Trace elements in anatectic products at the roof of mid-ocean ridge magma chambers: An experimental study

2017 ◽  
Vol 456 ◽  
pp. 43-57 ◽  
Author(s):  
Martin Erdmann ◽  
Lydéric France ◽  
Lennart A. Fischer ◽  
Etienne Deloule ◽  
Jürgen Koepke
Keyword(s):  
Experimental Study ◽  
Trace Elements ◽  
Magma Chambers ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Petrogenetic insights from chromite in ultramafic cumulates of the Xiarihamu intrusion, northern Tibet Plateau, China

2020 ◽  
Vol 105 (4) ◽  
pp. 479-497 ◽  
Author(s):  
Xie-Yan Song ◽  
Kai-Yuan Wang ◽  
Stephen J. Barnes ◽  
Jun-Nian Yi ◽  
Lie-Meng Chen ◽  
...  
Keyword(s):  
Trace Elements ◽  
Major And Trace Elements ◽  
Tibet Plateau ◽  
Ultramafic Rocks ◽  
Sulfide Deposit ◽  
Northern Tibet ◽  
Mid Ocean Ridge ◽  
Ultramafic Cumulates ◽  
Positive Correlations ◽  
Ocean Ridge

Abstract Chromite is one of the earliest crystallized minerals from mafic melts and has been used as an important “petrogenetic indicator.” Its composition may be modified by interaction with intercumulate melt and adjacent minerals. Thus, chromite in mafic-ultramafic rocks contains clues to the geochemical affinity, evolution, and mantle source of its parent magmas. The Devonian Xiarihamu intrusion, located in the East Kunlun Orogenic Belt in the northern Tibet Plateau, China, hosts a very large disseminated Ni-Co sulfide deposit. This study focuses on geochemistry of the chromite enclosed in olivine of ultramafic rocks of the intrusion. Enrichments in Mg and Al in the rim of the chromite indicate only minor effects of alteration on the compositions of the chromite. The chromites enclosed in the olivines with forsterite percentage (Fo) lower than 87 are characterized by large variations in major and trace elements, such as large ranges of Cr·100/(Cr+Al) (Cr# = 15–47), Mg·100/(Mg+Fe2+) (Mg# = 41–65), and Al2O3 (= 26–53 wt%) as well as 380–3100 ppm V, 70–380 ppm Ga, and 1100–16300 ppm Zn. The chromites display positive correlations between Cr/(Cr+Al) and Ti, Mn, V, Ga, and Sc, inconsistent with fractional crystallization but indicative of an interaction between the chromites, intercumulate melts and hosting minerals. In contrast, chromites hosted in olivine with Fo > 87 in harzburgite have small variations in Cr# (ranging from 37 to 41), Mg# (48 to 51), and Al2O3 (30 to 35 wt%) as well as restricted variation in trace elements, indicating relatively weak interaction with trapped liquid and adjacent phases; these compositions are close to those of the most primitive, earliest crystallized chromites. The most primitive chromite has similarities with chromite in mid-ocean ridge basalt (MORB) in TiO2 and Al2O3 contents (0.19–0.32 and 27.9–36.3 wt%, respectively) and depletion of Sc and enrichment of Ga and Zn relative to MORB chromite. The geochemistry of the chromite indicates a partial melting of the asthenospheric mantle that was modified by melts derived from the subduction slab at garnet-stable pressures.

The origin of compositional variation in basalts recovered by submersible drill from Mount Glooscap, Mid-Atlantic Ridge at 36°25′N

1984 ◽  
Vol 21 (8) ◽  
pp. 934-948 ◽  
Author(s):  
James A. Walker ◽  
Patrick J. C. Ryall ◽  
Marcos Zentilli ◽  
Ian L. Gibson ◽  
Jarda Dostal
Keyword(s):  
Trace Elements ◽  
Low Temperature ◽  
Carbonate Rocks ◽  
Compositional Data ◽  
Major And Trace Elements ◽  
Compositional Variation ◽  
Mid Ocean Ridge ◽  
Mid Atlantic Ridge ◽  
Large Peak ◽  
Ocean Ridge

A large peak in the crestal mountains of the Mid-Atlantic Ridge, about 16 km west of the AMAR rift valley at 36°25′N, was sampled for basalt with a submersible electric rock core drill on a comparable surficial scale as the FAMOUS area. Twenty-eight basalt samples from seven drilling stations have been analyzed for major and trace elements. Many of the samples come from flows lying under a cover of carbonate rocks and therefore could not have been sampled by a submersible or a dredge.Through comparisons with published compositional data, it appears that, unlike "FAMOUS-generated" basalts, "AMAR-generated" basalts are, on average, more evolved and are always LREE enriched. Most of the in- and between-hole compositional variation can be accounted for by low-temperature alteration, accumulation of phenocrysts, and low-pressure, relatively low-temperature fractional crystallization. A source heterogeneous in trace elements or undergoing variable degrees of partial melting is necessary to explain the remaining compositional variation. If the large peak can be interpreted as a single volcano, it may be that lavas become progressively more differentiated with time at mid-ocean ridge volcanoes as they commonly do at subduction zone volcanoes.

scholarly journals Reaction Between Mid‐Ocean Ridge Basalt and Lower Oceanic Crust: An Experimental Study

2019 ◽  
Vol 20 (9) ◽  
pp. 4390-4407 ◽  
Author(s):  
Alexandra Yang Yang ◽  
Chunguang Wang ◽  
Yan Liang ◽  
C. Johan Lissenberg
Keyword(s):  
Experimental Study ◽  
Oceanic Crust ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Lower Oceanic Crust

Coupled major and trace elements as indicators of the extent of melting in mid-ocean-ridge peridotites

Nature ◽  
2001 ◽  
Vol 410 (6829) ◽  
pp. 677-681 ◽  
Author(s):  
Eric Hellebrand ◽  
Jonathan E. Snow ◽  
Henry J. B. Dick ◽  
Albrecht W. Hofmann
Keyword(s):  
Trace Elements ◽  
Major And Trace Elements ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Mid-ocean ridge magma chambers

1992 ◽  
Vol 97 (B1) ◽  
pp. 197 ◽  
Author(s):  
John M. Sinton ◽  
Robert S. Detrick
Keyword(s):  
Magma Chambers ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

scholarly journals A Disequilibrium Reactive Transport Model for Mantle Magmatism

2020 ◽  
Author(s):  
Beñat Oliveira ◽  
Juan Carlos Afonso ◽  
Romain Tilhac
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Trace Element ◽  
Chemical Evolution ◽  
Reactive Transport ◽  
Major Elements ◽  
Phase Changes ◽  
Scale Model ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Abstract Besides standard thermo-mechanical conservation laws, a general description of mantle magmatism requires the simultaneous consideration of phase changes (e.g. from solid to liquid), chemical reactions (i.e. exchange of chemical components) and multiple dynamic phases (e.g. liquid percolating through a deforming matrix). Typically, these processes evolve at different rates, over multiple spatial scales and exhibit complex feedback loops and disequilibrium features. Partially as a result of these complexities, integrated descriptions of the thermal, mechanical and chemical evolution of mantle magmatism have been challenging for numerical models. Here we present a conceptual and numerical model that provides a versatile platform to study the dynamics and nonlinear feedbacks inherent in mantle magmatism and to make quantitative comparisons between petrological and geochemical datasets. Our model is based on the combination of three main modules: (1) a Two-Phase, Multi-Component, Reactive Transport module that describes how liquids and solids evolve in space and time; (2) a melting formalism, called Dynamic Disequilibirum Melting, based on thermodynamic grounds and capable of describing the chemical exchange of major elements between phases in disequilibrium; (3) a grain-scale model for diffusion-controlled trace-element mass transfer. We illustrate some of the benefits of the model by analyzing both major and trace elements during mantle magmatism in a mid-ocean ridge-like context. We systematically explore the effects of mantle potential temperature, upwelling velocity, degree of equilibrium and hetererogeneous sources on the compositional variability of melts and residual peridotites. Our model not only reproduces the main thermo-chemical features of decompression melting but also predicts counter-intuitive differentiation trends as a consequence of phase changes and transport occurring in disequilibrium. These include a negative correlation between Na2O and FeO in melts generated at the same Tp and the continued increase of the melt’s CaO/Al2O3 after Cpx exhaustion. Our model results also emphasize the role of disequilibrium arising from diffusion for the interpretation of trace-element signatures. The latter is shown to be able to reconcile the major- and trace-element compositions of abyssal peridotites with field evidence indicating extensive reaction between peridotites and melts. The combination of chemical disequilibrium of major elements and sluggish diffusion of trace elements may also result in weakened middle rare earth to heavy rare earth depletion comparable with the effect of residual garnet in mid-ocean ridge basalt, despite its absence in the modelled melts source. We also find that the crystallization of basalts ascending in disequilibrium through the asthenospheric mantle could be responsible for the formation of olivine gabbros and wehrlites that are observed in the deep sections of ophiolites. The presented framework is general and readily extendable to accommodate additional processes of geological relevance (e.g. melting in the presence of volatiles and/or of complex heterogeneous sources, refertilization of the lithospheric mantle, magma channelization and shallow processes) and the implementation of other geochemical and isotopic proxies. Here we illustrate the effect of heterogeneous sources on the thermo-mechanical-chemical evolution of melts and residues using a mixed peridotite–pyroxenite source.

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