scholarly journals Trace-Element and Pb Isotope Evidence on Extracting Sulfides from Potassic Melts beneath Longmenshan and Molabushan Volcanoes, Wudalianchi, Northeast China

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 319 ◽  
Author(s):  
Sergei Rasskazov ◽  
Yi-Min Sun ◽  
Irina Chuvashova ◽  
Tatyana Yasnygina ◽  
Chen Yang ◽  
...  
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Volcanic Field ◽  
Lava Flows ◽  
Pb Isotope ◽  
Linear Pattern ◽  
Wide Range ◽  
Mantle Sources ◽  
Isotope Evidence ◽  
Isotope Study

In the Wudalianchi volcanic field, eruptions started with low-Mg potassic lava flows 2.5–2.0 Ma ago and later changed to both low- and moderate-Mg potassic compositions. Volcanic rocks from the Molabushan and Longmenshan volcanoes record an unusually wide range of Pb abundances (from 3.7 ppm to 21 ppm relative to predominant range of 10–15 ppm). To determine the cause of these, we performed a comparative trace-element and Pb isotope study of rocks from these volcanoes and older lava flows. On a uranogenic lead diagram, older low-Mg lavas from lithospheric mantle sources plot on a secondary isochron with a slope corresponding to an age of 1.88 Ga. This contrasts with moderate-Mg volcanic rocks from the Molabushan cone, interpreted to have been derived from a recent convective mantle source, which define a flat linear pattern. Low-Mg rocks from the Molabushan flow have lead isotopic compositions that indicate mixed Gelaqiu and Molabu sources. Relative to rocks from the Molabushan cone, moderate-Mg lavas and slags from the East Longmenshan volcano have modified compositions characterized by Pb, S, and Ni abundances, Ni/Co, Ni/MgO ratios as well as 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, Ce/Pb, Th/Pb, and U/Pb ratios. We infer that the older Wudalianchi magmas were likely derived from a Paleoproterozoic lithospheric fragment, related to the evolved primordial mantle, and that later magmas were generated in the convecting mantle. These were influenced by segregation of small amounts of sulfides.

The geochemical consequences of mixing melts from contrast sources beneath the Jiaodebushan and Xiaogushan volcanoes, Wudalianchi volcanic field, Northeast China

2021 ◽  
Author(s):  
Tatiana Yasnygina ◽  
Yi-min Sun ◽  
Sergei Rasskazov ◽  
Irina Chuvashova ◽  
Chen Yang ◽  
...  
Keyword(s):  
Northeast China ◽  
Lead Isotope ◽  
Component Composition ◽  
Volcanic Field ◽  
Lava Flows ◽  
Pb Isotope ◽  
Partial Similarity ◽  
Isotope Evidence ◽  
Derivatives Of ◽  
Potassic Rocks

<p>Potassic rocks from the Wudalianchi field are considered by some authors as derivatives of the mantle transition layer. However, this opinion is contradicted by the contrasting component composition of melts erupted in different volcanoes. From data of lead isotope compositions, the initial eruptions of lava flows 2.5–2.0 Ma ago were derived from the lithospheric Laoshantou and Gelaqiu model sources of about 1.88 Ga, while subsequent eruptions were derived from the Wohu source of about 0.15 Ga and the recent Molabu source (Rasskazov et al., 2020). Detailed sampling of volcanoes yielded geochemical evidence on both the individualization of sources beneath volcanoes and mixing of melts from contrasting sources. We present evidence on mixing of melts from the Gelaqiu, Wuhu, and Molabu sources beneath the Jiaodebushan Volcano and partial similarity of rock components from this volcano to material erupted in the Xiaogushan Volcano.</p><p>This work is supported by the RSF grant 18-77-10027.</p><p>Rasskazov S., Sun Y-M., Chuvashova I., Yasnygina T., Yang C., Xie Z., Saranina E., Gerasimov N., Vladimirova T. Trace-element and Pb isotope evidence on extracting sulfides from potassic melts beneath Longmenshan and Molabushan volcanoes, Wudalianchi, Northeast China. Minerals. 2020. V. 10: 319; doi:10.3390/min10040319</p>

Isotope evidence for the origin of Andean granites

1988 ◽  
Vol 79 (2-3) ◽  
pp. 123-133 ◽  
Author(s):  
R. J. Pankhurst ◽  
M. J. Hole ◽  
M. Brook
Keyword(s):  
Antarctic Peninsula ◽  
Nd Isotope ◽  
Depleted Mantle ◽  
Wide Range ◽  
Mantle Sources ◽  
Subducted Oceanic Crust ◽  
Isotope Evidence ◽  
The Antarctic ◽  
Isotope Systematics ◽  
Material Input

ABSTRACTThe genesis of subduction-related magmas in the Andean region of South America and the Antarctic Peninsula is considered in relation to the Palaeozoic to Cenozoic granitoids belts which are thought to parallel palaeo-coastlines. Their Sr-Nd isotope systematics show a wide range of initial compositions (87Sr/86Sr0 0·7038 to >0·710; εNd, +4 to –10) requiring material input from both depleted mantle and continental crust. In local transects there are consistent trends with time of emplacement, from enriched (crustal) to depleted (mantle) sources, regardless of the sense of migration of magmatism (towards or away from the continent). These trends represent mixing between mantle-derived material and anatectic melts of the lower crust: in each case the crustal end-member reflects the age and isotopic composition of the local deep crustal basement (Precambrian in the easternmost Andes, Palaeozoic in the W and in the Antarctic Peninsula). The depleted end-member could be derived by melting within the subducted oceanic crust, the overlying mantle or previously crystallised mafic underplating. One of the most important factors controlling the mixing process is the angle of subduction, resulting in magma generation under variable tectonic conditions.

scholarly journals Major, trace element and Sr-isotope characterization of the Samothraki tertiary volcanic rocks, NE Aegean

2001 ◽  
Vol 34 (3) ◽  
pp. 995 ◽  
Author(s):  
M. VLAHOU ◽  
G. CHRISTOFIDES ◽  
G. ELEFTHERIADIS ◽  
L. PINARELLI ◽  
A. KASSOLI-FOURNARAKI
Keyword(s):  
Trace Element ◽  
Volcanic Rocks ◽  
Sr Isotope ◽  
Rock Series ◽  
Complex Processes ◽  
Enriched Mantle ◽  
Wide Range ◽  
Volcanic Rock Series ◽  
Young Volcanic Rock

Tertiary volcanic rocks of the Samothraki Island were found to show a wide range of composition. Two series have been distinguished showing diverging trends both in major and in trace element diagrams. Sr-isotope data show even more pronounced grouping of the two series thus reinforcing the suggestion of diverse evolutionary processes. A possible origin from either an enriched mantle source for the old volcanic series and mantle plus crust for the young volcanic rock series is suggested. Fractional crystallization or any other closed system process cannot account for the geochemical and isotopie variations seen witin the rock series. More complex processes must be responsible for their evolution history.

The mineral chemistry and petrology of Tertiary pitchstones from Scotland

1998 ◽  
Vol 89 (2) ◽  
pp. 95-111 ◽  
Author(s):  
R. J. Preston ◽  
M. J. Hole ◽  
J. Still ◽  
H. Patton
Keyword(s):  
Trace Element ◽  
Major Element ◽  
Crustal Contamination ◽  
Mineral Chemistry ◽  
Lava Flows ◽  
Residual Glass ◽  
Pb Isotope ◽  
Isotope Data ◽  
Igneous Province ◽  
Basaltic Magmas

AbstractSub-silicic to silicic pitchstones are widespread throughout the British Tertiary Igneous Province (BTIP), with examples being found at all the major igneous centres. Both highly porphyritic and almost completely aphyric varieties occur, and take the form of sills, dykes and lava flows. Here we present previously unreported mineral chemistry data on phenocryst and microcrystallite populations from a number of pitchstones from throughout the BTIP. Phenocryst assemblages are completely anhydrous, comprising mixtures of plagioclase, sanidine, fayalite, orthopyroxene, pigeonite, ferroaugite, ferrohedenbergite and quartz. Microcrystallite assemblages are also diverse, consisting of sanidine, ferrohedenbergite, fayalite and, occasionally, almost pure end-member ferrosilite, as well as hydrous phases such as ferrohornblende and biotite. Textural and mineral chemistry observations support interpretations derived from whole-rock and residual glass major element analyses, together with whole-rock trace element and the available Sr-Nd-Pb isotope data, that the Tertiary pitchstones of Scotland are either the products of intimate mixing between a range of basaltic magmas with hydrous crustal melts, or were formed by the crustal contamination of basaltic magmas.

scholarly journals Anatectic origin of mid-Proterozoic granite dyke in the Isukasia area, West Greenland Pb-Pb and Rb-Sr isotope evidence

1983 ◽  
Vol 115 ◽  
pp. 38-42
Author(s):  
F Kalsbeek ◽  
P.N Taylor
Keyword(s):  
Sr Isotope ◽  
Pb Isotope ◽  
West Greenland ◽  
Fine Grained ◽  
Isotope Evidence ◽  
Isotope Study

It was found some time ago on the evidence of mineral-isotope relations that the early Archaean gneisses of the Godthåbsfjord region in West Greenland were mildly reheated during the mid-Proterozoic at c. 1600-1700 Ma (Pankhurst et al., 1973; Baadsgaard et al., 1976). A Rb-Sr whole-rock isotope study of a fine-grained granitic dyke from the Isukasia area indicated that this dyke was formed 1610 ± 130 Ma ago by anatexis of early Archaean rocks (Kalsbeek et al., 1980). This suggested that temperatures not less than c. 650°C were reached at depth, at least locally, within the Archaean craton during the Proterozoic. We have made a Pb-Pb isotope study of this dyke to check and amplify this conclusion. The field relations, petrology and chemistry of the dyke have been described in the earlier paper.

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