Plagioclase Peridotites in Ocean-Continent Transitions: Refertilized Mantle Domains Generated by Melt Stagnation in the Shallow Mantle Lithosphere

Müntener, Othmar; Manatschal, Giänreto; Desmurs, Laurent; Pettke, Thomas

doi:10.1093/petrology/egp087

Cited by 188 publications

(170 citation statements)

References 99 publications

(148 reference statements)

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“…Later, during the Alpine orogeny, the exhumed mantle rocks were first tectonically emplaced within a Late Cretaceous E-W directed nappe stack before being thrusted during the Tertiary collision over the European units forming the present-day Alpine orogen Früh-Green et al 1990;Manatschal et al 2003). The serpentinized peridotites in Totalp are interpreted as derived from fertile subcontinental lithospheric mantle (Manatschal et al 2001;Müntener et al 2010;van Acken et al 2010), similar to other described remnants of fossil OCTs from the Alps (e.g. Platta; Desmurs et al 2002; Malenco in the Italian Alps; Müntener et al 2004).…”

Section: Pre-alpine and Alpine Geological And Thermal Historysupporting

confidence: 57%

Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland

Mateeva¹,

Wolff²,

Manatschal³

et al. 2017

Swiss J Geosci

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Evidence from ultraslow spreading mid-ocean ridges and both fossil and present-day Ocean-Continent Transitions (OCT) demonstrates that mantle serpentinization resulting from the interaction of mantle rock and water during tectonic exhumation is widespread. Observations at white smokers in modern ocean settings suggest that methane produced by serpentinization can support methanotrophic bio-systems, which use methane as the only source of carbon. An important question is whether such bio-systems are more generally pervasive in their association with serpentinized mantle in the subsurface. In this study, we examined whether there is evidence for such a methanotrophic system in exhumed serpentinized mantle at a magma-poor rifted continental margin, by probing for characteristic biological markers in these and associated sedimentary rocks in the Totalp unit of SE Switzerland. This unit represents a remnant of the former OCT of the southern Alpine Tethyan margin and was chosen because of its mild Alpine tectonic and low-grade metamorphic overprint during Alpine orogeny, hence giving potential for the preservation of indigenous organic matter (OM). Totalp samples are characterized by low organic carbon contents of 11-647 ppm. The majority of the samples contain hydrocarbons in the form of n-alkanes in the range C 17 -C 36 . Some sediments contain isoprenoids, for example pristane and phytane and a suite of steranes that are consistent with a marine origin for the OM preserved in the rocks. Traces of marine planktonic and bacterial OM are preserved in the serpentinized mantle and overlying sediments of this ancient Tethyan OCT, but there is no evidence that the OM has been generated from methanotrophic bio-systems.

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Section: Pre-alpine and Alpine Geological And Thermal Historysupporting

confidence: 57%

Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland

Mateeva¹,

Wolff²,

Manatschal³

et al. 2017

Swiss J Geosci

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“…Müntener et al ( , 2009) defined three major types of mantle rocks in the Alpine domain, which can be typified as follow:…”

Section: Mantlementioning

confidence: 99%

“…Examples of this type of mantle rocks (e.g. Plagioclase peridotites) are Lanzo, Corsica, Lower Platta, Internal Ligurides, Chenaillet (for references see Müntener et al 2009). …”

Section: Mantlementioning

confidence: 99%

Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins

Mohn

Manatschal

Müntener

et al. 2010

Int J Earth Sci (Geol Rundsch)

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163

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The discovery of exhumed continental mantle and hyper-extended crust in present-day magma-poor rifted margins is at the origin of a paradigm shift within the research field of deep-water rifted margins. It opened new questions about the strain history of rifted margins and the nature and composition of sedimentary, crustal and mantle rocks in rifted margins. Thanks to the benefit of more than one century of work in the Alps and access to world-class outcrops preserving the primary relationships between sediments and crustal and mantle rocks from the fossil Alpine Tethys margins, it is possible to link the subsidence history and syn-rift sedimentary evolution with the strain distribution observed in the crust and mantle rocks exposed in the distal rifted margins. In this paper, we will focus on the transition from early to late rifting that is associated with considerable crustal thinning and a reorganization of the rift system. Crustal thinning is at the origin of a major change in the style of deformation from high-angle to lowangle normal faulting which controls basin-architecture, sedimentary sources and processes and the nature of basement rocks exhumed along the detachment faults in the distal margin. Stratigraphic and isotopic ages indicate that this major change occurred in late Sinemurian time, involving a shift of the syn-rift sedimentation toward the distal domain associated with a major reorganization of the crustal structure with exhumation of lower and middle crust. These changes may be triggered by mantle processes, as indicated by the infiltration of MOR-type magmas in the lithospheric mantle, and the uplift of the Briançonnais domain. Thinning and exhumation of the crust and lithosphere also resulted in the creation of new paleogeographic domains, the Proto Valais and Liguria-Piemonte domains. These basins show a complex, 3D temporal and spatial evolution that might have evolved, at least in the case of the Liguria-Piemonte basin, in the formation of an embryonic oceanic crust. The re-interpretation of the rift evolution and the architecture of the distal rifted margins in the Alps have important implications for the understanding of rifted margins worldwide, but also for the paleogeographic reconstruction of the Alpine domain and its subsequent Alpine compressional overprint.

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“…The crystallization sequence may be perturbed by assimilation of wall rock (Figure 7d), which could increase crystallization [Kelemen and Aharonov, 1998]. Melt-rock reaction has been documented at the slow to ultraslow spreading SWIR [Seyler et al, 2007;Warren et al, 2009;Warren and Shimizu, 2010] and at ophiolites of inferred slow to ultraslow ridges [Müntener et al, 2010]. Finally, diapiric instabilities (Figure 7e) are expected to be more dominant at slower spreading rate [Lin and Phipps Morgan, 1992], and may take over as origin of focusing at ultraslow spreading [Cannat et al, 2008], although they appear less efficient than permeability barriers at focusing melt at the slow spreading Mid-Atlantic Ridge .…”

Section: Melt Focusing Beneath Ultraslow Ridges: a Different Mechanism?mentioning

confidence: 99%

Generation of permeability barriers during melt extraction at mid‐ocean ridges

Hebert

Montési

2010

Geochem Geophys Geosyst

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[1] Melt focusing at mid-ocean ridges is necessary to explain the narrowness of the zone of crustal accretion and the formation of large but localized on-axis seamounts at slow and ultraslow spreading centers. It has been proposed that melt focusing is facilitated by the presence of a barrier to upward melt migration at the base of the thermal boundary layer (TBL). We assess the development of a melt impermeable boundary by modeling the geochemical evolution and crystallization history of melts as they rise into the TBL of mid-ocean ridges with different spreading rates. A permeability barrier, associated with a crystallization front controlled by the conductive thermal regime, exists for melt trajectories at slow to fast spreading ridges (≥10 mm/yr half rate). The effective lateral scope of the barrier, where the slope of the barrier exceeds a critical value that allows buoyant melt transport to the axis, generally increases with spreading rate. At all distances from the axis at ultraslow ridges and off-axis at slow spreading ridges, the weak crystallization front may prohibit formation of an efficient barrier and lead to the possibility that some fraction of melt may be incorporated into the lithospheric mantle, allowing refertilization. The protracted crystallization history and potential absence of an effective permeability barrier may explain the dearth of volcanism at ultraslow ridges and calls for a revision of lateral melt focusing scenarios at ultraslow spreading rates.

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Plagioclase Peridotites in Ocean-Continent Transitions: Refertilized Mantle Domains Generated by Melt Stagnation in the Shallow Mantle Lithosphere

Cited by 188 publications

References 99 publications

Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland

Preserved organic matter in a fossil Ocean Continent Transition in the Alps: the example of Totalp, SE Switzerland

Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins

Generation of permeability barriers during melt extraction at mid‐ocean ridges

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