope Geochemistry
- Complement geochemical data by providing information on subsurface structure and properties
- Help constrain models of plume dynamics and lithospheric modification
Seismic imaging techniques
- Seismic tomography reveals low-velocity anomalies associated with plumes
- Receiver function analysis detects changes in lithospheric thickness
- Surface wave dispersion maps lateral variations in lithospheric structure
- Body wave travel time analysis identifies mantle transition zone thinning beneath plumes
Gravity and heat flow anomalies
- Positive gravity anomalies often observed over plume-affected regions
- Geoid highs associated with dynamic topography caused by plume buoyancy
- Elevated heat flow measurements indicate thermal perturbations in the lithosphere
- Satellite-derived gravity data (GRACE) provides global coverage of plume-related anomalies
Tectonic implications
- Plume-lithosphere interactions significantly impact tectonic processes and plate dynamics
- Understanding these implications crucial for interpreting geological records and reconstructing past tectonic events
- Interactions can lead to both constructive and destructive tectonic phenomena
Lithospheric deformation patterns
- Radial and concentric fracture systems develop around plume impingement sites
- Uplift and doming of the lithosphere create regional topographic swells
- Lithospheric flexure occurs in response to volcanic loading
- Extensional tectonics may develop due to lithospheric thinning and weakening
Intraplate volcanism
- Formation of oceanic island chains (Hawaiian Islands) and seamount provinces
- Development of continental provinces (Deccan Traps, Columbia River Basalts)
- Reactivation of pre-existing tectonic structures by plume-related stresses
- Long-lived volcanic centers persist due to continued plume activity (Yellowstone)
Temporal evolution
- Plume-lithosphere interactions evolve over geological timescales
- Understanding temporal changes crucial for interpreting geochemical and geophysical data
- Evolution influenced by factors such as plate motion, plume flux, and lithospheric properties
Plume initiation vs maturity
- Initial plume impact characterized by high magma flux and widespread volcanism
- Large igneous provinces form during early stages of plume activity
- Mature plumes show decreased magma production and more focused volcanism
- Geochemical signatures may evolve from initial plume-dominated to more lithosphere-influenced compositions
Long-term lithospheric modification
- Gradual thinning and weakening of the lithosphere over millions of years
- Development of lithospheric drips or delamination events
- Changes in crustal composition due to magmatic underplating and intrusion
- Thermal and compositional modifications persist long after plume activity ceases
Global examples
- Studying diverse plume-lithosphere interactions worldwide provides insights into mantle dynamics and composition
- Comparison of different settings helps identify common processes and unique characteristics
- Global examples crucial for developing and testing models in Isotope Geochemistry
Hawaii vs Iceland
- Hawaii represents a classic intraplate oceanic hotspot with a well-defined age progression
- Iceland forms at the intersection of a plume and mid-ocean ridge, resulting in anomalously thick crust
- Hawaiian lavas show strong ocean island basalt (OIB) signatures
- Icelandic lavas exhibit a mixture of OIB and mid-ocean ridge basalt (MORB) characteristics
Continental vs oceanic settings
- Continental settings (Yellowstone) involve interaction with thick, compositionally diverse lithosphere
- Oceanic settings (Galapagos) interact with thinner, more homogeneous lithosphere
- Continental plumes often produce more silicic magmas due to crustal contamination
- Oceanic plumes typically generate more mafic compositions with less lithospheric influence
Analytical methods
- Advanced analytical techniques in Isotope Geochemistry essential for studying plume-lithosphere interactions
- Precise measurements of isotopic ratios and trace element concentrations provide key data
- Continuous improvement in analytical methods enhances our understanding of mantle processes
Isotope geochemistry techniques
- Thermal Ionization Mass Spectrometry (TIMS) for high-precision Sr, Nd, and Pb isotope ratios
- Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) for Hf and Os isotopes
- Noble gas mass spectrometry for He, Ne, and Ar isotopic compositions
- In-situ techniques (SIMS, LA-ICP-MS) for isotopic analysis of individual minerals and melt inclusions
Trace element analysis
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for precise trace element concentrations
- X-ray Fluorescence (XRF) for major and some trace element analysis
- Electron Microprobe (EPMA) for in-situ major and minor element analysis of minerals
- ICP-MS for high-resolution trace element mapping in minerals and glasses
Modeling approaches
- Numerical and analog modeling crucial for understanding complex plume-lithosphere interactions
- Models help test hypotheses and predict outcomes of different scenarios
- Integration of geochemical and geophysical data improves model accuracy and relevance
Numerical vs analog models
- Numerical models use computer simulations to solve governing equations of fluid dynamics and heat transfer
- Analog models employ physical materials (wax, syrup) to simulate mantle and lithospheric behavior
- Numerical models allow for complex 3D simulations with realistic rheologies
- Analog models provide visual representations and can capture some non-linear behaviors
Geodynamic simulations
- Finite element models simulate thermal and mechanical aspects of plume-lithosphere interaction
- Thermochemical convection models incorporate compositional heterogeneities in the mantle
- Coupled models integrate magma dynamics, crustal processes, and surface deformation
- Particle-in-cell methods track chemical tracers to model geochemical evolution
Implications for mantle dynamics
- Plume-lithosphere interactions provide valuable insights into deep Earth processes
- Understanding these interactions crucial for developing comprehensive models of mantle dynamics
- Integrating geochemical and geophysical observations helps constrain mantle properties and behavior
Mantle convection patterns
- Plumes represent upwelling limbs of mantle convection cells
- Interaction with plates and subduction zones influences global mantle flow patterns
- Small-scale convection at the base of the lithosphere enhances heat and mass transfer
- Plume distribution may reflect deeper mantle structures and compositional heterogeneities
Deep Earth structure insights
- Plume geochemistry provides information on the composition of deep mantle reservoirs
- Seismic imaging of plumes helps constrain thermal and compositional variations in the lower mantle
- Plume-related volcanism samples materials from various mantle depths
- Long-lived plumes may originate from the core-mantle boundary, providing insights into this enigmatic region
Key Terms to Review (18)
Assimilation: Assimilation refers to the process by which a substance or organism integrates and incorporates material from its surroundings into its own structure or composition. This concept is essential in various scientific contexts, as it describes how elements or compounds are absorbed and modified within different systems, impacting the overall behavior and characteristics of these systems.
Continental lithosphere: The continental lithosphere is the rigid outer layer of the Earth, encompassing the crust and the uppermost part of the mantle. This layer varies in thickness and composition, supporting continents and continental features while playing a crucial role in tectonic processes and interactions with underlying mantle materials, especially during phenomena such as plume-lithosphere interactions.
Flood basalt: Flood basalt refers to large-scale volcanic events characterized by the eruption of vast amounts of low-viscosity basaltic lava that spread over extensive areas, forming thick layers of basalt rock. These eruptions can occur over a short geological time frame and are often linked to mantle plumes, which contribute to the formation of large igneous provinces. The relationship between flood basalt events and plume-lithosphere interactions is crucial for understanding the processes that drive such massive volcanic eruptions and their impact on the Earth's surface and atmosphere.
Hot spot: A hot spot is a location on the Earth's surface that experiences volcanic activity due to a mantle plume, which is an upwelling of hot material from deep within the Earth. These areas are often associated with the formation of islands or volcanic chains, such as the Hawaiian Islands, and are crucial for understanding plate tectonics and mantle dynamics.
Isotopic Ratio: Isotopic ratio refers to the relative abundance of different isotopes of the same element in a sample, usually expressed as a fraction or a ratio. This concept is crucial in geochemistry as it helps in understanding processes such as mantle-crust interactions, age dating of geological materials, and tracing the origins of various materials through geological time. In the context of plume-lithosphere interactions, isotopic ratios can reveal the source characteristics of mantle plumes and their interactions with the continental or oceanic lithosphere.
Laser ablation: Laser ablation is a material removal process that uses focused laser energy to vaporize or remove material from a solid surface. This technique is crucial in geochemical analysis, particularly for precise sampling and analysis of solid materials, allowing for the detailed study of isotope compositions in various geological contexts.
Melting: Melting is the process by which a solid becomes a liquid due to the absorption of heat energy, leading to a change in state. This phenomenon is critical in understanding geological processes, as it influences the formation of magma and the differentiation of planetary bodies. When heat is applied, the bonds holding the solid structure together weaken, resulting in the transition to a molten state, which can have significant effects on lithosphere interactions and the overall evolution of planetary systems.
Neodymium-143: Neodymium-143 is a stable isotope of neodymium that plays a critical role in understanding geological processes and the evolution of the Earth's mantle. It is primarily used as an isotopic tracer in geochemistry, especially in studies related to mantle differentiation, crust-mantle interactions, and as a part of the samarium-neodymium (Sm-Nd) dating system to determine the ages of rocks and minerals.
Oceanic lithosphere: The oceanic lithosphere is the outermost layer of the Earth's structure beneath the oceans, composed of the crust and the uppermost mantle. This layer is relatively thin, usually about 5 to 10 kilometers thick, and is primarily made up of basaltic rocks. It plays a crucial role in tectonic processes and interacts with mantle plumes, which can influence geological features and phenomena such as seafloor spreading and volcanic activity.
Plume head model: The plume head model describes a theoretical mechanism by which hot, buoyant material from the mantle rises and creates volcanic activity at the Earth's surface. This model suggests that these mantle plumes originate from deep within the Earth, where they form a mushroom-shaped plume head that can cause significant lithospheric melting and contribute to the development of hotspot volcanism.
Plume tail model: The plume tail model describes the structure and dynamics of mantle plumes, particularly focusing on how these plumes interact with the lithosphere. It illustrates that a plume consists of a hot, rising column of mantle material that can spread out horizontally once it reaches the base of the lithosphere, creating a tail that can influence tectonic activity and surface volcanism.
Radiogenic isotope analysis: Radiogenic isotope analysis is a technique used to measure the abundance of isotopes that are produced through radioactive decay in geological and environmental samples. This method helps to understand the age, source, and processes of various materials by analyzing the ratios of parent isotopes to their decay products. It plays a critical role in deciphering geological histories and plume-lithosphere interactions by providing insights into mantle sources and the evolution of crustal materials.
Strontium-87: Strontium-87 is a stable isotope of strontium that plays a significant role in geochemical processes, particularly in understanding the evolution of the Earth's mantle and crust. This isotope is commonly used as a tracer in various geological studies, helping scientists unravel the complexities of mantle dynamics, the interactions between volcanic plumes and the lithosphere, and even dating techniques like isochron dating. Its importance extends to lunar geochemistry, where it aids in the analysis of extraterrestrial materials.
Super plume: A super plume is a large, buoyant upwelling of hot material from the Earth's mantle that can influence tectonic processes and surface geology. These plumes are characterized by their massive size and ability to impact the lithosphere, leading to volcanic activity and the formation of large igneous provinces, as well as affecting mantle convection and plate tectonics.
Thermal conductivity: Thermal conductivity is a physical property of materials that measures the ability to conduct heat. It is essential for understanding how heat moves through different layers of the Earth, particularly in relation to geophysical processes like plume-lithosphere interactions, where hot material from the mantle influences the thermal state of the overlying lithosphere.
Trace element enrichment: Trace element enrichment refers to the increased concentration of trace elements in specific geological settings, often due to processes such as magmatic differentiation, hydrothermal alteration, or sedimentary deposition. This phenomenon can reveal important information about the sources of magmas and the conditions under which they formed, impacting our understanding of mantle dynamics and crustal evolution.
Upwelling: Upwelling is the process where cold, nutrient-rich water rises from the deep ocean to the surface, often enhancing marine productivity and influencing local ecosystems. This phenomenon typically occurs along coastlines and in certain oceanic regions, driven by wind patterns, ocean currents, and the Earth's rotation. The nutrients brought to the surface support diverse marine life, playing a critical role in food webs and fisheries.
Volcanic arc: A volcanic arc is a chain of volcanoes formed above a subduction zone where an oceanic plate is being pushed under a continental plate. These arcs are characterized by their alignment parallel to the trench created at the subduction zone and often produce explosive eruptions due to the interaction of water and magma. Volcanic arcs are significant in understanding plate tectonics and the geological processes that lead to volcanic activity.