Microstructural and geochemical constraints on the evolution of deep arc lithosphere

Abstract

Mantle xenoliths from the Sierra Nevada, California, USA, sampled a vertical column (60-120 km) of lithosphere that formed during Mesozoic continental arc magmatism. This lithosphere experienced an anticlockwise P-T-t path resulting in rapid cooling that effectively ''quenched in'' features inherited from earlier high-temperature conditions. Here we combine new mineral chemistry data (water, trace element, and major element concentrations) with mineral crystallographic preferred orientations (CPOs) to investigate the relationship between melt infiltration and deformation. The peridotites record a refertilization trend with increasing depth, starting from shallow, coarse-protogranular, less-melt-infiltrated spinel peridotite with strong, orthorhombic olivine CPO to deep, fine-porphyroclastic, highly melt-infiltrated garnet peridotite with weak, axial-[010] olivine CPO. In contrast to the observed axial-[010] CPOs, subgrain boundary orientations and misorientation axes suggest the dominant activation of the (001)[100] slip system, suggesting deformation under moderately hydrous conditions. After accounting for effects of subsolidus cooling, we see coherent trends between mineral trace element abundance and water content, indicating that melt infiltration led to an increase in water content of the peridotites. However, measured olivine and pyroxene water contents in all peridotites (5-10 and 30-500 wt ppm, respectively) are lower than that required to promote dominant (001)[100] slip system observed in both natural and experimental samples. These results suggest that deformation occurred earlier along the P-T path, probably during or shortly after hydrous melt infiltration. Subsequent rapid cooling at 90 Ma led to water loss from olivine (owing to decreased solubility at low temperature), leaving behind a deep arc lithosphere that remained viscously coupled to the Farallon slab until the opening of the slab window in the late Cenozoic.

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

“…This phenomenon has been widely observed in olivine from mantle xenoliths, recorded in H diffusion profiles across grains [ Demouchy et al ., ; Peslier and Luhr , ; Li et al ., ; Denis et al ., ; Doucet et al ., ; Warren and Hauri , ; Peslier et al ., ; Tian et al ., ]. In contrast, studies on natural samples reveal that pyroxenes may preserve the initial water content [ Peslier et al ., ; Bonadiman et al ., ; Soustelle et al ., ; Gose et al ., ; Warren and Hauri , ; Bizimis and Peslier , ; Chin et al ., ]. A possible explanation for these observations is that H diffusion operates by the fast “proton‐polaron” mechanism in mantle olivine, much faster than in Cpx [ Ferriss et al ., ].…”

“…Previous studies suggested that many mantle peridotites have undergone melt-rock reaction during melt transport [Navon and Stolper, 1987;Bodinier et al, 1990;Niu, 2004]. When enriched melt percolates a depleted peridotite, modal metasomatism [e.g., Le Roux et al, 2007;Soustelle et al, 2009;O'Reilly and Griffin, 2012;Soustelle et al, 2013;Chin et al, 2016], as well as cryptic metasomatism [e.g., Navon and Stolper, 1987;Takazawa et al, 1992;Sen et al, 1993] can occur. The modal metasomatism describes the introduction of new phases to preexisting minerals, such as amphibole, mica, apatite [O'Reilly and Griffin, 2012].…”

“…Most of the water concentration measurements in natural mantle minerals are limited to xenoliths from subcontinental and oceanic lithosphere, mantle wedge, and some peridotite massifs [ Peslier et al ., ; Peslier and Luhr , ; Grant et al ., ; Li et al ., ; Yang et al ., ; Bonadiman et al ., ; Peslier , ; Soustelle et al ., ; Xia et al ., ; Yu et al ., ; Doucet et al ., ; Bizimis and Peslier , ; Demouchy et al ., ; Peslier and Bizimis , ; Peslier et al ., ; Chin et al ., ; Demouchy and Bolfan‐Casanova , ]. The water budget of the uppermost oceanic lithospheric mantle is nevertheless poorly constrained as there was only five previous reports on water contents in abyssal peridotites [ Gose et al ., ; Peslier , ; Schmädicke et al ., ; Warren and Hauri , ; Hesse et al ., ].…”

Olivine fabrics and tectonic evolution of fore‐arc mantles: A natural perspective from the Songshugou dunite and harzburgite in the Qinling orogenic belt, central China

“…The occurrence of olivine B and AG-type-like fabrics in SP-FGD/PCD-NF in a mature and cool subduction zone (Figure 11b) implies that a cold fore-arc lithospheric mantle (T < 9008C) could locally have a relatively low mechanical strength (20-30 MPa, Table 1), so that it can be deformed ductilely at a geologically significant strain rate [Boioli et al, 2015;Demouchy et al, 2013]. In addition to the occurrence in the fore-arc asthenosphere [e.g., Cao et al, 2015;Kneller et al, 2005;Precigout and Almqvist, 2014], B and AG-type fabrics are also thought to widely exist in the lithospheric mantle at a mature fore-arc region [Behr and Smith, 2016;Chin et al, 2016;Precigout and Almqvist, 2014]. However, this proposition of widespread distribution of B and AG-type fabrics in the fore-arc lithospheric mantle is difficult to attest in practice.…”

Evolution of the Josephine Peridotite Shear Zones: 2. Influences on Olivine CPO Evolution

“…Experimental and theoretical studies have proposed that olivine CPO is a function of differential stress and water content (e.g., Jung et al, 2006;Jung & Karato, 2001;Katayama et al, 2004), as well as other parameters such as melt content (e.g., Holtzman et al, 2003;Qi et al, 2018), confining pressure (e.g., Mainprice et al, 2005), temperature (e.g., , preexisting CPO (e.g., Boneh & Skemer, 2014;, and deformation kinematics (e.g., Tommasi et al, 1999). At the low differential stresses (~10 MPa) inferred for flow in the uppermost mantle (e.g., Behr & Hirth, 2014;Chin et al, 2016;Hansen & Warren, 2015), a water-induced transition between texture types is predicted by simple shear experiments at a few hundred ppm H/Si in olivine (e.g., Jung et al, 2006;Katayama et al, 2004), from an A-type texture to an E-type texture associated with slip in the [100] direction on the (001) plane ( Figure 1). However, recent studies by Bernard and Behr (2017) and Bernard et al (2019) on continental mantle xenoliths revealed no discernable relationship between water concentration and these CPO types.…”