title: An assessment of the mantle and slab components in the magmas of an oceanic arc volcano: Raoul Volcano, Kermadec arc

authors: Smith, Ian E.M.

subjects: Kermadec arc

abstract: Raoul Volcano occupies a simple oceanic subduction setting in the northern part of the Kermadec arc on the Pacific–Australian convergent plate boundary. The primary inputs to the magmatic system that feeds the volcano are a subduction component derived from the subducting old Pacific oceanic lithosphere and its veneer of pelagic sediment, and the overlying peridotitic mantle wedge. Conservative trace elements that are very incompatible during mantle melting are relatively depleted in Raoul lavas indicating a source that has been depleted during an earlier melting event. Major element co-variations indicate magma genesis by 25% near fractional melting of a mantle source that is weakly depleted (2% melt extraction) relative to a fertile MORB source. An important influence on the composition of the mantle component is progressive melt extraction coupled with minimal advection of fresh material into the sub-arc zone followed by melt extraction from a melting column beneath the spreading centre of an adjacent back arc basin. High field strength element and rare earth element systematics indicate involvement of a subduction-related component of constant composition. Two fluid components can be distinguished, one enriched in large ion lithophile elements inferred to be an aqueous fluid that is continuously added to the ascending melt column and the other a less mobile fluid that transfers Th. A homogeneous subduction-related component of constant composition and magnitude arises if the slab-derived flux migrates from the slab–mantle interface to the sub-arc melting column by repeated episodes of amphibole formation and decomposition its composition is then governed by the distribution coefficients of pyroxene and its magnitude by the degree of amphibole saturation of mantle peridotite. The results from Raoul Volcano are comparable to those from other oceanic subduction-related arcs such as South Sandwich and Marianas suggesting that this is a general model for oceanic arcs.

text: An assessment of the mantle and slab components in the magmas of an oceanic arc volcano: Raoul Volcano, Kermadec arc Raoul Volcano occupies a simple oceanic subduction setting in the northern part of the Kermadec arc on the Pacific–Australian convergent plate boundary. The primary inputs to the magmatic system that feeds the volcano are a subduction component derived from the subducting old Pacific oceanic lithosphere and its veneer of pelagic sediment, and the overlying peridotitic mantle wedge. Conservative trace elements that are very incompatible during mantle melting are relatively depleted in Raoul lavas indicating a source that has been depleted during an earlier melting event. Major element co-variations indicate magma genesis by 25% near fractional melting of a mantle source that is weakly depleted (2% melt extraction) relative to a fertile MORB source. An important influence on the composition of the mantle component is progressive melt extraction coupled with minimal advection of fresh material into the sub-arc zone followed by melt extraction from a melting column beneath the spreading centre of an adjacent back arc basin. High field strength element and rare earth element systematics indicate involvement of a subduction-related component of constant composition. Two fluid components can be distinguished, one enriched in large ion lithophile elements inferred to be an aqueous fluid that is continuously added to the ascending melt column and the other a less mobile fluid that transfers Th. A homogeneous subduction-related component of constant composition and magnitude arises if the slab-derived flux migrates from the slab–mantle interface to the sub-arc melting column by repeated episodes of amphibole formation and decomposition its composition is then governed by the distribution coefficients of pyroxene and its magnitude by the degree of amphibole saturation of mantle peridotite. The results from Raoul Volcano are comparable to those from other oceanic subduction-related arcs such as South Sandwich and Marianas suggesting that this is a general model for oceanic arcs.

year: 2009

title: Radical research as research at the roots: Practitioner self-image, public relations and ethics

authors: Toledano, Margalit

subjects: practitioner self-image

abstract: Semantically, radical derives from ‘radix’, the Latin for root. This paper argues that little public relations research goes back to the roots of actual practice and addresses this neglect through a project focusing on practitioner accounts of their work. When considering public relations ethics, practitioner self-images and cultural values become an essential research component. In addressing this neglected area of research, this paper examines the subjective perceptions of public relations practitioners regarding their role, commitments, and responsibilities within the framework of their specific culture and national history. In considering practitioner testimonials about professional integrity, briefs, and goals, especially as members of the society and nation to which they belong, the paper engages with ethical aspects of the practice from a cultural perspective that assumes different cultures can have different ethical expectations. In revealing the impact of features that are often ‘taken for granted’ in one country, the paper uses the example of four generations of practitioners who served one major institution in Israel to suggest how similar research at the professional roots in other nations might enable knowledge of international similarities and difference in relation to ethics in action.

text: Radical research as research at the roots: Practitioner self-image, public relations and ethics Semantically, radical derives from ‘radix’, the Latin for root. This paper argues that little public relations research goes back to the roots of actual practice and addresses this neglect through a project focusing on practitioner accounts of their work. When considering public relations ethics, practitioner self-images and cultural values become an essential research component. In addressing this neglected area of research, this paper examines the subjective perceptions of public relations practitioners regarding their role, commitments, and responsibilities within the framework of their specific culture and national history. In considering practitioner testimonials about professional integrity, briefs, and goals, especially as members of the society and nation to which they belong, the paper engages with ethical aspects of the practice from a cultural perspective that assumes different cultures can have different ethical expectations. In revealing the impact of features that are often ‘taken for granted’ in one country, the paper uses the example of four generations of practitioners who served one major institution in Israel to suggest how similar research at the professional roots in other nations might enable knowledge of international similarities and difference in relation to ethics in action.

year: 2008

title: Te Awa Tupua (Whanganui river claims settlement) Bill – the endless quest for justice

authors: Te Aho, Linda

abstract: Linda Te Aho continues her review of the new legal framework for Te Awa Tupua (the Whanganui River system) as part of the settlement of historical claims by Whanganui iwi about the Whanganui River.

text: Te Awa Tupua (Whanganui river claims settlement) Bill – the endless quest for justice Linda Te Aho continues her review of the new legal framework for Te Awa Tupua (the Whanganui River system) as part of the settlement of historical claims by Whanganui iwi about the Whanganui River.

year: 2016-08