Geochemical variations in Andean basaltic and silicic lavas from the Villarrica-Lanin volcanic chain (39.5� S): an evaluation of source heterogeneity, fractional crystallization and crustal assimilation

1989 ◽  
Vol 103 (3) ◽  
pp. 361-386 ◽  
Author(s):  
Rosemary Hickey -Vargas ◽  
Hugo Moreno Roa ◽  
Leopolde Lopez Escobar ◽  
Frederick A. Frey
Keyword(s):  
Fractional Crystallization ◽  
Crustal Assimilation ◽  
Volcanic Chain ◽  
Geochemical Variations ◽  
Source Heterogeneity

Possible crustal contamination of Midcontinent Rift igneous rocks: examples from the Mineral Lake intrusions, Wisconsin

1992 ◽  
Vol 29 (6) ◽  
pp. 1140-1153 ◽  
Author(s):  
Karl E. Seifert ◽  
Zell E. Peterman ◽  
Scott E. Thieben
Keyword(s):  
Fractional Crystallization ◽  
Crustal Contamination ◽  
Flood Basalt ◽  
Igneous Rocks ◽  
Midcontinent Rift ◽  
Mafic Intrusions ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
Geochemical Variations ◽  
Compositional Pattern

Interlayered mafic–telsic intrusions from the Mineral Lake intrusive complex in northwest Wisconsin reflect the typical bimodal basalt–rhyolite compositional pattern of the Midcontinent Rift flood basalt province in the Lake Superior region. The later felsic intrusions were emplaced between the mafic intrusions and overlying basalt flows, and postemplacement fractional crystallization produced gradational mineralogical and geochemical variations. Isotopic and trace-element data for the Mineral Lake intrusions are consistent with mantle sources for both mafic and felsic intrusions, with compositional differences explained by the extent of fractional crystallization and crustal contamination or mantle source characteristics.εNd–εSr plots of analyzed Midcontinent Rift igneous rocks define three largely separate isotopic fields that suggest separate sources. However, the spread in isotopic data and a spider diagram plot of mafic samples from the εNd = εSr = 0 field suggest a crustal component and derivation from depleted rather than chondritic mantle. Evolved felsic rocks plotting in two negative εNd – positive εSr fields can be explained by derivation from separate enriched mantle sources or crustal contamination or both.

scholarly journals Geochemical behaviour of trace elements during fractional crystallization and crustal assimilation of the felsic alkaline magmas of the state of Rio de Janeiro, Brazil

2015 ◽  
Vol 87 (4) ◽  
pp. 1959-1979 ◽  
Author(s):  
AKIHISA MOTOKI ◽  
SUSANNA E. SICHEL ◽  
THAIS VARGAS ◽  
DEAN P. MELO ◽  
KENJI F. MOTOKI
Keyword(s):  
Trace Elements ◽  
Continental Crust ◽  
Fractional Crystallization ◽  
Rio De Janeiro ◽  
Nepheline Syenite ◽  
The State ◽  
Granitic Rocks ◽  
Alkaline Basalt ◽  
Crustal Assimilation ◽  
Geochemical Behaviour

ABSTRACT This paper presents geochemical behaviour of trace elements of the felsic alkaline rocks of the state of Rio de Janeiro, Brazil, with special attention of fractional crystallization and continental crust assimilation. Fractionation of leucite and K-feldspar increases Rb/K and decreases K2O/(K2O+Na2O). Primitive nepheline syenite magmas have low Zr/TiO2, Sr, and Ba. On the Nb/Y vs. Zr/TiO2 diagram, these rocks are projected on the field of alkaline basalt, basanite, and nephelinite, instead of phonolite. Well-fractionated peralkaline nepheline syenite has high Zr/TiO2 but there are no zircon. The diagrams of silica saturation index (SSI) distinguish the trends originated form fractional crystallization and crustal assimilation. In the field of SSI<-200, Zr/TiO2 and Ba/Sr have negative correlations to SSI in consequence of fractional crystallization. In the field of SSI>-200, they show positive correlations due to continental crust assimilation. Total REEs (Rare Earth Elements) is nearly 10 times that of granitic rocks, but LaN/SmN and LaN/YbN are similar. REE trend is linear and Eu anomaly is irrelevant. The pegmatitic liquid generated by country rock partial melting is SiO2-oversaturated and peraluminous with high Ba, Sr, Ba/Sr, Zr/TiO2, and SSI, with high content of fluids. This model justifies the peraluminous and SiO2-oversaturated composition of the rocks with relevant effects of continental crust assimilation.

Geochemistry of late Caledonian minettes from Northern Britain: implications for the Caledonian sub-continental lithospheric mantle

1996 ◽  
Vol 60 (398) ◽  
pp. 221-236 ◽  
Author(s):  
Jason C. Canning ◽  
P. J. Henney ◽  
M. A. Morrison ◽  
J. W. Gaskarth
Keyword(s):  
Trace Elements ◽  
Partial Melting ◽  
Fractional Crystallization ◽  
Lithospheric Mantle ◽  
Sr Isotope ◽  
Crustal Assimilation ◽  
Continental Lithospheric Mantle ◽  
Compositional Changes ◽  
Tectonic Dislocations

AbstractThe geochemistry of late Caledonian minettes from across the orogenic belt is compared in order to constrain the composition of the Caledonian sub-continental lithospheric mantle (SCLM). All the minettes are similar petrographically and chemically and several samples have characteristics typical of near primary mantle melts. Samples from the Northern Highlands and the Caledonian foreland show enrichment in many trace elements (notably LILE and LREE) relative to those from the Grampians, the Southern Uplands and northern England, coupled with distinct Nd and Sr isotope characteristics. Processes such as fractional crystallization, crustal assimilation, and partial melting played a negligible role in creating the differences between the two groups which reflect long-term, time-integrated differences in the compositions of their SCLM sources. The Great Glen Fault appears to represent the boundary between these two lithospheric mantle domains. Other currently exposed Caledonian tectonic dislocations cannot be correlated directly with compositional changes within the SCLM. The chemical provinciality displayed by the minettes shows some resemblance to that within other late Caledonian igneous suites, including the newer granites, suggesting that the minettes may represent the lithospheric mantle contributions to these rocks.

scholarly journals Mineral Chemistry, S-Pb-O Isotopes, and S/Se Ratios of the Niubiziliang Ni-(Cu) Sulfide Deposit in North Qaidam Orogenic Belt, NW China: Constraints on the Parental Magma Composition, Evolution, and Sulfur Saturation Mechanism

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 837
Author(s):  
Liang Li ◽  
Fengyue Sun ◽  
Huiwen Liu ◽  
Shucheng Tan ◽  
Lu Yu ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Parental Magma ◽  
Mineral Chemistry ◽  
Orogenic Belt ◽  
Sulfide Deposit ◽  
Crustal Assimilation ◽  
Nw China ◽  
O Isotopes ◽  
Sulfur Saturation ◽  
North Qaidam

The Niubiziliang Ni-(Cu) deposit is the first magmatic Ni-Cu sulfide deposit in the North Qaidam Orogenic Belt (NQOB), NW China, and plays a significant role in geological evolution, Ni-Cu mineralization, and exploration in the NQOB. Here, we report on the mineral chemistry, S-Pb-O isotopes, and S/Se ratios of the mafic-ultramafic complex, which provide insights on the parental magma, evolution, and sulfur saturation mechanism. The Niubiziliang mafic-ultramafic intrusion contains four ore blocks and about ten Ni-(Cu) ore/mineralization bodies. Olivines in Niubiziliang belong to the species of chrysolite with Fo values of 88~89, and the pyroxenes are mainly orthopyroxene (En = 79~82) and clinopyroxene (En = 44~40). The olivines and some pyroxenes likely crystallized in a magma chamber at a depth of 35.45~36.55 km at a high temperature (1289~1369 °C) and pressure (9.38~9.67 kbar), whereas the Niubiziliang complex formed at a moderate depth (8.13~8.70 km) with a temperature and pressure of 1159~1253 °C and 2.15~2.30 kbar, respectively. The parental magma was considered to be high-Mg picritic basalt with MgO and NiO contents of 14.95~16.58% and 0.053~0.068%, respectively, which indicated high-degree partial melting of the depleted mantle. The mantle-derived primary magma underwent significant fractional crystallization and crustal assimilation and contamination, which was strongly supported by S-Pb-O isotope data and S/Se ratios, resulting in sulfur saturation and sulfide immiscibility in the magma. Crustal assimilation and contamination contributed more to sulfur saturation than fractional crystallization.

scholarly journals The Rustenburg Layered Suite formed as a stack of mush with transient magma chambers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhuosen Yao ◽  
James E. Mungall ◽  
M. Christopher Jenkins
Keyword(s):  
Magma Chamber ◽  
Fractional Crystallization ◽  
Bushveld Complex ◽  
Mineral Deposits ◽  
Ultramafic Rocks ◽  
Layered Intrusions ◽  
Crustal Assimilation ◽  
Magma Chambers ◽  
Magma Chamber Processes ◽  
Lower Crustal

AbstractThe Rustenburg Layered Suite of the Bushveld Complex of South Africa is a vast layered accumulation of mafic and ultramafic rocks. It has long been regarded as a textbook result of fractional crystallization from a melt-dominated magma chamber. Here, we show that most units of the Rustenburg Layered Suite can be derived with thermodynamic models of crustal assimilation by komatiitic magma to form magmatic mushes without requiring the existence of a magma chamber. Ultramafic and mafic cumulate layers below the Upper and Upper Main Zone represent multiple crystal slurries produced by assimilation-batch crystallization in the upper and middle crust, whereas the chilled marginal rocks represent complementary supernatant liquids. Only the uppermost third formed via lower-crustal assimilation–fractional crystallization and evolved by fractional crystallization within a melt-rich pocket. Layered intrusions need not form in open magma chambers. Mineral deposits hitherto attributed to magma chamber processes might form in smaller intrusions of any geometric form, from mushy systems entirely lacking melt-dominated magma chambers.

Pleistocene magmatism in a lithospheric transition area: petrogenesis of alkaline and peralkaline lavas from the Baringo–Bogoria Basin, central Kenya Rift

2003 ◽  
Vol 40 (9) ◽  
pp. 1239-1257 ◽  
Author(s):  
Jean-Philippe Clément ◽  
Martial Caroff ◽  
Christophe Hémond ◽  
Jean-Jacques Tiercelin ◽  
Claire Bollinger ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Crustal Assimilation ◽  
Kenya Rift ◽  
Transition Area ◽  
Short Time Span ◽  
Geochemical Variations ◽  
Short Time ◽  
Central Kenya

New petrological, geochronological, and geochemical data on basalts, mugearites, peralkaline trachytes, and phonolites from the Baringo–Bogoria Basin, central Kenya Rift, are presented. K–Ar dating indicates that the volcanic rocks were emplaced between 894 ± 13 and 92 ± 5 ka. 87Sr/86Sr ranges from 0.70304 to 0.70692, 143Nd/144Nd from 0.51237 to 0.51295, 206Pb/204Pb from 18.4 to 19.8, 207Pb/204Pb from 15.46 to 15.70, and 208Pb/204Pb from 38.2 to 40.5. Despite a rather restricted sampling area and a relatively short time span ([Formula: see text]820 ka), the mineralogical and geochemical variations are not consistent with a simple cogenetic link between the lavas. The studied area is located in a transition zone between two different lithospheric domains (Tanzanian Craton and Panafrican Mobile Belt). We propose that the petrological and geochemical variations of the studied lavas are essentially linked to the nature of the underlying lithosphere. Some basaltic products underwent carbonate contamination, possibly within the crust. Trachytes and phonolites are derived from different basaltic parents through crustal assimilation coupled with fractional crystallization. One phonolite sample contains primary calcite-rich veinlets. Textural relations and geochemical evidence suggest that there is a direct cogenetic link between these carbonate and phonolite melts. The veinlets are the modal expression of a carbonate component included in all the phonolites from the Baringo–Bogoria Basin.

Sign in / Sign up

Export Citation Format

Share Document