title: Petrogenesis of Cenozoic, alkalic volcanic lineages at Mount Morning, West Antarctica and their entrained lithospheric mantle xenoliths: Lithospheric versus asthenospheric mantle sources

authors: Martin, Adam P.

subjects: volcanic lineage

abstract: Two volcanic lineages are identified at Mount Morning, a Cenozoic to recent, eruptive centre in the Ross Sea, West Antarctica, which is part of the McMurdo Volcanic Group. Both the older (at least 18.7–11.4 Ma), mildly alkalic, nepheline- or quartz-normative Mason Spur Lineage, and the younger (at least 6–0.02 Ma), nepheline normative, strongly alkalic Riviera Ridge Lineage evolved by fractional crystallization from nominally anhydrous (<0.5 wt% H2O) parental magmas. Both lineages are analogous to other, relatively anhydrous lineages in the McMurdo Volcanic Group and distinctly different from those in which kaersutite is present on the liquid line of descent. Sub-continental lithospheric mantle (SCLM) xenoliths entrained in Riviera Ridge Lineage rocks show trace element and isotopic Sr–Nd–Pb variation that is consistent with four-component mixing whereby depleted mantle has been refertilised by enriched, HIMU-like and Nb-enriched (carbonatite) components. Refertilization may have occurred c. 530–490 Ma ago when fluids derived from subduction associated with Gondwanaland amalgamation infiltrated the SCLM. Similar trace element and isotope variation (Sr–Nd–Pb) in Mount Morning basaltic rocks and entrained xenoliths suggests that the source for the basaltic magmas lies (at least in part) in the lithospheric mantle. It has long been recognized that Cenozoic volcanic rocks in Antarctica (Victoria Land – including Mount Morning – and Marie Byrd Land), Zealandia and eastern Australia share common chemical and isotopic source characteristics and they have been argued to collectively constitute a single diffuse alkaline magmatic province (DAMP). Source characteristic similarities suggest DAMP volcanic rocks inherit at least some of their trace element and isotopic characteristics from the lithospheric mantle. Super-chondritic Nb/Ta values measured in some SCLM xenoliths and volcanic rocks at Mount Morning, and in volcanic rocks across the DAMP, can be explained by addition of ⩽5 wt% carbonatite to the source. The DAMP SCLM is a significant Nb reservoir that offers an explanation for the Nb paradox.

text: Petrogenesis of Cenozoic, alkalic volcanic lineages at Mount Morning, West Antarctica and their entrained lithospheric mantle xenoliths: Lithospheric versus asthenospheric mantle sources Two volcanic lineages are identified at Mount Morning, a Cenozoic to recent, eruptive centre in the Ross Sea, West Antarctica, which is part of the McMurdo Volcanic Group. Both the older (at least 18.7–11.4 Ma), mildly alkalic, nepheline- or quartz-normative Mason Spur Lineage, and the younger (at least 6–0.02 Ma), nepheline normative, strongly alkalic Riviera Ridge Lineage evolved by fractional crystallization from nominally anhydrous (<0.5 wt% H2O) parental magmas. Both lineages are analogous to other, relatively anhydrous lineages in the McMurdo Volcanic Group and distinctly different from those in which kaersutite is present on the liquid line of descent. Sub-continental lithospheric mantle (SCLM) xenoliths entrained in Riviera Ridge Lineage rocks show trace element and isotopic Sr–Nd–Pb variation that is consistent with four-component mixing whereby depleted mantle has been refertilised by enriched, HIMU-like and Nb-enriched (carbonatite) components. Refertilization may have occurred c. 530–490 Ma ago when fluids derived from subduction associated with Gondwanaland amalgamation infiltrated the SCLM. Similar trace element and isotope variation (Sr–Nd–Pb) in Mount Morning basaltic rocks and entrained xenoliths suggests that the source for the basaltic magmas lies (at least in part) in the lithospheric mantle. It has long been recognized that Cenozoic volcanic rocks in Antarctica (Victoria Land – including Mount Morning – and Marie Byrd Land), Zealandia and eastern Australia share common chemical and isotopic source characteristics and they have been argued to collectively constitute a single diffuse alkaline magmatic province (DAMP). Source characteristic similarities suggest DAMP volcanic rocks inherit at least some of their trace element and isotopic characteristics from the lithospheric mantle. Super-chondritic Nb/Ta values measured in some SCLM xenoliths and volcanic rocks at Mount Morning, and in volcanic rocks across the DAMP, can be explained by addition of ⩽5 wt% carbonatite to the source. The DAMP SCLM is a significant Nb reservoir that offers an explanation for the Nb paradox.

year: 2013

title: Methodology to survey and monitor New Zealand mudfish species

authors: Ling, Nicholas

subjects: Galaxiidae

abstract: Standard methods to survey and monitor NZ mudfish species involve Gee minnow traps for adults and hand nets for earlier life stages, although a range of methods have been used. A basic assessment of fish abundance can be gained from one night of trapping, however, estimates of fish density and sub-population size require repeated identical sampling events. In developing a study the objective neds to be well considered in order that the information collected addresses the particular research question. Study design and sampling effort are usually individualised to the type of habitat being sampled and resources available. Catching fish and measuring their length and weight is straightforward and uses relatively simple equipment. More detailed examination and marking of fish may be required in some studies. From information collected in the field a range of further calculations and analyses are usually done to assess the state of health of the sub-population. Capture data should be submitted to the NZ freshwater Fish Database and habitat assessed using the Handbook for Monitoring Wetland Condition. The Department of Conservation Mudfish Recovery Group plans to regularly collate survey and monitoring information.

text: Methodology to survey and monitor New Zealand mudfish species Standard methods to survey and monitor NZ mudfish species involve Gee minnow traps for adults and hand nets for earlier life stages, although a range of methods have been used. A basic assessment of fish abundance can be gained from one night of trapping, however, estimates of fish density and sub-population size require repeated identical sampling events. In developing a study the objective neds to be well considered in order that the information collected addresses the particular research question. Study design and sampling effort are usually individualised to the type of habitat being sampled and resources available. Catching fish and measuring their length and weight is straightforward and uses relatively simple equipment. More detailed examination and marking of fish may be required in some studies. From information collected in the field a range of further calculations and analyses are usually done to assess the state of health of the sub-population. Capture data should be submitted to the NZ freshwater Fish Database and habitat assessed using the Handbook for Monitoring Wetland Condition. The Department of Conservation Mudfish Recovery Group plans to regularly collate survey and monitoring information.

year: 2009

title: Sharemilking with the Te Raparahi Lands Trust (Wāotū)

authors: Hutcheson, Gail Yvonne

subjects: Place

abstract: This paper discusses sharemilking  in New Zealand.

text: Sharemilking with the Te Raparahi Lands Trust (Wāotū) This paper discusses sharemilking  in New Zealand.

year: 2017