Genetic Diversity Enhances Restoration Success by Augmenting Ecosystem Services

Disturbance and habitat destruction due to human activities is a pervasive problem in near-shore marine ecosystems, and restoration is often used to mitigate losses. A common metric used to evaluate the success of restoration is the return of ecosystem services. Previous research has shown that biodiversity, including genetic diversity, is positively associated with the provision of ecosystem services. We conducted a restoration experiment using sources, techniques, and sites similar to actual large-scale seagrass restoration projects and demonstrated that a small increase in genetic diversity enhanced ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). In our experiment, plots with elevated genetic diversity had plants that survived longer, increased in density more quickly, and provided more ecosystem services (invertebrate habitat, increased primary productivity, and nutrient retention). We used the number of alleles per locus as a measure of genetic diversity, which, unlike clonal diversity used in earlier research, can be applied to any organism. Additionally, unlike previous studies where positive impacts of diversity occurred only after a large disturbance, this study assessed the importance of diversity in response to potential environmental stresses (high temperature, low light) along a water–depth gradient. We found a positive impact of diversity along the entire depth gradient. Taken together, these results suggest that ecosystem restoration will significantly benefit from obtaining sources (transplants or seeds) with high genetic diversity and from restoration techniques that can maintain that genetic diversity

Rare earth elements and Sm-Nd isotope redistribution in apatite and accessory minerals in retrogressed lower crust material (Bergen Arcs, Norway)

In the Bergen Arcs (Norway), Grenvillian granulite retrogressed under eclogite- and amphibolite-facies conditions during Caledonian subduction/collision offer a unique opportunity to investigate rare earth elements (REE) and Sm-Nd isotope redistribution in accessory minerals during fluid-assisted metamorphism. Our sampling targeted apatite-bearing REE-rich protoliths (mangerite and jotunite) that preserve distinct mineral assemblages, depending on the external fluid availability and metamorphic conditions. REE concentrations in apatite are the highest in the granulite. Two populations are present: magmatic apatite (Ap1) relics that occur as inclusions in ilmenite-hematite, and intergranular apatite (Ap2) formed under granulite-facies conditions. The presence of abundant needle-like monazite and sulphide inclusions in Ap2 indicate that granulite reactions were fluid assisted. A thin (typically < 10 μm) rim of REE-rich epidote (Ep1) commonly surrounds Ap2. In these accessory minerals, U and Th contents are too low, or grains are too small, for in situ U-Th-Pb dating. Sm-Nd isotope data of Ap2, monazite and Ep1 give an isochron age of 601 ± 69 Ma, which is interpreted to represent a partially reset Grenvillian age, affected by Caledonian fluid-assisted mineral growth. In amphibolitized samples, granulite Ap2 is replaced by apatite (Ap3) with lower REE contents and no monazite inclusions. The REE released by this replacement are redistributed in a corona of epidote group minerals (Ep2) surrounding Ap3. The in situ Sm-Nd isotope data for Ep2 and titanite, found in replacement of ilmenite-hematite, return an isochron age of 395 ± 65 Ma, recording the timing of amphibolite-facies mineral growth when fluids were introduced into the rock. In eclogitized samples, eclogitic apatite (Ap4) occurs as polycrystalline aggregates, suggesting for a complex replacement process during deformation. REE contents of Ap4 are low, as REE originally contained in the precursor apatite were redistributed mainly into zoisite. Apatite shielded as inclusions in ilmenite and garnet preserve the REE-rich signature of the initial magmatic (Ap1) and granulite (Ap2) apatite, indicating these grains did not undergo further re-equilibration during Caledonian metamorphism. The resistance of apatite to compositional re-equilibration in this case confirms the petrological potential of apatite inclusions shielded in chemically inert minerals to track early magmatic, or metamorphic, crystallisation stages.Emilie Janots, Håkon Austrheim, Carl Spandler, Johannes Hammerli, Claudia A. Trepmann, Jasper Berndt, Valérie Magnin, Anthony I.S. Kem

Sulfur isotope signatures in the lower crust: A SIMS study on S-rich scapolite of granulites

© 2017 Elsevier B.V. Scapolite is an important reservoir for volatiles in the deep crust and provides unique insights into the S isotope signatures at the mantle/crust interface. Here we document the first scapolite reference material (herein referred to as CB1) for in situ S isotope analysis. The chemical and isotopic composition of this euhedral, S-rich scapolite megacryst was characterized via LA-ICP-MS, EPMA, SIMS, and bulk fluorination gas source isotope ratio mass spectrometry. The CB1 scapolite is isotopically homogeneous and our results show that crystal orientation does not affect in situ S isotope SIMS analysis. This makes CB1 an ideal primary calibration standard for in situ analysis of S isotope ratios (36S/32S,34S/32S and33S/32S) in scapolite. With this reference material in hand, we then applied in situ SIMS analysis of S isotopes for the first time on scapolite in granulite samples from the lower crust/upper mantle. The analysed sample suite comprises rocks from classic granulite xenolith locations in southeastern Australia, as well as a sample from the high-grade suture zone of the Dahomeyides in south-eastern Ghana. The results show that scapolites in the lower crust have d34S values between ~- 0.5 and + 4 (‰ VCDT). These values fall within the range of S isotope signatures present in mantle rocks and provide no evidence for the recycling of seawater-derived S into the lower crust. We propose that scapolite formed during granulite facies metamorphism of igneous cumulates, where S was sourced from precursor igneous sulfides. Sulfur isotope heterogeneities between individual scapolite grains in some of the studied samples may reflect non-uniform S-isotope compositions of igneous S-phases, which precipitated from mantle-derived melt

Tracing sulfur sources in the crust via SIMS measurements of sulfur isotopes in apatite

We present a refined approach for acquiring sulfur (S) isotope compositions (33S/32S, 34S/32S) in apatite by secondary ion mass spectrometry (SIMS), including the characterisation of new reference materials. In order to test the method, we analyzed potential apatite reference samples for their S isotope ratios via three different bulk methods. The investigated apatite samples contain S concentrations between ~160 μg/g and 3100 μg/g and their 34S/32S (δ34S) ratios deviate by more than 25‰ from the Vienna-Canyon Diablo Troilite (VCDT) standard. We identified four candidates as new primary reference materials for routine SIMS S isotope measurements of apatite. Based on ICP-MS, EA-IRMS, and fluorination analyses, recommended S isotope values are +12.27± 0.22 (2σ) ‰ δ34S for SAP1, +14.02 ± 0.22 (2σ) ‰ δ34S for Big1, δ34S 1.06 ± 0.80 (2σ) ‰ δ34S for Durango-A, and δ34S 1.39 ± 0.48 (2σ) ‰ for Durango-B. By selecting one of those four primary standards for SIMS analysis, the S isotope values of the other reference materials and additional tested apatite specimens can be reproduced to within 1‰. Under optimized SIMS conditions, single spot uncertainty for δ34S that combines the within-spot precision and the repeatability of measurements of the primary apatite reference material during an analytical session is ±0.4‰ (95% CI). We also show that in apatite with S > 1000 μg/g, SIMS analysis permits the detection of mass independent S isotope signatures (i.e., Δ33S) that are larger than ~1.0‰ if an average of multiple grains is used, and larger than ~1.5‰ for a single analytical point. Furthermore, our study shows that apatite can record S isotope signatures from extremely diverse environments, making this near-ubiquitous mineral a key candidate for tracing S source reservoirs and to track the pathway of magmatic-hydrothermal fluids in a wide range of geological settings

The origin of the sediment-hosted Kanmantoo Cu-Au deposit, South Australia: Mineralogical considerations

Multiply deformed sediments of the Cambrian Kanmantoo Group, which were metamorphosed to the amphibolite facies, host numerous Cu-Au, Fe-S, and Pb-Zn-Ag-(Cu-Au) deposits, of which the largest Cu-Au deposit is Kanmantoo (34.5 Mt @ 0.6% Cu and 0.1 g/t Au). Mineralization at Kanmantoo is characterized by discordant and pipe-like orebodies (Kavanagh and Emily Star) along with mineralization locally concordant to bedding (Nugent) that is spatially related to meta-exhalative rocks. Previous studies have suggested a syn-sedimentary origin for the Pb-Zn-Ag-(Cu-Au) and Fe-S deposits, whereas the Kanmantoo deposit remains controversial, with syn-sedimentary, metamorphogenic, and post-peak metamorphic models having being applied. The stratiform nature of some parts of the Nugent orebody, and disseminated sulfides locally concordant to bedding along with the recognition of a zone of chalcopyrite-magnetiterich rocks at the syn-sedimentary Wheal Ellen Pb-Zn-Ag-(Cu-Au) deposit, which shows a metallic mineral assemblage almost identical to the most common assemblage at Kanmantoo, supports a genetic link between the Pb-Zn-Ag-(Cu-Au) deposits and Cu-Au mineralization, and is consistent with a metamorphosed syn-sedimentary model for Cu-Au mineralization. The discordant nature of most orebodies at Kanmantoo is the result of the mineralization having formed as stockwork zones in sub-seafloor pipes. Varying degrees of remobilization were subsequently associated with syn- to post-peak metamorphism. Major and trace element compositions, coupled with principal component analyses, show that the compositions of garnet, biotite, staurolite, chlorite, muscovite, and magnetite in metamorphosed altered rocks spatially associated with sulfide mineralization at Kanmantoo can be distinguished from those, where present, in metamorphosed country rocks (i.e., metapsammites and metapelites). Garnet, chlorite, biotite, and muscovite in quartz garnetite within quartz mica schist associated with the Nugent orebody are elevated in Mn (up to 19.5wt% MnO – garnet, 2,825 ppm – chlorite, 3,206 ppm – biotite, and 108 ppm – muscovite) and Zn (up to 170 ppm – garnet, 1,602 ppm – chlorite, 1,592 ppm – biotite, and 108 ppm – muscovite) relative to samples in other orebodies and in unmineralized rocks elsewhere in the Kanmantoo Group. Such enrichments in these elements mimic similar enrichments in the same minerals in metamorphosed altered rocks associated with Pb-Zn-Ag-(Cu-Au) deposits in the Kanmantoo Group. Biotite in metamorphosed altered rocks at Kanmantoo contains elevated concentrations of Pb (up to 110 ppm), and, in general, Zn (up to 841 ppm), whereas muscovite is also elevated in Pb, Zn, and Cu (up to 272 ppm Pb, 78 ppm Zn, and 173 ppm Cu). Staurolite in these same rocks contains up to 1.6wt% ZnO (with one outlier that contains 3.2wt%ZnO) and is considerably more enriched in Zn than in unaltered country rocks (∼0.1wt% Zn). The trace element enrichments in silicates studied here constitute a potential pathfinder to metamorphosed Cu-Au mineralization in the Kanmantoo Group and emphasize the geochemical and genetic links between the Pb-Zn-Ag-(Cu-Au) and Cu-Au deposits