The fate of accessory minerals and key trace elements during anatexis and magma extraction

This work was financially supported by ARC grant DP110102543.Granite genesis and crustal evolution are closely associated with partial melting in the lower or middle crust and extraction of granite magmas to upper levels. This is generally thought to be the leading mechanism by which the upper continental crust became enriched in incompatible components such as the heat-producing elements U and Th through time. However, field evidence from anatectic terrains, the source rocks of granite magmas, raises doubt about the efficiency of this process. Leucosomes and associated leucogranites, representative of melts in such terrains, are often depleted in U, Th and REE compared to their source and therefore unable to enrich the upper crust in these elements. This paper demonstrates using anatectic turbidites exposed on Kangaroo Island that accessory minerals, the main host of U, Th and REE, become preferentially concentrated in the melanosomes, effectively removing these elements from the melt. Whole rock geochemistry and detailed petrography suggests that (a) peraluminous melts dissolve only small fractions of monazite and xenotime, because efficient apatite dissolution saturates melt early in phosphorous; and (b) local melt–host reaction emerging from melt migration may cause substantial melt to crystallize in the magma extraction channelways in or close to the magma source region. Crystallization causes oversaturation of the magma triggering the crystallization and capture of accessory minerals in the growing biotite-rich selvedge rather than in the melt channel itself. Crystallization of accessory minerals away from the leucosomes explains the apparent under-saturation of elements hosted by these accessory minerals in the leucosome. While intense reworking of thick piles of turbidites, common in accretionary orogens, reflect important processes of crustal formation, the fate of accessory phases and the key elements they control, such as the heat producing elements U and Th, is strongly dependent on the interaction between melt and surrounding solids during segregation and extraction.PostprintPeer reviewe

Quantification of synmagmatic flow structures of the Vila Pouca de Aguiar Pluton, NE Portugal

Methods based on fractal geometry offer the opportunity to quantify complex rock patterns (Kruhl. 2013), which provide information about the pattern forming processes. Mineral distribution patterns of Variscan post-tectonic granites from NE of Portugal (Vila Pouca de Aguiar Pluton) were analyzed with the MORFA and Map-­Counting software (Peternell, 2011). The result of the analysis provides information about pattern inhomogeneity and anisotropy, i.e. magmatic flux directions and mineral equilibrium processes in the crystallizing magma chamber.Fundação para a Ciência e a Tecnologia (FCT

Quantification of synmagmatic flow structures: a tool for Rock Quality Evaluation

The result of the analysis using methods based on fractal geometry provides information about magmatic flux directions and mineral equilibrium processes in the crystallizing magma chamber. Additionally, the used methods may also provide important information for the rock industry, because they allow a fast and automatically evaluation of rock quality.Fundação para a Ciência e a Tecnologia (FCT

Quantification of quartz microstructures

Quartz microstructure analysis based on classical optical microscopy, is appointing to the identification of features related with dominial quartz studies. Microstructural features defined in this study include the concepts of microstructures, microstructural elements, microstructural features, fabric elements, elementary textures, textural elements and textural features (e.g., Vernon, 1976 and Kosaka, 1980). Petrographic analysis was focused on the identification of quartz microstructures, such as intra-granular microstructures, inter-granular boundary, and their relation to the deformation mechanisms activated during a simple shear progressive deformation event. These structures were quantified following the methodology developed by Kosaka (1980). To ensure a random sampling, measurement points were picked from a standard grid that covers the total thin section area. A statistically significant number of points were analysed.Fundação para a Ciência e a Tecnologia (FCT

P-T Path of a Variscan Shear Zone recorded on Quartz-Aluminous Shearband Boudins

The work is focused on the P-T path recorded on internal shearband boudin microstructures, developed during simple shear progressive deformation (Malpica-Lamego Ductile Shear Zone – MLDSZ, NW Portugal). In the studied area, MLDSZ is a NW-SE striking Variscan crustal shear zone with a subvertical and west-dipping foliation and a sub-horizontal stretching lineation; it is recorded as a heterogeneous simple shear zone with bulk left-lateral kinematics (Pamplona and Rodrigues, 2011). The deformation zone is marked by a generalized foliation (Sn) defined by Bt+Ms±Sil and a stretching mineral lineation marked by sillimanite fibres. Microstructural analysis, fluid inclusions studies, Raman spectroscopy, crystallographic preferred orientation on quartz grains and fractal geometry based analysis were applied to the boudins.Fundação para a Ciência e a Tecnologia (FCT

Interpretative model of shearband boudins internal evolution in HT ductile shear zones

The internal structure of a shearband boudin resulting from an original igneous, hydrothermal or metamorphic segregation tabular rigid body is a subject of scientific interest. It allows understanding the deformation mechanisms acting on homogeneous quartz aggregate activated during simple shear progressive deformation. This work is focused on the characterization of the internal evolution of shearband boudins, using microtextural analysis, fluid inclusions studies, fractal and OCP analysis. The proposed interpretative model shows the several structural stages that can be well established during the process of the internal evolution of shearband boudin

Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Richter, M., Nebel, O., Schwindinger, M., Nebel-Jacobsen, Y., & Dick, H. J. B. Competing effects of spreading rate, crystal fractionation and source variability on Fe isotope systematics in mid-ocean ridge lavas. Scientific Reports, 11(1), (2021): 4123, https://doi.org/10.1038/s41598-021-83387-7.Two-thirds of the Earth is covered by mid-ocean ridge basalts, which form along a network of divergent plate margins. Basalts along these margins display a chemical diversity, which is consequent to a complex interplay of partial mantle melting in the upper mantle and magmatic differentiation processes in lower crustal levels. Igneous differentiation (crystal fractionation, partial melting) and source heterogeneity, in general, are key drivers creating variable chemistry in mid-ocean ridge basalts. This variability is reflected in iron isotope systematics (expressed as δ57Fe), showing a total range of 0.2 ‰ from δ57Fe =  + 0.05 to + 0.25 ‰. Respective contributions of source heterogeneity and magma differentiation leading to this diversity, however, remain elusive. This study investigates the iron isotope systematics in basalts from the ultraslow spreading Gakkel Ridge in the Arctic Ocean and compares them to existing data from the fast spreading East Pacific Rise ridge. Results indicate that Gakkel lavas are driven to heavier iron isotope compositions through partial melting processes, whereas effects of igneous differentiation are minor. This is in stark contrast to fast spreading ridges showing reversed effects of near negligible partial melting effects followed by large isotope fractionation along the liquid line of descent. Gakkel lavas further reveal mantle heterogeneity that is superimposed on the igneous differentiation effects, showing that upper mantle Fe isotope heterogeneity can be transmitted into erupting basalts in the absence of homogenisation processes in sub-oceanic magma chambers.This work was supported by an ARC grant FT140101062 to O.N. H.J.B.D was supported by the NSF grants PLR 9912162, PLR 0327591, OCE 0930487 and OCE 1434452

Quantificação das estruturas de fluxo sin-magmáticas do Plutão de Vila Pouca de Aguiar: uma ferramenta para a quantificação estrutural e da qualidade da rocha

Mineral distribution pattern of Variscan post-tectonic granites from Vila Pouca de Aguiar Pluton (NE Portugal) were analyzed with methods partially based on fractal geometry and, with respect to rock inhomogeneity and anisotropy. The result of the analysis provides information about magmatic flux and mineral equilibrium processes in a crystallizing magma chamber. In addition, the used methods may also provide important information for the ornamental rock industry, because they allow fast and automatic evaluation of economic rock parameters.Os padrões de distribuição mineral dos granitos póstectónicos do plutão de Vila Pouca de Aguiar foram analisados com métodos parcialmente baseados na geometria fractal, atendendo à homogeneidade e anisotropia da rocha. O resultado desta análise forneceu informação acerca do fluxo magmático e dos processos de equilíbrio mineral na cristalização no interior de uma câmara magmática. Adicionalmente, os métodos utilizados ainda disponibilizaram informação importante para a indústria de pedra ornamental, pois permitem uma avaliação rápida e automática dos parâmetros que valorizam economicamente a rocha.(undefined

Denosumab treatment for fibrous dysplasia

Fibrous dysplasia (FD) is a skeletal disease caused by somatic activating mutations of the cyclic adenosine monophosphate (cAMP)‐regulating protein, α‐subunit of the Gs stimulatory protein (G s α). These mutations lead to replacement of normal bone by proliferative osteogenic precursors, resulting in deformity, fracture, and pain. Medical treatment has been ineffective in altering the disease course. Receptor activator of NF‐κB ligand (RANKL) is a cell‐surface protein involved in many cellular processes, including osteoclastogenesis, and is reported to be overexpressed in FD‐like bone cells. Denosumab is a humanized monoclonal antibody to RANKL approved for treatment of osteoporosis and prevention of skeletal‐related events from bone metastases. We present the case of a 9‐year‐old boy with severe FD who was treated with denosumab for a rapidly expanding femoral lesion. Immunohistochemical staining on a pretreatment bone biopsy specimen revealed marked RANKL expression. He was started on monthly denosumab, with an initial starting dose of 1 mg/kg and planned 0.25 mg/kg dose escalations every 3 months. Over 7 months of treatment he showed marked reduction in pain, bone turnover markers (BTMs), and tumor growth rate. Denosumab did not appear to impair healing of a femoral fracture that occurred while on treatment. With initiation of treatment he developed hypophosphatemia and secondary hyperparathyroidism, necessitating supplementation with phosphorus, calcium, and calcitriol. BTMs showed rapid and sustained suppression. With discontinuation there was rapid and dramatic rebound of BTMs with cross‐linked C‐telopeptide (reflecting osteoclast activity) exceeding pretreatment levels, accompanied by severe hypercalcemia. In this child, denosumab lead to dramatic reduction of FD expansion and FD‐related bone pain. Denosumab was associated with clinically significant disturbances of mineral metabolism both while on treatment and after discontinuation. Denosumab treatment of FD warrants further study to confirm efficacy and determine potential morbidity, as well as to determine the mechanism of RANKL in the pathogenesis of FD and related bone marrow stromal cell diseases. © 2012 American Society for Bone and Mineral Research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92121/1/1603_ftp.pd