Diverse Sr isotope signatures preserved in mid-oceanic-ridge basalt plagioclase

Lange, A.; Nielsen, Roger L.; Tepley, F. J.; Kent, Adam J.R.

doi:10.1130/g33739.1

Cited by 33 publications

(34 citation statements)

References 30 publications

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“…The resulted magmas exhibit transitional properties between different bathes of magmas, commonly having the following geochemical features [e.g., Poli et al ., ; Maclennan et al ., ; Maclennan , ; Davidson et al ., ; Sun et al ., ]: (1) heterogeneous whole‐rock element and isotope compositions; (2) variable element and isotope compositions in single mineral crystals (from core to rim) or between different mineral crystals such as zircon, Cpx, Amp and Pl; (3) variable compositions of mineral inclusions in early crystallized phases. Different 87 Sr/ 86 Sr ratios also occur across Pl phenocrysts and between Pl phenocrysts and groundmass in MORB [ Lange et al ., ], demonstrating the magma mixing of mafic melts derived from partial melting of the heterogeneous asthenospheric mantle. Major and trace element zonations of Cpx and Pl phenocrysts were reported in Icelandic basalts [ Winpenny and Maclennan , ], recording the magma mixing between different batches of oceanic basaltic melts.…”

Section: Discussionmentioning

confidence: 99%

Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

Dai

Zhao

Zheng

et al. 2015

Geochem. Geophys. Geosyst.

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Postcollisional mafic igneous rocks commonly exhibit petrological and geochemical heterogeneities, but their origin still remains enigmatic. While source mixing is substantial due to the crustmantle interaction during continental collision, magma mixing is also significant during postcollisional magmatism. The two processes are illustrated by Early Cretaceous mafic igneous rocks in the Dabie orogen. These mafic rocks show arc-like trace element distribution patterns and enriched Sr-Nd-Pb isotope compositions, indicating their origination from enriched mantle sources. They have variable whole-rock e Nd (t) values of 217.6 to 25.2 and zircon e Hf (t) values of 229.0 to 27.7, pointing to source heterogeneities. Such whole-rock geochemical features are interpreted by the source mixing through melt-peridotite reaction in the continental subduction channel. Clinopyroxene and plagioclase megacrystals show complex textural and compositional variations, recording three stages of mineral crystallization during magma evolution. Cpx-1 core has low Cr and Ni but high Ba, Rb and K, indicating its crystallization from a mafic melt (Melt 1) derived from partial melting of hydrous peridotite rich in phlogopite. Cpx-1 mantle and Cpx-2 exhibit significantly high Cr, Ni and Al 2 O 3 but low Rb and Ba, suggesting their crystallization from pyroxenite-derived mafic melt (Melt 2). Whole-rock initial 87 Sr/ 86 Sr ratios of gabbro lies between those of Pl-1core (crystallized from Melt 1) and Pl-1 mantle and Pl-2 core (crystallized from Melt 2), providing isotopic evidence for magma mixing between Melt 1 and Melt 2. Taken together, a heterogeneously enriched mantle source would be generated by the source mixing due to reaction of the overlying subcontinental lithospheric mantle wedge peridotite with felsic melts derived from partial melting of different rocks of the deeply subducted continental crust during the continental collision. The magma mixing would occur between mafic melts that were derived from partial melting of the heterogeneously metasomatic mantle domains in the postcollisional stage. As a consequence, the source and magma mixing processes in the continental subduction factory are responsible for the significant variations in the whole-rock and mineral geochemistries of postcollisional mafic igneous rocks.

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Section: Discussionmentioning

confidence: 99%

Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

Dai

Zhao

Zheng

et al. 2015

Geochem. Geophys. Geosyst.

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“…Future work to constrain the ages, compositions, and structural relationships of older suites of volcanic products at Axial may address if or how stress state can affect magmatism and crustal morphological evolution, perhaps including caldera formation. Detailed in situ microanalyses of plagioclases and melt inclusions may reveal further insight into crystallization depths and magmatic conditions during genesis and pre‐eruptive processing of plagioclase‐phyric lavas [e.g., Nielsen et al ., ; Lange et al ., ; Zellmer et al ., ; Wanless and Shaw , ] and whether conditions differed between plagioclase‐phyric lavas sourced from the caldera center and rift zones.…”

Section: Discussionmentioning

confidence: 99%

Petrological variability of recent magmatism at Axial Seamount summit, Juan de Fuca Ridge

Dreyer

Clague

Gill

2013

Geochem Geophys Geosyst

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A combined study of mapping, observational, age constraint, and geochemical data at the summit of Axial Seamount, Juan de Fuca Ridge, has revealed its recent petrological history. Multiple basalt types erupted at the summit in a time sequence. At least three different magma batches have been present beneath the Axial Summit caldera during the last millennium, each with a range in differentiation. The first, prior to 1100 CE, was compositionally diverse, dominantly aphyric T‐MORB. The second, from ∼1220 to 1300 CE, was dominantly plagioclase‐phyric, more mafic N‐MORB erupted mostly in the central portion of the caldera. Since ∼1400 CE, lavas have been more differentiated, and nearly aphyric T‐MORB mostly erupted in the caldera's rift zones. Parental magmas vary subtly due to small coupled differences in the degree of melting and sources, but all share a uniform differentiation trend indicating pooling at similar depths. Thus, melts percolate through melt‐rich lenses that remain partially isolated in space and/or time. Centennial magmatic timescales at Axial Seamount are similar to those for fast spreading ridge segments. The fluctuation between aphyric and plagioclase‐phyric lava likely reflects different pathways or velocities of melt migration.

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“…The starting materials for the melt inclusion experiments were a range of plagioclase ultraphyric basalts (PUB) sampled from a number of ridges and pull apart basins (supporting information Figure S2). These samples have been used for a number of previous investigations [Nielsen et al, 1995;Sours-Page et al, 1999;Weinsteiger, 2010;Lange et al, 2012Lange et al, , 2013 focused at the petrogenesis of PUB.…”

Section: Starting Materialsmentioning

confidence: 99%

Trace element partitioning between plagioclase and melt: An investigation of the impact of experimental and analytical procedures

Nielsen

Üstünışık

Weinsteiger

et al. 2017

Geochem Geophys Geosyst

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Quantitative models of petrologic processes require accurate partition coefficients. Our ability to obtain accurate partition coefficients is constrained by their dependence on pressure temperature and composition, and on the experimental and analytical techniques we apply. The source and magnitude of error in experimental studies of trace element partitioning may go unrecognized if one examines only the processed published data. The most important sources of error are relict crystals, and analyses of more than one phase in the analytical volume. Because we have typically published averaged data, identification of compromised data is difficult if not impossible. We addressed this problem by examining unprocessed data from plagioclase/melt partitioning experiments, by comparing models based on that data with existing partitioning models, and evaluated the degree to which the partitioning models are dependent on the calibration data. We found that partitioning models are dependent on the calibration data in ways that result in erroneous model values, and that the error will be systematic and dependent on the value of the partition coefficient. In effect, use of different calibration datasets will result in partitioning models whose results are systematically biased, and that one can arrive at different and conflicting conclusions depending on how a model is calibrated, defeating the purpose of applying the models. Ultimately this is an experimental data problem, which can be solved if we publish individual analyses (not averages) or use a projection method wherein we use an independent compositional constraint to identify and estimate the uncontaminated composition of each phase.

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Diverse Sr isotope signatures preserved in mid-oceanic-ridge basalt plagioclase

Cited by 33 publications

References 30 publications

Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

Source and magma mixing processes in continental subduction factory: Geochemical evidence from postcollisional mafic igneous rocks in the Dabie orogen

Petrological variability of recent magmatism at Axial Seamount summit, Juan de Fuca Ridge

Trace element partitioning between plagioclase and melt: An investigation of the impact of experimental and analytical procedures

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