Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

Chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatic–hydrothermal systems such as the Coroccohuayco Fe–Cu–Au porphyry–skarn deposit, Peru. Here, we used recent partitioning models to determine the Cl and S concentration of the melts from the Coroccohuayco magmatic suite using apatite and amphibole chemical analyses. The pre-mineralization gabbrodiorite complex hosts S-poor apatite, while the syn- and post-ore dacitic porphyries host S-rich apatite. Our apatite data on the Coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity (from the gabbrodiorite complex to the porphyries) causing the dominant sulfur species to shift from S2− to S6+ at upper crustal pressure where the magmas were emplaced. We suggest that this change in sulfur speciation could have favored S degassing, rather than its sequestration in magmatic sulfides. Using available partitioning models for apatite from the porphyries, pre-degassing S melt concentration was 20–200 ppm. Estimates of absolute magmatic Cl concentrations using amphibole and apatite gave highly contrasting results. Cl melt concentrations obtained from apatite (0.60 wt% for the gabbrodiorite complex; 0.2–0.3 wt% for the porphyries) seems much more reasonable than those obtained from amphibole which are very low (0.37 wt% for the gabbrodiorite complex; 0.10 wt% for the porphyries). In turn, relative variations of the Cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the Coroccohuayco magmatic suite. This confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement, and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100–200 MPa. Finally, mass balance constraints on S, Cu and Cl were used to estimate the minimum volume of magma required to form the Coroccohuayco deposit. These three estimates are remarkably consistent among each other (ca. 100 km3) and suggest that the Cl melt concentration is at least as critical as that of Cu and S to form an economic mineralization

Auswirkungen atmosphärischer Stickstoffeinträge auf magere Flachland-Mähwiesen in Baden-Württemberg

Atmosphärische Stickstoffeinträge in naturnahe Ökosysteme stellen für Lebensraumtypen (LRT) der Fauna-Flora-Habitat-Richtlinie (FFH-Richtlinie) eine Gefährdung dar. Auch der Erhaltungsgrad der artenreichen, in Südwestdeutschland weit verbreiteten mageren Flachland-Mähwiesen (LRT 6510) hat sich verschlechtert. Ursachen hierfür können Bewirtschaftungsaspekte (z.B. Düngung), aber auch atmosphärische (atm.) Immissionen sein. Die in diesem Beitrag vorgestellte Studie untersucht (1) den Zusammenhang zwischen Erhaltungsgrad des LRT 6510 und Artengruppen (Stickstoffzeiger, Magerkeitszeiger) anhand modellierter atm. Ammoniak-(NH3-)Konzentrationen und (2) den Einfluss von Standortfaktoren auf diese Artengruppen. Artenzusammensetzung, relevante Standortfaktoren und modellierte Stickstoffdaten von 10006 Kartiereinheiten des LRT 6510 wurden mittels Generalisierter Linearer Modelle (GLM) analysiert. Die Ergebnisse zeigen, dass (1) mit zunehmender atm. NH3-Konzentration die Anzahl an Magerkeitszeigern abnimmt und die Anzahl an Stickstoffzeigern zunimmt und (2) der Einfluss der Standortfaktoren auf die untersuchten Artengruppen mit diesem Ansatz nur eingeschränkt nachweisbar ist

Tamanho do tubérculo-semente de batata não interfere na manifestação da murcha bacteriana Potato seed tuber size does not interfere with the incidence of potato bacterial wilt

A batata-semente é comercializada no Brasil em diferentes tamanhos, conforme determinação do MAPA, variando do tipo 0 (zero), com tubérculos acima de 60 mm, até o tipo V, com tubérculos menores que 23 mm. Neste trabalho, foi avaliado o efeito do tamanho do tubérculo da batata-semente na manifestação da murcha bacteriana nas cultivares Agata, BRS Ana, Asterix e Bintje, em campo naturalmente infestado com Ralstonia solanacearum, em Brasília-DF. Foram usados tubérculos pequenos, médios e grandes, com aproximadamente 30, 50 e 90 mm em média, tamanhos correspondentes respectivamente aos tipos IV, II e 0 das normas do MAPA. Diferenças significativas quanto à incidência da doença foram encontradas entre cultivares: BRS Ana e Asterix não diferiram entre si e foram mais resistentes que Agata e Bintje que, por sua vez, tampouco diferiram entre si. As diferenças entre tamanhos de tubérculos e as interações entre cultivar e tamanho de tubérculos não foram significativas. Portanto concluiu-se que o tamanho de tubérculos dentro dos limites avaliados neste trabalho, não interferiu na manifestação da doença em testes de avaliação para resistência à murcha bacteriana.<br>Potato seed tubers in Brazil are commercialized in different sizes as determined by the Ministry of Agriculture, Livestock and Food Supply. The sizes are classified in types, which vary from type 0 (zero), tubers above 60 mm, up to type V, tubers below 23 mm. In this work, we evaluated the influence of seed tuber size on the incidence of bacterial wilt on cultivars Agata, BRS Ana, Asterix, and Bintje, grown in a field naturally infested with Ralstonia solanacearum, in Brasilia, Brazil. We used small, medium and large tubers, measuring in average 30, 50 and 90 mm, which correspond respectively to types IV, II and 0 according to the Brazilian legislation. Significant differences in bacterial wilt incidences were detected among cultivars: BRS Ana and Asterix did not differ from each other and were more resistant than Agata and Bintje, which formed a statistically homogeneous pair. Differences on the seed tuber size and interactions between cultivars and tuber size were not significant. Therefore, the seed tuber size, within the limits covered in this paper, have no effect on disease incidence in field screening for potato resistance to the bacterial wilt