Quartz from different zones within five granitic pegmatites of the rare-element class from the Borborema Pegmatite Province in northeast Brazil were analysed for fourteen trace elements using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The concentrations of Li (6À150 ppm), B (1À9 ppm) and Ge (1À23 ppm) in quartz show a positive correlation with Al (30À770 ppm). The concentrations of these elements increase from the border zone to the quartz core of pegmatites of the spodumene or lepidolite subtypes. The Ge concentrations in the quartz core are the highest so far reported in igneous quartz. In the less evolved pegmatites of the beryl-columbite subtype, the Al, Li, B, and Ge concentrations in quartz from all zones remain at the same level as the border and wall zones. The Ti concentrations in quartz from the core of the more evolved pegmatites are below 3 ppm (with Al >250 ppm), contrasting with 7À25 ppm (with Al <280 ppm) in samples from the border and wall zones of the less evolved and more evolved pegmatites. The concentrations of Al, Li, B, Ge, and Ti in quartz are therefore confirmed as good indicators of the degree of magma fractionation and analyses of pegmatite quartz cores can be used for exploration purposes to distinguish pegmatites with high metallogenic potential. Atoms of Li and Al are incorporated into quartz such that Li/Al ranges between 0.75 and 1.0. This suggests a coupled substitution of the form Si 4+ $ (Li + + Al 3+ ). The other elements analysed either showed an erratic distribution (e.g. Be and P) or were below the respective limits of detection (Na, K, Rb, Ca, Sr, Mn, Fe) in most samples.

No abstract

The objective of this research is to evaluate the engineering students' perception regarding sustainability. For this, a survey was developed based on sustainability parameters from a detailed analysis of the Global Reporting Initiative (GRI) and the Brazilian Institute of Corporate Governance (IBGC). The parameters were initially divided into seven groups: Financial and Productivity Aspects (FPA); Concern with employees (CWE); Support for Local Communities (SLC); Ethical and corporate governance issues (ECI); Environmental aspects (ENA); Sustainable aspects in the operations network (SON); Customers, development of new products and services (CPS). The survey was conducted with engineering undergraduate students from two Brazilian universities. The data were analyzed through structural equation modeling technique, more precisely by means of the PLS-SEM algorithm. We obtained 162 answers, which enabled the validation of the model tested, and showed that the students, in general, do not consider support for local communities and concern with employees when they are analyzing sustainability. Additionally, the most important construct for them is the customers, development of new products and services. This is an exploratory study and we believe that these findings may contribute to expand the debate about the sustainability insertion in engineering courses, helping educators in their didactic activities. As future research, it is suggested the replication of this study in other higher education institutions.

Abstract-Petrographic and geochemical data obtained on the Araguainha impact crater (Goi as/Mato Grosso States, Brazil) indicate the existence of several molten products that originated during impact-induced congruent melting of an alkali-granite exposed in the inner part of the central uplift of the structure. Although previous studies have described these melts to some extent, there is no detailed discussion on the petrographic and geochemical variability in the granite and its impactogenic derivatives, and therefore, little is known about the geochemical behavior and mobility of trace elements during its fusion in the central part of the Araguainha crater. This paper demonstrates that the preserved granitoid exposed in the core of the structure is a magnesium-rich granite, similar to postcollisional, A-type granites, also found in terrains outside the Araguainha crater, in the Bras ılia orogenic belt. The molten products are texturally distinct and different from the original rock, but have very similar geochemical composition, making it difficult to separate these lithotypes based on concentrations of major and minor elements. This also applies for trace and rare earth elements (REE), thus indicating a high degree of homogenization during impact-induced congruent melting under high pressure and postshock temperature conditions. Petrographic observations, along with geochemical data, indicate that melting occurs selectively, where some of the elements are transported with the melt. Simultaneously, there is an effective dissolution of the rock (granite), which leads to entrainment of the most resistant solid phases (intact or partially molten minerals) into the melt. Minerals more resistant to melting, such as quartz and oxides, contribute substantially to a chemical balance between the preserved granite and the fusion products generated during the meteoritic impact.

Terra Nova, 23, 225–231, 2011 Abstract Biotite is an abundant hydrous silicate in the Earth’s crust and plays a critical role in the formation of felsic magmas via incongruent melting. Although biotite incongruent melting reactions have been described for various contact and regional metamorphic environments, the effects of impact‐induced melting of biotite remain poorly understood. Our observations from the 40‐km‐wide Araguainha impact structure indicate that biotite can undergo incongruent melting during impact processes, producing aluminous melts that can accumulate as pockets or fracture networks in crystalline target rocks. We observed that as much as 9% of the crystalline target at Araguainha is a crystallization product after biotite breakdown. Given the relatively low shock pressures recorded in the Araguainha central uplift (20–25 GPa), our results imply that impacts in the size of Araguainha or larger are capable of generating substantial volumes of incongruent aluminous melts in crystalline crust underlying large (>40 km diameter) impact structures.