Mafic rocks from the Ryoke Belt, southwest Japan: implications for Cretaceous Ryoke/San-yo granitic magma genesis

2004 ◽  
Vol 95 (1-2) ◽  
pp. 249-263 ◽  
Author(s):  
Takashi Nakajima ◽  
Hiroyuki Kamiyama ◽  
Ian S. Williams ◽  
Kenichiro Tani
Keyword(s):  
Sierra Nevada ◽  
Basaltic Magma ◽  
Coarse Grained ◽  
Granitic Magma ◽  
Chemical Compositions ◽  
Southwest Japan ◽  
Mafic Rocks ◽  
Mafic Dykes ◽  
Mafic Magmas ◽  
Cretaceous Magmatism

ABSTRACTMafic rocks in the Ryoke belt, the Cretaceous granitic province in Southwest Japan, occur in two modes: (1) as mafic dykes and pillow-shaped enclaves, and (2) as isolated kilometresized bodies of gabbroic cumulate. The dykes and pillows have fine-grained textures with thin radiating plagioclase laths, indicative of quenching. The gabbroic cumulates are predominantly coarse-grained and commonly lithologically layered.SHRIMP zircon U-Pb ages of both types of mafic rocks are in the range 71–86 Ma, late Cretaceous. The mafic rocks become younger eastwards, matching the along-arc age trend of the associated Cretaceous granites (Nakajima et al. 1990). Both types of mafic rocks were apparently generated during the same magmatic event that produced the Ryoke/San-yo granites. The mafic dykes and pillows are aphyric basaltic-andesites to andesites (SiO2 54–60 wt.%), with microphenocrysts of biotite and hornblende. They have a composition which is similar to mafic rocks from the northern Sierra Nevada, and also to medium-K calc-alkaline rocks from present-day arc volcanics. The gabbroic cumulates are mostly pyroxene-hornblende gabbros (SiO2 43–52 wt.%). Their bulk-rock chemical compositions are mostly unlike any magma compositions.Both types of mafic rocks from the Ryoke belt have relatively high 87Sr/86Sr initial ratios (SrI), 0·7071–0·7097, which are similar to those of the associated granites. The granites were formed either by fractional crystallisation of the mafic magmas, or by partial melting of newly formed mafic rocks at depth. The high SrI indicates that the mafic magmas were derived from enriched mantle or mixed with enriched crustal materials. Even if the mixing occurred between primitive basaltic magma and metasedimentary rocks, then the basaltic andesite–andesite magmas must have contained more than 60% mantle-derived components. The Cretaceous magmatism in Southwest Japan represents a major episode of crustal growth by additions from the upper mantle in an arc setting.

Mafic-silicic layered intrusions: the role of basaltic injections on magmatic processes and the evolution of silicic magma chambers

1996 ◽  
Vol 87 (1-2) ◽  
pp. 233-242 ◽  
Author(s):  
R. A. Wiebe
Keyword(s):  
Basaltic Magma ◽  
Mafic Magma ◽  
Silicic Magma ◽  
Granitic Magma ◽  
Magma Chambers ◽  
Mechanical Mixing ◽  
Diffusive Convection ◽  
Type Granite ◽  
Mafic Magmas ◽  
Silicic Magmas

ABSTRACT:Plutonic complexes with interlayered mafic and silicic rocks commonly contain layers (1–50 m thick) with a chilled gabbroic base that grades upwards to dioritic or silicic cumulates. Each chilled base records the infusion of new basaltic magma into the chamber. Some layers preserve a record of double-diffusive convection with hotter, denser mafic magma beneath silicic magma. Processes of hybridisation include mechanical mixing of crystals and selective exchange of H2O, alkalis and isotopes. These effects are convected away from the boundary into the interiors of both magmas. Fractional crystallisation aad replenishment of the mafic magma can also generate intermediate magma layers highly enriched in incompatible elements.Basaltic infusions into silicic magma chambers can significantly affect the thermal and chemical character of resident granitic magmas in shallow level chambers. In one Maine pluton, they converted resident I-type granitic magma into A-type granite and, in another, they produced a low-K (trondhjemitic) magma layer beneath normal granitic magma. If comparable interactions occur at deeper crustal levels, selective thermal, chemical and isotopic exchange should probably be even more effective. Because the mafic magmas crystallise first and relatively rapidly, silicic magmas that rise away from deep composite chambers may show little direct evidence (e.g. enclaves) of their prior involvement with mafic magma.

scholarly journals Forensic igneous petrology: locating the source quarry for the “black granite" Titanic headstones in Halifax, Nova Scotia, Canada

2017 ◽  
Vol 53 ◽  
pp. 087-114
Author(s):  
D. Barrie Clarke ◽  
Christopher R.M. McFarlane ◽  
David Hamilton ◽  
David Stevens
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Coarse Grained ◽  
Chemical Compositions ◽  
Dimension Stone ◽  
Forensic Evidence ◽  
Igneous Petrology ◽  
Temporal Properties ◽  
Textural Parameters ◽  
The Right

In Halifax, Nova Scotia, 149 victims of the 1912 sinking of the Titanic lie beneath petrologically identical "black granite" headstones. Those headstones, supplied by the White Star Line, arrived in Halifax in late 1912, but no known historical document reveals their source. They consist of medium- to coarse-grained olivine-bearing gabbro, with cumulus phases consisting of randomly oriented euhedral plagioclase laths, corroded olivine, and titaniferous magnetite, and intercumulus material consisting of augite with reaction rims of hornblende, both of which are variably altered to actinolite and biotite. Three types of forensic evidence [quantitative – radiometric age of 422.1 ± 1.3 Ma (n = 17), mean olivine FeO/(FeO + MgO) values ranging from 0.43 to 0.46, augite rim trace- element compositions (35 elements), and whole-rock chemical compositions (48 elements), including statistical analysis of all these data showing no significant differences between the headstones and their putative source quarry; qualitative – mineral assemblages, modal proportions, textural parameters, style and degree of alteration; and circumstantial – regional reputation, quarrying history, local logistics, regional transportation, McGrattan marker] connect the Titanic headstones to the Saint George Batholith in southwestern New Brunswick. Precise matching of any dimension stone to its source quarry is problematic, because that material connects only to a void in the quarry. Ideally, all physical-chemical-temporal properties of the dimension stone and source quarry should match, both quantitatively and qualitatively, but in reality only the ages must almost certainly match. Thus it is remotely possible for the right quarry to mismatch most of the properties of the dimension stone, and for a wrong quarry to match most of the properties of the dimension stone. However, in the case of the Titanic headstones, the cumulative weight of all the quantitative, qualitative, and circumstantial evidence, combined with a process of elimination and application of Ockham’s razor, indicate that the Charles Hanson quarry near Bocabec, southwestern New Brunswick, is the likely source for the gabbroic Titanic headstones in Halifax, Nova Scotia.

Hydrothermal Melting of Shales

1961 ◽  
Vol 98 (1) ◽  
pp. 56-66 ◽  
Author(s):  
P. J. Wyllie ◽  
O. F. Tuttle
Keyword(s):  
Water Vapour ◽  
Basaltic Magma ◽  
Liquidus Curve ◽  
Igneous Rocks ◽  
Granitic Magma ◽  
Refractive Indices ◽  
Chemical Characteristics ◽  
Complete Fusion ◽  
Partial Fusion

AbstractPT curves for the beginning of melting of five analysed shales in the presence of water vapour under pressure are 20° C. to 40° C. higher than the corresponding curve for granite. About 150° C. above the beginning of melting, the shales are half-melted; this is higher than the liquidus curve of most granites. Refractive indices of the quenched liquids (1·495–1·505) indicate a granitic or granodioritic composition. Quartz, cordierite, mullite, hypersthene, anorthite, etc., are developed in the partially fused shales. Partial fusion of shales by a granitic magma, even if superheated, would produce a liquid no more basic than granodiorite. The chemical characteristics of the shales are compared with average igneous rocks, and there appears to be no possibility that fusion of shales could produce a basaltic magma. Complete fusion would produce a melt with composition distinct from normal igneous magmas.

Self-cannibalisation of an active cumulate system (Blumone complex, Adamello, Italy): Geochemical and experimental evidence

2020 ◽  
Author(s):  
Manuel Pimenta Silva ◽  
Peter Ulmer ◽  
Othmar Müntener
Keyword(s):  
Low Pressure ◽  
Experimental Results ◽  
Chemical Compositions ◽  
Calc Alkaline ◽  
Liquid Line ◽  
Mineral Phases ◽  
Peritectic Melting ◽  
Simple Mass ◽  
Mafic Magmas ◽  
Liquid Line Of Descent

<p>In the southern part of the Adamello Batholith (43-33 Ma; Schaltegger et al., 2019) in Northern Italy (Re di Castello superunit), we identified a multi-generational dyke suite with “exotic” chemical compositions intruding quartz-dioritic units surrounding a gabbroic complex. These dykes are characterised by SiO<sub>2</sub> contents between 43 and 46 wt.%, high Al<sub>2</sub>O<sub>3</sub> (20-21 wt.%), and low MgO and Ni (below 6.5 wt.% and 40 μg/g, respectively), displaying a nepheline-normative character. Furthermore, they exhibit positive Sr and Ba anomalies. These chemical features exclude a possible primitive character or derivation from a typical calc-alkaline liquid line of descent, as identified for the Adamello Massif (Ulmer et al, 2018). The primocrystic cargo of these dikes (clinopyroxene, anorthitic plagioclase, and low-Si, high-Na pargasitic amphibole) displays striking similarities with cumulate crystals of the contiguous Blumone amphibole gabbroic cumulate, inferring mechanical interaction of these exotic liquids with and/or derivation from the cumulate complex. Amphibole-plagioclase equilibration temperatures of the dikes (875 to 775ºC) are consistent with thermal equilibration with the surrounding quartz-dioritic mush. Sharp contacts and dyke fragmentation are also observed and are thermally congruent with the ductile-brittle transition of a quartz-dioritic to tonalitic mush (Marxer & Ulmer, 2019).</p><p>Simple mass balance calculations modelling of the peritectic melting of pargasitic amphibole and high-An plagioclase (major mineral phases of the contiguous amphibole gabbroic cumulates) with simultaneous crystallisation of low-Al clinopyroxene reveal that melt compositions similar to these dykes can be achieved with amphibole-plagioclase proportions ranging between 65:35 and 50:50. To verify if peritectic cumulate remelting represents a possible generation mechanism of these dykes we performed<span>  </span>experiments at 0.2 GPa.</p><p>Established phase equilibria of these dyke compositions reveal a lack of near-liquidus olivine, which is a rare phase in gabbroic complex. This is consistent with preliminary experimental results on cumulate melting, where olivine is also absent at high temperatures (> 1075ºC). These observations further disprove the petrogenesis of these liquids via a calc-alkaline liquid line of descent, where mafic magmas would be early saturated in olivine at low pressure further supporting their generation by local remelting of amphibole-plagioclase dominated mafic cumulates.Geochemical as well as experimental results both strongly point towards the petrogenesis of these nepheline-normative, high-Al, low-Mg picrobasalts by low pressure peritectic melting of a pargasite-anorthite cumulate assemblage in an active magmatic system.</p><p> </p><p>Marxer, F. & Ulmer, P. <em>Contrib Mineral Petr.</em> <strong>174(10)</strong>, 84 (2019).</p><p>Schaltegger, U. <em>et al. J Petrol. </em><strong>60(4)</strong>, 701-722 (2019).</p><p>Ulmer, P. <em>et al. J. Petrol.</em> <strong>59(1)</strong>, 11-58 (2018).</p>

scholarly journals The Kræmer Ø syenite, Kangerdlugssuaq: preliminary description of one of the voluminous oversaturated syenites of the East Greenland Tertiary

1991 ◽  
Vol 38 ◽  
pp. 145-151
Author(s):  
C. K. Brooks
Keyword(s):  
Main Part ◽  
Basaltic Magma ◽  
Coarse Grained ◽  
Skaergaard Intrusion ◽  
East Greenland ◽  
Partial Melt ◽  
Basaltic Melt ◽  
Basaltic Magmas ◽  
Modal Layering ◽  
Preliminary Description

Tue Kræmer Ø syenite, situated close to the Skaergaard intrusion, is typical of many oversturated syenites in the area. It consists of a maginal breccia with a sharp contact to the surrounding gneisses. This breccia, about 150 m wide is made up of basaltic clasts in a granitic matrix. It is associated with pegmatites, aplites and granophyres, all with a non-peralkaline characters. Tue main part of the syenite is a coarse-grained, massively jointed body with many large basic xenoliths and occasional modal layering. It is associated with peralkaline rhyolitic dikes and pegmatites. Anatexis of basement and crystal differentiation from a basaltic magma are thought to be unlikely processes to explain the origin of the syenites although the breccia matrix appears to be a simple partial melt of the gneisses. It is postulated thai such an anatectic melt, formed by heat transfer from basaltic magmas, becomes modified by diffusive interchange with the basaltic melt to generate the syenite in the way described for a nearby locality by Nielsen & Brooks (1988).

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