The Carboniferous Baralacha La basaltic dykes (Upper Lahul, Ladakh) : remnants of an early rifting event along the Indian northern plate

2005 ◽  
Vol 176 (6) ◽  
pp. 499-511 ◽  
Author(s):  
François Chauvet ◽  
Henriette Lapierre ◽  
Delphine Bosch ◽  
Alain Demant ◽  
François Bussy ◽  
...  
Keyword(s):  
Rare Earth ◽  
Mantle Source ◽  
Incompatible Trace Element ◽  
Passive Margin ◽  
Dyke Swarm ◽  
Light Rare Earth ◽  
Pb Isotope ◽  
Alkali Basalts ◽  
Lower Carboniferous ◽  
Trace Element Contents

Abstract The Lower Carboniferous Baralacha La basaltic dykes were emplaced along transtensional faults. The basalts exhibit tholeiitic and alkaline affinities. The tholeiites are TiO2-poor, moderately enriched in light rare earth (LREE), and display Nb and Ta negative and Th positive anomalies. The alkali basalts, compared to the tholeiites, have higher TiO2, rare earth and highly incompatible trace element contents and greater LREE enrichments. The Nd and Pb isotope compositions of the Baralacha La basalts suggest that they derive from the partial melting of an enriched OIB mantle source, characterized by a HIMU component, and contaminated by the lower continental crust. The Baralacha La dyke swarm represent the remnants of an early rifting event on the northern Indian passive margin.

scholarly journals Origin of Northeast Fujian Basalts and Limitations on the Heterogeneity of Mantle Sources for Cenozoic Alkaline Magmatism across SE China: Evidence from Zircon U-Pb Dating, Petrological, Whole-Rock Geochemical, and Isotopic Studies

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 770
Author(s):  
Guishan Zhang ◽  
Ren Peng ◽  
Hongxin Qiu ◽  
Hanjie Wen ◽  
Yonggang Feng ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Mantle Source ◽  
Trace Element Geochemistry ◽  
Alkaline Magmatism ◽  
Element Geochemistry ◽  
Alkali Basalts ◽  
Mantle Sources ◽  
Heavy Rare Earth Elements ◽  
Se China

Cenozoic alkali basalts in Southeast (SE) China generally are genetically related to intracontinental rifting. Hence, they can be used to probe the nature of their underlying mantle sources and aid studies of the tectonic background in this region. This paper focuses on the Shanhoujian alkali basalts located in Bailing County, northeastern Fujian, SE China. We herein report their petrology, whole-rock major, and trace element geochemistry, and Sr-Nd isotopic composition and provide a new zircon U-Pb age for the basalts (~40 Ma, Eocene). These data help to constrain the petrogenesis of alkali basalts, their mantle source, and tectonic settings. The basalts are characterized by high Mg# (58.21–63.52) with Na2O/K2O > 1. MgO content is weakly correlated with CaO and Cr content but shows no correlation with Ni and Fe2O3 (total). Such features suggest that fractionation of clinopyroxene rather than olivine was important. In terms of trace elements, the alkali basalts display: (1) enrichment in La, Ce, Rb, Ba, Nb, and Ta and depletion in K, Pb, Zr, Hf, and Ti and (2) notable fractionation of light rare earth elements from heavy rare earth elements. Determined (87Sr/86Sr)i is in the range of 0.7041–0.7040 and εNd (t) is between +3.2 and +3.3. The Shanhoujian alkali basalts show a notable affinity to oceanic island basalts (OIBs) with little assimilation of crustal materials. They were derived from a pyroxenite and carbonated peridotite mantle source metasomatized by sediments carried by the subduction plate at different depths. The primary magmas of these basalts were derived from partial melting of this metasomatized mantle source during upwelling of the asthenospheric mantle as an intracontinental rift formed through extension in this part of SE China.

CORE-HOLE SCREENING IN LIGHT RARE-EARTH INSULATING COMPOUNDS

1986 ◽  
Vol 47 (C8) ◽  
pp. C8-961-C8-964
Author(s):  
E. BEAUREPAIRE ◽  
F. LE NORMAND ◽  
G. KRILL
Keyword(s):  
Rare Earth ◽  
Light Rare Earth ◽  
Core Hole

scholarly journals Behavior of sulfate in preparation of single light rare earth carbonate by Mg(HCO3)2 precipitation method

2021 ◽  
Author(s):  
Meng Wang ◽  
Xiaowei Huang ◽  
Zongyu Feng ◽  
Chao Xia ◽  
Deliang Meng ◽  
...  
Keyword(s):  
Rare Earth ◽  
Precipitation Method ◽  
Light Rare Earth

Interpretation of Pb isotope compositions of galenas from the Midland Valley of Scotland and adjacent regions

1984 ◽  
Vol 75 (2) ◽  
pp. 85-96 ◽  
Author(s):  
John Parnell ◽  
Ian Swainbank
Keyword(s):  
Lower Devonian ◽  
Lead Isotope ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Igneous Rocks ◽  
Pb Isotope ◽  
Lower Carboniferous ◽  
Granite Magma ◽  
Lower Palaeozoic ◽  
Caledonian Granite

ABSTRACTThe lead isotope compositions of 61 galenas from central and southern Scotland vary markedly between different regions. Most galenas from the southern Grampian Highlands yield isotope ratios (206Pb/204Pb 17·77 ± 0·25, 207Pb/204Pb 15·47 ± 0·05, 208Pb/204Pb 37·63 ± 0·26) less radiogenic than those from Midland Valley galenas (18·22 ± 0·12, 15·55 ± 0·05, 38·13 ± 0·14) whilst galena lead from the Southern Uplands (18·28 ± 0·12, 15·56 ± 0·03, 38·21 ± 0·18) is more radiogenic than that from the southern Midland Valley (18·12 ± 0·06, 15·52 ± 0·02, 38·06 ±0·10). The change in isotopie composition across the Highland Boundary fault reflects the presence or absence of Dalradian rocks which included a magmatic component of lead. Galenas from the Dalradian sequence in Islay, where igneous rocks are lacking, have a composition (18·14±0·04, 15·51±0·01, 37·90±0·02) more like Midland Valley galenas. In the Southern Uplands, galenas yield lead isotope ratios similar to those of feldspars from Caledonian granite (18·30 ± 0·14, 15·57 ± 0·04, 37·96 ± 0·15) analysed by Blaxland et al. (1979). The similar ratios reflect the incorporation of Lower Palaeozoic sedimentary rocks into the granite magma, rather than a granitic source for the mineralisation. The granites were then thermal-structural foci for later mineralising fluids which leached metals from the surrounding rocks. Within the Midland Valley, galenas hosted in Lower Devonian-Lower Carboniferous lavas are notably more radiogenic (18·31 ±0·12, 15·58 ± 0·06, 38·20 ± 0·16) than sediment-hosted galenas (18·14 ± 0·07, 15·52 ± 0·02, 38·08 ± 0·10). The Devonian lavas at least may have inherited lead from subducted (? Lower Palaeozoic) rock incorporated in the primary magma.

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