title: Combined U/Pb and (U–Th)/He geochronometry of basalt maars in Western Carpathians: implications for age of intraplate volcanism and origin of zircon metasomatism

authors: Hurai, Vratislav

subjects: Zircon

abstract: The age of intraplate volcanism in northern Pannonian Basin of Carpathians is revisited using a combination of zircon U/Pb, zircon (U–Th)/He and apatite (U–Th)/He dating techniques, complemented by electron microprobe (EMP) characterisation of dated minerals. A total of six maar structures and diatremes in the South-Slovakian Volcanic Field (SSVF) were dated and the obtained new ages yielded the following key findings: Two isolated maars in SE part indirectly dated by geomorphologic constraints to Late Pleistocene are actually of Pliocene (2.8 ± 0.2 Ma) and Late Miocene (5.5 ± 0.6 Ma) ages. In contrast, two maars in NW part of the study area are of Late Pliocene age (4.1 ± 0.4 and 5.2–5.4 Ma), younger than the Late Miocene age (~6.5 Ma) inferred previously from K/Ar data on the proximal basaltic lava flows. These maars therefore belong to the second volcanic phase that was previously identified only in SE part of the SSVF. In the light of the new geochronologic data, it seems likely that the Pliocene phreatomagmatic eruptions may have occurred along extension-related, NW- and NE-trending orthogonal faults. EMP analyses and imaging revealed an extensive syn- and post-growth metasomatic replacement by dissolution-reprecipitation in the majority of zircons. Abundant silicate melt inclusions in porous metasomatised parts of the zircons are diagnostic of magmatic rather than hydrothermal metasomatism. Consistent ages of the metasomatised and non-metasomatised zones do not indicate disturbance of the U–Pb system during the metasomatism. Enrichment in U and Th loss in the metasomatised zircons are diagnostic of an increasing oxygen fugacity triggered by degassing of the volatile residual melt during the final stages of alkali basalt fractionation. Rare zircon-to-baddeleyite transformation was probably connected with lowered silica activity in carbonated basaltic magmas in south-eastern part of the study area.

text: Combined U/Pb and (U–Th)/He geochronometry of basalt maars in Western Carpathians: implications for age of intraplate volcanism and origin of zircon metasomatism The age of intraplate volcanism in northern Pannonian Basin of Carpathians is revisited using a combination of zircon U/Pb, zircon (U–Th)/He and apatite (U–Th)/He dating techniques, complemented by electron microprobe (EMP) characterisation of dated minerals. A total of six maar structures and diatremes in the South-Slovakian Volcanic Field (SSVF) were dated and the obtained new ages yielded the following key findings: Two isolated maars in SE part indirectly dated by geomorphologic constraints to Late Pleistocene are actually of Pliocene (2.8 ± 0.2 Ma) and Late Miocene (5.5 ± 0.6 Ma) ages. In contrast, two maars in NW part of the study area are of Late Pliocene age (4.1 ± 0.4 and 5.2–5.4 Ma), younger than the Late Miocene age (~6.5 Ma) inferred previously from K/Ar data on the proximal basaltic lava flows. These maars therefore belong to the second volcanic phase that was previously identified only in SE part of the SSVF. In the light of the new geochronologic data, it seems likely that the Pliocene phreatomagmatic eruptions may have occurred along extension-related, NW- and NE-trending orthogonal faults. EMP analyses and imaging revealed an extensive syn- and post-growth metasomatic replacement by dissolution-reprecipitation in the majority of zircons. Abundant silicate melt inclusions in porous metasomatised parts of the zircons are diagnostic of magmatic rather than hydrothermal metasomatism. Consistent ages of the metasomatised and non-metasomatised zones do not indicate disturbance of the U–Pb system during the metasomatism. Enrichment in U and Th loss in the metasomatised zircons are diagnostic of an increasing oxygen fugacity triggered by degassing of the volatile residual melt during the final stages of alkali basalt fractionation. Rare zircon-to-baddeleyite transformation was probably connected with lowered silica activity in carbonated basaltic magmas in south-eastern part of the study area.

year: 2013

title: Visualize online collocation dictionary with force-directed graph

authors: Pham, Bob

subjects: Visualization

abstract: For second-language learners, collocational knowledge is very important. Knowing collocational phrases allows learners to speak and write in their targeted language naturally and reduce dramatically side effect of their first language. In order for learners to learn collocations easily, a lot of learning methods have been introduced. Particularly, learning from online-collocational corpus has become popular due to its accessibility and massive database. Although, its current presentation of information is still simple, it can be improved by using optimized representations in order to help users learning.

In this thesis, we represent a suitable way to visualize online collocational dictionary by using graph representation in order to facilitate users’ learning and provide flexible exploration. Animation is also used to increase level of engagement for users. We use force-directed model for the layout, but we develop our own graph component and combine some current algorithms in order to create a proper algorithm for our purposes. The implementation is tested by a small group of participants and the results are promising.

text: Visualize online collocation dictionary with force-directed graph For second-language learners, collocational knowledge is very important. Knowing collocational phrases allows learners to speak and write in their targeted language naturally and reduce dramatically side effect of their first language. In order for learners to learn collocations easily, a lot of learning methods have been introduced. Particularly, learning from online-collocational corpus has become popular due to its accessibility and massive database. Although, its current presentation of information is still simple, it can be improved by using optimized representations in order to help users learning.

In this thesis, we represent a suitable way to visualize online collocational dictionary by using graph representation in order to facilitate users’ learning and provide flexible exploration. Animation is also used to increase level of engagement for users. We use force-directed model for the layout, but we develop our own graph component and combine some current algorithms in order to create a proper algorithm for our purposes. The implementation is tested by a small group of participants and the results are promising.

year: 2012

title: The responsibility towards indigenous holism: Rethinking ethical research in the university

authors: Mika, Carl Te Hira

abstract: If there is one fundamental aspect of indigenous philosophy in much indigenous-related literature, it is that all things in the world are interconnected (see eg. Arola (2011); Mika (2017); Andreotti et al (2011)). The nature of this interconnection can only be speculated on (and there is undoubtedly room for more than one perspective on this). Moreover, how it could possibly take form in research, so that research is then ethical from that indigenous holistic perspective, is also at the theoretical stage, and awaits further development. In this presentation, I explore some of the exciting philosophical challenges that await the Maori theorist working in this area, including how any Maori representation about those challenges is itself constituted by all other things.

text: The responsibility towards indigenous holism: Rethinking ethical research in the university If there is one fundamental aspect of indigenous philosophy in much indigenous-related literature, it is that all things in the world are interconnected (see eg. Arola (2011); Mika (2017); Andreotti et al (2011)). The nature of this interconnection can only be speculated on (and there is undoubtedly room for more than one perspective on this). Moreover, how it could possibly take form in research, so that research is then ethical from that indigenous holistic perspective, is also at the theoretical stage, and awaits further development. In this presentation, I explore some of the exciting philosophical challenges that await the Maori theorist working in this area, including how any Maori representation about those challenges is itself constituted by all other things.

year: 2018