Stable isotope compositions and water contents of boninite series volcanic rocks from Chichi-jima, Bonin Islands, Japan

1987 ◽  
Vol 82 (1-2) ◽  
pp. 75-86 ◽  
Author(s):  
Patrick F. Dobson ◽  
James R. O'Neil
Keyword(s):  
Stable Isotope ◽  
Volcanic Rocks ◽  
Bonin Islands ◽  
Water Contents

New FTIR data of calc-alkaline volcanic rocks from the Oas-Gutai Mts. and post eruption effects on the water content of phenocrysts

2020 ◽  
Author(s):  
Ákos Kővágó ◽  
Marinel Kovacs ◽  
Dóra Kesjár ◽  
Csaba Szabó ◽  
István Kovács
Keyword(s):  
Water Content ◽  
Volcanic Rocks ◽  
Parental Magma ◽  
Volcanic Eruptions ◽  
Ftir Spectra ◽  
Future Research ◽  
Calc Alkaline ◽  
Structural Hydroxyl ◽  
Volcanic Facies ◽  
Water Contents

<p>We studied volcanic rocks from the Oas-Gutai Mts. (Transylvania, Romania) to measure the ‘structural hydroxyl’ content of the nominally anhydrous minerals (NAMs such as clinopyroxene, plagioclase, quartz), from which water content of the parental magma can be estimated.  The Neogene volcanic chain of the Carpathian-Pannonian region (CPR), due to petrologic variability, is an excellent area for such investigation.</p><p>Recent FTIR studies on the calc-alkaline rocks from CPR, showed that the ‘structural hydroxyl’ content of NAMs could be modified during and after volcanic eruptions [1], [2], [3]. However, transmission FTIR-microscopy is an adequate technique for recognizing this these changes because FTIR spectra of the NAMs indicate signs in the case of hydroxyl loss [4].</p><p>For studying the pre-eruptive water contents clinopyroxenes are the most promising mineral because it has one of the lowest diffusion rates for hydroxyl in NAMs [5]. With the detailed study of the clinopyroxenes FTIR spectra, conclusions can be drawn concerning the potential post-eruptive loss of hydroxyl [4].</p><p>We have examined 8 volcanic rock samples, four dacite samples from Oas and one basalt two andesite and one rhyolite sample from the Gutai Mts. The samples show diverse volcanic facies such as lava, ignimbrite and debris avalanche. The diversity of samples is important for future research because it will help to choose the most adequate volcanic facies to estimate the magmatic equilibrium water contents.</p><p>The studied clinopyroxenes contain 83-371 ppm ‘structural hydroxyl’ content,which can be considered as normal values compared to the work of [6] where ‘structural hydroxyl’ content in clinopyroxenes show a range from 75 to 390 ppm in the mafic calc-alkaline lavas from Salina, Italy.</p><p>[1] Lloyd, A.S., Ferriss, E., Ruprecht, P., Hauri, E.H., Jicha, B.R., & Plank, T. (2016): Journal of Petrology, 57, pp. 1865-1886</p><p>[2] Biró, T., I. Kovács, D. Karátson, R. Stalder, E. Király, G. Falus, T. Fancsik, J. & Sándorné Kovács (2017): American Mineralogist, 102, pp.</p><p>[3] Pálos, Z., Kovács, I. J., Karátson, D., Biró, T., Sándorné Kovács, J., Bertalan, É., & Wesztergom, V. (2019): Central European Geology, 62(1)</p><p>[4] Patkó, L., Liptai, N., Kovács, I., Aradi, L., Xia, Q.K., Ingrin, J., Mihály, J., O'Reilly, S.Y., Griffin, W.L., Wesztergom, V., & Szabó, C. (2019): Chemical Geology, 507, pp. 23-41.</p><p>[5] Farver, J.R. (2010): Reviews in Mineralogy and Geochemistry, 72 (1), pp. 447–507.</p><p>[6] Nazzareni, S., Skogby H., & Zanazzi, P.F. (2011): Contributions to Mineralogy and Petrology, 162, pp. 275–288.</p>

scholarly journals Geochemical Evolution of Arc and Slab Following Subduction Initiation: a Record from the Bonin Islands, Japan

2020 ◽  
Vol 61 (5) ◽  
Author(s):  
Osamu Ishizuka ◽  
Rex N Taylor ◽  
Susumu Umino ◽  
Kyoko Kanayama
Keyword(s):  
Volcanic Rocks ◽  
Leading Edge ◽  
Geochemical Evolution ◽  
Pelagic Sediment ◽  
Bonin Islands ◽  
Stratigraphic Framework ◽  
Pacific Margin ◽  
Volcaniclastic Rocks ◽  
Mariana Arc ◽  
Ocean Ridge

Abstract Volcanism following the initiation of subduction is vital to our understanding of this specific magma-generation environment. This setting is represented by the first development of the Izu–Bonin–Mariana arc system as subduction commenced along the Western Pacific margin in the Eocene. A new collection of volcanic rocks recovered from the islands and exposed crustal sections of the Bonin Ridge spans the first 10 Myr of arc evolution. An elemental and radiogenic isotope dataset from this material is presented in conjuction with new 40Ar/39Ar ages and a stratigraphic framework developed by a detailed mapping campaign through the volcanic sections of the Bonin Islands. The dating results reveal that both the locus and type of magmatism systematically changed with time in response to the progressive sinking of the slab until the establishment of steady-state subduction at around 7–8 Ma. Following initial mid-ocean ridge basalt (MORB)-like spreading-related basalt magmatism, volcanic centres migrated away from the trench and changed from high-Si boninite to low-Si boninite or high-Mg andesite, then finally tholeiitic or calcalkaline arc magma. Subducting pelagic sediment combined with Pacific-type igneous ocean crust dominates the slab input to the shallow source of high-Si boninites at 49 Ma, but high-precision Pb isotope data show that this sediment varies in composition along the subducting plate. At around 45 Ma, volcanism switched to low-Si boninite and the pelagic sediment signature was almost entirely replaced by volcanic or volcaniclastic material originating from a HIMU ocean island source. These low-Si boninites are isotopically consistent with a slab component comprising variable proportions of HIMU volcaniclastic rocks and Pacific MORB. In turn, this signature was replaced by a Pacific MORB-dominated flux in the post 45 Ma tholeiite and calcalkaline volcanic rocks. Notably, each change in slab-derived flux coincided with a change in the magma type. Fluctuations in the slab-derived geochemical signature were superimposed on a change in the mantle wedge source from highly depleted harzburgite to a depleted MORB-type mantle-type source. In turn, this may correspond to the increasing depth of the leading edge of the slab through this 5 Myr period.

scholarly journals Petrology and Geochemistry of Boninite-Series Volcanic Rocks, Chichi-Jima, Bonin Islands, Japan

2006 ◽  
Vol 48 (8) ◽  
pp. 669-701 ◽  
Author(s):  
P. F. Dobson ◽  
J. G. Blank ◽  
S. Maruyama ◽  
J. G. Liou
Keyword(s):  
Volcanic Rocks ◽  
Bonin Islands ◽  
Petrology And Geochemistry

The palaeoenvironment of East Kirkton, West Lothian, Scotland: stable isotope evidence from silicates and sulphides

1993 ◽  
Vol 84 (3-4) ◽  
pp. 223-237 ◽  
Author(s):  
R. A. R. McGill ◽  
A. J. Hall ◽  
A. E. Fallick ◽  
A. J. Boyce
Keyword(s):  
Stable Isotope ◽  
Meteoric Water ◽  
Hot Spring ◽  
Bound Water ◽  
Strong Component ◽  
Lower Carboniferous ◽  
Isotope Evidence ◽  
Pyrite Formation ◽  
Strong Mode ◽  
Water Contents

ABSTRACTStable isotope data from the East Kirkton succession are used to elucidate the extent of hot-spring influence in the palaeoenvironment by constraining conditions of deposition of the silica and the formation of sulphides.Petrographically silica occurs as chert laminae thought to be primary, and as patchy chert considered as replacive. No evidence for biogenic silica was observed. For 20 silica samples δ18O was measured for structural oxygen and δD for bound water. δ18O(SMOW) varied between +21 and +27‰ with no sample groupings related to petrography. The range in δD(SMOW) was from −50 to −90‰ with lower values characterising replacive or altered silica; water contents of both petrographic groups were similar. A plot of δ18O versus δD for the laminated primary silica defines a grouping about the line defined by Scottish agates (Fallick et al. 1985). This suggests for the unaltered silica a formation temperature of about 60°C and a fluid containing a strong component of meteoric water. The data imply a Lower Carboniferous meteoric water δ18O composition of −3‰ and δD of −15‰, consistent with the known palaeolatitude.The only sulphide observed was pyrite; 34 samples were selected from a wide variety of lithological and textural occurrences. δ34S(CDT) ranges widely and continuously between +8 and −34‰ with no strong mode. The sulphur appears to be derived from several sources, and pyrite formation from a variety of conditions as indicated by such wide ranging data, but for the samples with the lowest δ34S the involvement of bacteria in sulphate reduction is inferred.

Genesis of bentonites from Cabo de Gata, Almeria, Spain: a stable isotope study

Clay Minerals ◽  
1983 ◽  
Vol 18 (3) ◽  
pp. 227-238 ◽  
Author(s):  
G. Leone ◽  
E. Reyes ◽  
G. Cortecci ◽  
A. Pochini ◽  
J. Linares
Keyword(s):  
Stable Isotope ◽  
Low Temperature ◽  
Volcanic Rocks ◽  
Isotopic Ratios ◽  
Normal Surface ◽  
Surface Conditions ◽  
Stable Isotopic ◽  
Isotope Study ◽  
Stable Isotope Study

AbstractOxygen (18O/16O) and hydrogen (2H/1H) isotopic ratios were measured on 22 smectite separates from bentonite deposits of the Sierra de Gata and Serrata de Nijar, Almeria, Spain. In addition, 18O/16O and 2H/1H ratios were determined on some waters from springs and wells, and 18O/16O ratios were measured on quartz, plagioclase and biotite samples separated from the bentonites. The smectites displayed two distinct isotopic compositional groups which excluded an origin either by submarine alteration or weathering under normal surface conditions of the associated volcanic rocks. Bentonization processes caused by low-temperature fluids of meteoric origin could account for the stable isotopic contents. Argillization temperatures are estimated at ∼40°C and ∼70°C for the Serrata de Nijar and the Sierra de Gata deposits, respectively.

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