scholarly journals The Petrogenesis of Mid-Cretaceous Continental  Intraplate Volcanism in Marlborough, New Zealand,  during the Break-up of Gondwana

2021 ◽  
Author(s):  
◽  
Alexander Joseph McCoy-West
Keyword(s):  
New Zealand ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Small Degree ◽  
Lava Flows ◽  
Dyke Swarm ◽  
Subcontinental Lithospheric Mantle ◽  
Igneous Complex ◽  
Volcanic Material

<p>The Lookout Volcanics are the remnants of an extensive sheet of mid-Cretaceous (ca. 96 Ma) continental intraplate volcanic rocks erupted just prior to the rifting of New Zealand from Gondwana. Preserved in a fault angle depression bounded by the Awatere Fault located in Marlborough, South Island, New Zealand, the volcanic rocks cover an area of ca. 50 km2 with exposed thicknesses up to 1000 m. On the basis of stratigraphic evidence the dominantly terrestrial lavas flows are inferred to have erupted from dykes of a coeval radial dyke swarm. A detailed sampling of the lava flows of the Lookout Volcanics has been undertaken with a ca. 700 m composite stratigraphic section being constructed, largely based on a continuous sequence of lava flows outcropping in Middlehurst Stream. New Rb-Sr age constraints for the Lookout Volcanics (97.6 plus or minus 3.4 Ma) and Blue Mountain Igneous Complex (97.1 plus or minus 0.7 Ma) are consistent with previous radiometric dates of plutonic complexes in the Central Marlborough Igneous Complex, and suggest a rapid accumulation of volcanic material from ca. 98-96 Ma during the initial extension of proto-New Zealand. The predominantly mafic and alkaline samples include basalt, picrobasalt, basanite, trachybasalt and basaltic trachyandesite rock types. No samples represent primary magmas with all samples having undergone fractionation (or accumulation) of olivine plus clinopyroxene plus or minus plagioclase plus or minus Fe-Ti oxides. Initial Sr-Nd-Hf-Pb isotopic variations (87Sr/86Sr = 0.7030-0.7039; 143Nd/144Nd = 0.51272-0.51264; 176Hf/177Hf = 0.28283-0.28278; 206Pb/204Pb = 20.32-18.82) reflect mixing between melts of a HIMUlike mantle component with up to 25-30% of an Early Cretaceous upper crustal component. Oxygen isotope ratios determined by laser fluorination analysis from 6 lava flows yielded delta 18O = 4.7-5.0 per thousand for olivine, 4.8-5.4 per thousand in clinopyroxene cores, 3.9-5.5 per thousand in clinopyroxene rims. Average olivine (4.8 per thousand) and clinopyroxene core (5.1 per thousand) values are 0.4-0.5 per thousand lower than those of average mantle peridotite but comparable to those of HIMU OIB, and are consistent with New Zealand intraplate magmas being generated by a low delta 18O mantle. However, oxygen isotopic disequilibrium between clinopyroxene cores and rims (Delta 18O = -1.4 to +0.3) records the overprinting of this signature by crustal processes. Negative disequilibrium between clinopyroxene rims and cores in primitive samples suggests these phenocrysts grew in a shallow crustal magma chamber with an active meteoric water system. The effects of crustal assimilation can also be observed with clinopyroxene phenocrysts from the most evolved sample exhibiting coupled elevated delta 18O and 87Sr/86Sr. Variations in incompatible trace element ratios are consistent with the Lookout Volcanics being the small degree (2-5%) partial melts of an amphibole-bearing garnet pyroxenite. Furthermore, the elevated NiO contents of olivine phenocrysts are consistent with melting of a pyroxenitic mantle source. The presence of residual amphibole constrains melting to the hydrous subcontinental lithospheric mantle. The Lookout Volcanics and coeval plutonic complexes are the oldest occurrences of HIMU magmatism in Zealandia. This source was generated by small degree silicate melts from recycled oceanic lithosphere that metasomatised the base of the subcontinental lithospheric mantle beneath East Gondwana over 200 Ma ago.</p>

scholarly journals The Petrogenesis of Mid-Cretaceous Continental  Intraplate Volcanism in Marlborough, New Zealand,  during the Break-up of Gondwana

2021 ◽  
Author(s):  
◽  
Alexander Joseph McCoy-West
Keyword(s):  
New Zealand ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Small Degree ◽  
Lava Flows ◽  
Dyke Swarm ◽  
Subcontinental Lithospheric Mantle ◽  
Igneous Complex ◽  
Volcanic Material

<p>The Lookout Volcanics are the remnants of an extensive sheet of mid-Cretaceous (ca. 96 Ma) continental intraplate volcanic rocks erupted just prior to the rifting of New Zealand from Gondwana. Preserved in a fault angle depression bounded by the Awatere Fault located in Marlborough, South Island, New Zealand, the volcanic rocks cover an area of ca. 50 km2 with exposed thicknesses up to 1000 m. On the basis of stratigraphic evidence the dominantly terrestrial lavas flows are inferred to have erupted from dykes of a coeval radial dyke swarm. A detailed sampling of the lava flows of the Lookout Volcanics has been undertaken with a ca. 700 m composite stratigraphic section being constructed, largely based on a continuous sequence of lava flows outcropping in Middlehurst Stream. New Rb-Sr age constraints for the Lookout Volcanics (97.6 plus or minus 3.4 Ma) and Blue Mountain Igneous Complex (97.1 plus or minus 0.7 Ma) are consistent with previous radiometric dates of plutonic complexes in the Central Marlborough Igneous Complex, and suggest a rapid accumulation of volcanic material from ca. 98-96 Ma during the initial extension of proto-New Zealand. The predominantly mafic and alkaline samples include basalt, picrobasalt, basanite, trachybasalt and basaltic trachyandesite rock types. No samples represent primary magmas with all samples having undergone fractionation (or accumulation) of olivine plus clinopyroxene plus or minus plagioclase plus or minus Fe-Ti oxides. Initial Sr-Nd-Hf-Pb isotopic variations (87Sr/86Sr = 0.7030-0.7039; 143Nd/144Nd = 0.51272-0.51264; 176Hf/177Hf = 0.28283-0.28278; 206Pb/204Pb = 20.32-18.82) reflect mixing between melts of a HIMUlike mantle component with up to 25-30% of an Early Cretaceous upper crustal component. Oxygen isotope ratios determined by laser fluorination analysis from 6 lava flows yielded delta 18O = 4.7-5.0 per thousand for olivine, 4.8-5.4 per thousand in clinopyroxene cores, 3.9-5.5 per thousand in clinopyroxene rims. Average olivine (4.8 per thousand) and clinopyroxene core (5.1 per thousand) values are 0.4-0.5 per thousand lower than those of average mantle peridotite but comparable to those of HIMU OIB, and are consistent with New Zealand intraplate magmas being generated by a low delta 18O mantle. However, oxygen isotopic disequilibrium between clinopyroxene cores and rims (Delta 18O = -1.4 to +0.3) records the overprinting of this signature by crustal processes. Negative disequilibrium between clinopyroxene rims and cores in primitive samples suggests these phenocrysts grew in a shallow crustal magma chamber with an active meteoric water system. The effects of crustal assimilation can also be observed with clinopyroxene phenocrysts from the most evolved sample exhibiting coupled elevated delta 18O and 87Sr/86Sr. Variations in incompatible trace element ratios are consistent with the Lookout Volcanics being the small degree (2-5%) partial melts of an amphibole-bearing garnet pyroxenite. Furthermore, the elevated NiO contents of olivine phenocrysts are consistent with melting of a pyroxenitic mantle source. The presence of residual amphibole constrains melting to the hydrous subcontinental lithospheric mantle. The Lookout Volcanics and coeval plutonic complexes are the oldest occurrences of HIMU magmatism in Zealandia. This source was generated by small degree silicate melts from recycled oceanic lithosphere that metasomatised the base of the subcontinental lithospheric mantle beneath East Gondwana over 200 Ma ago.</p>

Fe-Cu-S rich melts in the subcontinental lithospheric mantle: insight from the Lower Silesian (SW Poland) xenoliths

2020 ◽  
Author(s):  
Hubert Mazurek ◽  
Jakub Ciążela ◽  
Magdalena Matusiak-Małek ◽  
Jacek Puziewicz ◽  
Theodoros Ntaflos
Keyword(s):  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Mantle Xenoliths ◽  
Subcontinental Lithospheric Mantle ◽  
Origin And Evolution ◽  
Depleted Mantle ◽  
Group A ◽  
Sw Poland ◽  
Group B

&lt;p&gt;Migration of strategic metals through the lithospheric mantle can be tracked by sulfides in mantle xenoliths. Cenozoic mafic volcanic rocks from the SW Poland (Lower Silesia, Bohemian Massif) host a variety of subcontinental lithospheric mantle (SCLM) xenoliths. To understand metal migration in the SCLM we studied metal budget of peridotites from the Wilcza G&amp;#243;ra basanite and their metasomatic history.&lt;/p&gt;&lt;p&gt;The Wilcza G&amp;#243;ra xenoliths are especially appropriate to study metasomatic processes as they consist of 1) peridotites with Ol&lt;sub&gt;Fo=89.1-91.5 &lt;/sub&gt;representing depleted mantle (group A); 2) peridotites with Ol&lt;sub&gt;Fo=84.2-89.2&lt;/sub&gt; representing melt-metasomatized mantle (group B), as well as 3) hornblende-clinopyroxenites and websterites with Ol&lt;sub&gt;Fo=77.2-82.5&lt;/sub&gt; representing former melt&amp;#160; channels (group C; Matusiak-Ma&amp;#322;ek et al., 2017). The inherent sulfides are either interstitial or enclosed in the silicates. High-temperature exsolutions of pyrrhotite (Po), pentlandite (Pn) and chalcopyrite (Ccp) indicate magmatic origin of the sulfides.&lt;/p&gt;&lt;p&gt;The three peridotitic groups differ by sulfide mode and composition. The sulfide modes are enhanced in group C (0.022-0.963 vol.&amp;#8240;) and group B (&lt;0.028 vol. &amp;#8240;) with respect to group A (&lt;0.002 vol.&amp;#8240;). The sulfides of group C are Ni-poor and Fe-Cu-rich as reflected in their mineral composition (Po&lt;sub&gt;55-74&lt;/sub&gt;Ccp&lt;sub&gt;1-2&lt;/sub&gt;Pn&lt;sub&gt;24-44&lt;/sub&gt; in group A, Po&lt;sub&gt;67-85&lt;/sub&gt;Ccp&lt;sub&gt;1-6&lt;/sub&gt;Pn&lt;sub&gt;14-33&lt;/sub&gt;, in group B and Po&lt;sub&gt;80-97&lt;/sub&gt;Ccp&lt;sub&gt;1-7&lt;/sub&gt;Pn&lt;sub&gt;2-20 &lt;/sub&gt;in group C) and major element chemical composition. Ni/(Ni+Fe) of pentlandite is the lowest in group C (~0.25) and the highest in group A (0.54-0.61). Cu/(Cu+Fe) of chalcopyrite is 0.32-0.49 in group C contrasting to~0.50 in groups A and B.&amp;#160;&lt;/p&gt;&lt;p&gt;The sulfide-rich xenoliths of group C indicate an important role of pyroxenitic veins in transporting Fe-Cu-S-rich melts from the upper mantle to the crust. However, the moderately enhanced sulfide modes in melt-mantle reaction zones represented by xenoliths of group B demonstrate that the upper continental mantle is refertilized with these melts during their ascent. Hence, significant portion of S and metals remains in the mantle never reaching the crust, as has been previously observed in the oceanic lithosphere (Ciazela et al., 2018).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgments:&lt;/strong&gt; This study was supported by the NCN project no. UMO-2014/15/B/ST10/00095. The EPMA analyses were funded from the Polish-Austrian project WTZ PL 08/2018.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Ciazela, J., Koepke, J., Dick, H. J. B., Botcharnikov, R., Muszynski, A., Lazarov, M., Schuth, S., Pieterek, B. &amp; Kuhn, T. (2018). Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23 N, MAR). Geochimica et Cosmochimica Acta, 230, 155-189&lt;/p&gt;&lt;p&gt;Matusiak-Ma&amp;#322;ek, M., Puziewicz, J., Ntaflos, T., Gr&amp;#233;goire, M., Kuku&amp;#322;a, A. &amp; Wojtulek P.&amp;#160;&amp;#160; M. (2017). Origin and evolution of rare amphibole-bearing mantle peridotites from Wilcza G&amp;#243;ra (SW Poland), Central Europe. Lithos 286&amp;#8211;287, 302&amp;#8211;323.&lt;/p&gt;

Ultramafic mantle xenoliths in the Late Cenozoic Volcanic rocks of the Antarctic Peninsula and Jones Mountains, West Antarctica

2021 ◽  
pp. M56-2019-44
Author(s):  
Philip T. Leat ◽  
Aidan J. Ross ◽  
Sally A. Gibson
Keyword(s):  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Incompatible Trace Element ◽  
Mantle Xenoliths ◽  
South Shetland Islands ◽  
West Antarctica ◽  
Gondwana Margin

AbstractAbundant mantle-derived ultramafic xenoliths occur in Cenozoic (7.7-1.5 Ma) mafic alkaline volcanic rocks along the former active margin of West Antarctica, that extends from the northern Antarctic Peninsula to Jones Mountains. The xenoliths are restricted to post-subduction volcanic rocks that were emplaced in fore-arc or back-arc positions relative to the Mesozoic-Cenozoic Antarctic Peninsula volcanic arc. The xenoliths are spinel-bearing, include harzburgites, lherzolites, wehrlites and pyroxenites, and provide the only direct evidence of the composition of the lithospheric mantle underlying most of the margin. The harzburgites may be residues of melt extraction from the upper mantle (in a mid-ocean ridge type setting), that accreted to form oceanic lithosphere, which was then subsequently tectonically emplaced along the active Gondwana margin. An exposed highly-depleted dunite-serpentinite upper mantle complex on Gibbs Island, South Shetland Islands, supports this interpretation. In contrast, pyroxenites, wehrlites and lherzolites reflect percolation of mafic alkaline melts through the lithospheric mantle. Volatile and incompatible trace element compositions imply that these interacting melts were related to the post-subduction magmatism which hosts the xenoliths. The scattered distribution of such magmatism and the history of accretion suggest that the dominant composition of sub-Antarctic Peninsula lithospheric mantle is likely to be harzburgitic.

scholarly journals Tectonic boundaries, crustal weakness zones and plume-subcontinental lithospheric mantle interactions in the Serra do Mar dyke swarm, SE Brazil

2007 ◽  
Vol 37 (01) ◽  
pp. 194-201 ◽  
Author(s):  
Sergio de Castro Valente ◽  
Artur Corval ◽  
Beatriz Paschoal Duarte ◽  
Robert M. Ellam ◽  
Anthony E. Fallick ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Dyke Swarm ◽  
Subcontinental Lithospheric Mantle ◽  
Serra Do Mar ◽  
Se Brazil ◽  
Weakness Zones ◽  
Tectonic Boundaries

PETROPHYSICAL AND MECHANICAL PROPERTIES OF BURIED VOLCANIC ROCKS ON BANKS PENINSULA, NEW ZEALAND

2019 ◽  
Author(s):  
Juliette Saux ◽  
◽  
Brooke Carlson ◽  
Marlene C. Villeneuve ◽  
Samuel J. Hampton
Keyword(s):  
Mechanical Properties ◽  
New Zealand ◽  
Volcanic Rocks

The Peninsular Ranges Batholith: an insight into the evolution of the Cordilleran batholiths of southwestern North America

1988 ◽  
Vol 79 (2-3) ◽  
pp. 105-121 ◽  
Author(s):  
L. T. Silver ◽  
B. W. Chappell
Keyword(s):  
Baja California ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Radiometric Dating ◽  
Island Arcs ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
Basaltic Composition ◽  
Peninsular Ranges ◽  
General Aspects

ABSTRACTThe Peninsular Ranges Batholith of southern and Baja California is the largest segment of a Cretaceous magmatic arc that was once continuous from northern California to southern Baja California. In this batholith, the emplacement of igneous rocks took place during a single sequence of magmatic activity, unlike many of the other components of the Cordilleran batholiths which formed during successive separate magmatic episodes. Detailed radiometric dating has shown that it is a composite of two batholiths. A western batholith, which was more heterogeneous in composition, formed as a static magmatic arc between 140 and 105 Ma and was intrusive in part into related volcanic rocks. The eastern batholith formed as a laterally transgressing arc which moved away from those older rocks between 105 and 80 Ma, intruding metasedimentary rocks. Rocks of the batholith range from undersaturated gabbros through to felsic granites, but tonalite is the most abundant rock throughout. Perhaps better than elsewhere in the Cordillera, the batholith shows beautifully developed asymmetries in chemical and isotopic properties. The main gradients in chemical composition from W to E are found among the trace elements, with Ba, Sr, Nb and the light rare earth elements increasing by more than a factor of two, and P, Rb, Pb, Th, Zn and Ga showing smaller increases. Mg and the transition metals decrease strongly towards the E, with Sc, V and Cu falling to less than half of their value in the most westerly rocks. Oxygen becomes very systematically more enriched in18O from W to E and the Sr, Nd and Pb isotopic systems change progressively from mantle values in the W to a more evolved character on the eastern side of the batholith. In detail the petrogenesis of the Peninsular Ranges Batholith is not completely understood, but many general aspects of the origin are clear. The exposed rocks, particularly in the western batholith, closely resemble those of present day island arcs, although the most typical and average tonalitic composition is distinctly more felsic than the mean quartz diorite or mafic andesite composition of arcs. Chemical and isotopic properties of the western part of the batholith indicate that it formed as the root of a primitive island arc on oceanic lithosphere at a convergent plate margin. Further E, the plutonic rocks appear to have been derived by partial melting from deeper sources of broadly basaltic composition at subcrustal levels. The compositional systematics of the batholith do not reflect a simple mixing of various end-members but are a reflection of the differing character of the source regions laterally and vertically away from the pre-Cretaceous continental margin.

Volcanoes geological mapping and structural geology with UAS High Resolution Digital Terrain Model : the Kuei-Shan Tao case example (Eastern Taiwan).

2021 ◽  
Author(s):  
Benoit Deffontaines ◽  
Kuo-Jen Chang ◽  
Samuel Magalhaes ◽  
Gérardo Fortunato
Keyword(s):  
High Resolution ◽  
Okinawa Trough ◽  
Volcanic Rocks ◽  
Digital Terrain Model ◽  
Structural Features ◽  
Point Of View ◽  
Geological Mapping ◽  
Lava Flows ◽  
Aerial Photographs ◽  
Structural Scheme

&lt;p&gt;Volcanic areas in the World are often difficult to map especially in a structural point of view as (1) fault planes are generally covered and filled by more recent lava flows and (2) volcanic rocks have very few tectonic striations. Kuei-Shan Tao (11km from Ilan Plain &amp;#8211; NE Taiwan) is a volcanic island, located at the soutwestern tip of the South Okinawa trough (SWOT). Two incompatible geological maps had been already published both lacking faults and structural features (Hsu, 1963 and Chiu et al., 2010). We propose herein not only to up-date the Kuei-Shan Tao geological map with our high resolution dataset, but also to create the Kuei-Shan Tao structural scheme in order to better understand its geological and tectonic history.&lt;/p&gt;&lt;p&gt;Consequently, we first acquired aerial photographs from our UAS survey and get our new UAS high resolution DTM (HR UAS-DTM hereafter) with a ground resolution &lt;10cm processed through classical photogrammetric methods. Taking into account common sense geomorphic and structural interpretation and reasoning deduced form our HR UAS-DTM, and the outcropping lithologies situated all along the shoreline, we have up-dated the Kuei-Shan Tao geological mapping and its major structures. To conclude, the lithologies (andesitic lava flows and pyroclastic falls) and the new structural scheme lead us to propose a scenario for both the construction as well as the dismantling of Kuei-Shan Tao which are keys for both geology and geodynamics of the SWOT.&lt;/p&gt;

Age of the Grenville dyke swarm, Ontario–Quebec: implications for the timing of lapetan rifting

1995 ◽  
Vol 32 (3) ◽  
pp. 273-280 ◽  
Author(s):  
S. L. Kamo ◽  
T. E. Krogh ◽  
P. S. Kumarapeli
Keyword(s):  
Long Range ◽  
Volcanic Rocks ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Alkaline Complex ◽  
Southeastern Part ◽  
Time Marker ◽  
Continental Breakup ◽  
Iapetus Ocean

U–Pb baddeleyite and zircon ages for three diabase dykes from widely spaced localities within the Grenville dyke swarm indicate a single age of emplacement at [Formula: see text] Ma. The 700 km long Grenville dyke swarm, located in the southeastern part of the Canadian Shield, was emplaced syntectonically with the development of the Ottawa graben. This graben may represent a plume-generated lapetan failed arm that developed at the onset of the breakup of Laurentia. Other precisely dated lapetan rift-related units, such as the Callander Alkaline Complex and the Tibbit Hill Formation volcanic rocks, indicate a protracted 36 Ma period of rifting and magmatism prior to volcanism along this segment of the lapetan margin. The age of the Grenville dykes is the youngest in a progression of precisely dated mafic magmatic events from the 723 Ma Franklin dykes and sills to the 615 Ma Long Range dykes, along the northern and northeastern margins of Laurentia, respectively. Thus, the age for these dykes represents a key time marker for continental breakup that preceded the formation of the Iapetus ocean.

Sign in / Sign up

Export Citation Format

Share Document