Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

Leuthold, Julien; Lissenberg, C. Johan; O’Driscoll, Brian; Karakaş, Özge; Falloon, Trevor J.; Klimentyeva, Dina; Ulmer, Peter

doi:10.3389/feart.2018.00015

Cited by 33 publications

(24 citation statements)

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“…This ratio is in rather good agreement with the dissolved Pl/Ol ratios determined by Yang et al (2019) and the faster dissolution of Pl compared to Ol suggested by Donaldson (1985). The equation itself is also consistent with AFC equations previously established from lower oceanic crust samples (e.g., Lissenberg and Dick, 2008;Leuthold et al, 2018). In addition, we used the REE partition coefficients calculated for the average compositions of Ol, Pl, and Cpx analyzed in the Lower unit using the composition-dependent models described above at 1,100°C.…”

Section: Evolution Of Melts Within the Lower Unitsupporting

confidence: 89%

“…The results show that Cpx Ti contents and Mg# expected after FC are both lower than the actual content of the minerals from both the Lower and the Upper unit ( Figure 8A). These geochemical signatures have already been interpreted as evidence for the occurrence of RPF in lower oceanic crustal sections (e.g., Lissenberg and Dick, 2008;Lissenberg and MacLeod, 2016;Leuthold et al, 2018). High-Mg# and Ti Cpx were also identified by Yang et al (2019) in the products of interaction experiments between MORB-type melts and a troctolite analog ( Figure 8A).…”

Section: Role Of Reactive Porous Flow In the Formation And Evolution mentioning

confidence: 55%

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Magma Reservoir Formation and Evolution at a Slow-Spreading Center (Atlantis Bank, Southwest Indian Ridge)

et al. 2020

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Section: Evolution Of Melts Within the Lower Unitsupporting

confidence: 89%

Section: Role Of Reactive Porous Flow In the Formation And Evolution mentioning

confidence: 55%

Magma Reservoir Formation and Evolution at a Slow-Spreading Center (Atlantis Bank, Southwest Indian Ridge)

et al. 2020

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“…3). This small-scale heterogeneity can be explained by multiple replenishments in the crystal mush leading to dissolution-crystallization episodes 17 and juxtaposition of diverse populations of crystals 18 . At the grain scale, cores show more primitive compositions (higher Mg# in clinopyroxene and anorthite content in plagioclase) than rims (see Supplementary Fig.…”

Section: High Magnitude Small-scale Heterogeneity In Cumulate Mineralsmentioning

confidence: 99%

Highly heterogeneous depleted mantle recorded in the lower oceanic crust

et al. 2019

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The Earth's mantle is heterogeneous as a result of early planetary differentiation and subsequent crustal recycling during plate tectonics. Radiogenic isotope signatures of midocean ridge basalts have been used for decades to map mantle composition, defining the depleted mantle end member. These lavas, however, homogenize via magma mixing and may not capture the full chemical variability of their mantle source. Here we show that the depleted mantle is significantly more heterogeneous than previously inferred from the compositions of lavas at the surface, extending to highly enriched compositions. We perform high spatial resolution isotopic analyses on clinopyroxene and plagioclase from lower crustal gabbros drilled on a depleted ridge segment of the northern Mid-Atlantic Ridge. These primitive cumulate minerals record nearly the full heterogeneity observed along the northern Mid-Atlantic Ridge, including hotspots. Our results demonstrate that substantial mantle heterogeneity is concealed in the lower oceanic crust and that melts derived from distinct mantle components can be delivered to the lower crust on a centimetre scale. These findings provide a starting point for re-evaluation of models of plate recycling, mantle convection, and melt transport in the mantle and the crust. The mantle, Earth's largest geochemical reservoir and main source of volcanism, records the timeintegrated history of recycling of oceanic lithosphere and its overlying sediments during the plate tectonic cycle 1,2. The compositional heterogeneity thus generated within the mantle reflects this

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“…Further evidence is present in the plutonic sections of ophiolites (Basch et al, , ; Bédard, ; Bedard et al, ; Rampone et al, ; Sanfilippo, Tribuzio, et al, ). The samples revealed complex zoning patterns, reaction textures, and mineral compositions and modes that could not be explained by fractional crystallization: instead, the data suggest that melt‐mush reaction is a common process in the lower oceanic crust (Coogan, Saunders, et al, ; Dick et al, ; Gao et al, ; Leuthold et al, ; Lissenberg et al, ; Lissenberg & MacLeod, ; Meyer et al, ; Ridley et al, ). Such a melt‐mush reaction is also proposed to be common in continental magma systems (e.g., Bédard et al, ; Boudreau, ; Cashman et al, ; Irvine, ; Leuthold et al, ; Leuthold et al, ; Mathez, ; McBirney & Sonnenthal, ; Namur et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Hence, melts and crystals coexist throughout the mid‐ocean ridge magma plumbing system, providing two possible mechanisms for reactions to occur between melts and crystals. The first is during the emplacement of primitive melts into the mush (Kvassnes & Grove, ; Leuthold et al, ). Primitive melts are unlikely to be saturated in (all of) the phases present in the mush in which they are emplaced, leading to partial melting reactions.…”

Section: Introductionmentioning

confidence: 99%

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

Yang

Wang

Liang

et al. 2019

Geochem Geophys Geosyst

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Reaction between mid-ocean ridge basalt (MORB) and crystal mush in the lower oceanic crust has been invoked to explain chemical variations of both MORB and minerals in the lower oceanic crust. Nonetheless, such reactions have been little studied experimentally. We conducted experiments to investigate the mechanisms and chemical consequences of melt-mush interaction by reacting molten MORB with troctolite at 0.5 GPa. Isothermal experiments demonstrate that melt infiltrates into troctolite with dissolution of plagioclase and olivine. The reacted melts have higher MgO and Al 2 O 3 and lower TiO 2 and Na 2 O contents and crystallize more primitive olivine and plagioclase compared to those crystallized from the unreacted melts, suggesting melt-mush reaction could result in the formation of high-Al basalt. The melt compositional variations induced by reaction also significantly affect the calculated pressures for MORB fractionation, indicating that major element-based barometers for MORB fractionation can only be used reliably if reaction can be ruled out. After reaction, the troctolite contains olivine with plagioclase inclusions and poikilitic clinopyroxene with partially resorbed olivine and plagioclase chadacrysts, indicating that melt-mush interaction occurs through dissolution-reprecipitation mechanisms. Clinopyroxene has high Mg# (>83) and elevated Na 2 O and TiO 2 contents, and olivine has different Fo versus Ni correlations from fractional crystallization models, which provide testable parameters for the effect of melt-mush reaction in the rock record. By comparison with samples from lower oceanic crust and layered intrusions, we propose that melt-mush reaction plays an important role during magma transport in the crystal mush in both oceanic and continental magma systems.Plain Language Summary Magmas erupted at mid-ocean ridges represent the largest volcanic output from the Earth's interior and have long been recognized as a probe to mantle composition and melting history. During its ascent from the mantle, magma crystallizes minerals in crustal magma reservoirs. Although crystallization modifies magma compositions, this process is well-understood and can therefore be corrected for. However, when crystallization proceeds, a network of interconnected minerals forms with small amounts of magma between them. Recent studies show that magma compositions might also be modified by reaction with minerals in this so-called crystal mush. Our study, for the first time, performed experiments to explore how such reactions work and how they change the compositions of both magma and minerals. The results show that during reaction, magma can dissolve some minerals and crystallize others, which changes the magma compositions. Such variations in magma compositions challenge our understanding on the histories and depth of magma crystallization derived from them and eventually affect our understanding of mantle composition. We also found that minerals in the mush carry distinct chemical signatures after reaction, which can be us...

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Partial Melting of Lower Oceanic Crust Gabbro: Constraints From Poikilitic Clinopyroxene Primocrysts

Cited by 33 publications

References 81 publications

Magma Reservoir Formation and Evolution at a Slow-Spreading Center (Atlantis Bank, Southwest Indian Ridge)

Magma Reservoir Formation and Evolution at a Slow-Spreading Center (Atlantis Bank, Southwest Indian Ridge)

Highly heterogeneous depleted mantle recorded in the lower oceanic crust

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

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