Estimation of the radon production potential in sedimentary rocks: A case study in the Lower and Middle Jurassic of the Lusitanian Basin (Portugal)

2020 ◽  
Vol 220-221 ◽  
pp. 106272
Author(s):  
Sérgio L.R. Sêco ◽  
Filipa P. Domingos ◽  
Alcides J.S.C. Pereira ◽  
Luís V. Duarte
2004 ◽  
Vol 41 (1) ◽  
pp. 103-125 ◽  
Author(s):  
Nathan T Petersen ◽  
Paul L Smith ◽  
James K Mortensen ◽  
Robert A Creaser ◽  
Howard W Tipper

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, Sm–Nd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic – Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and Sm–Nd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.


2020 ◽  
Vol 95 ◽  
pp. 104581 ◽  
Author(s):  
Yilun Liu ◽  
Luo Liu ◽  
A-Xing Zhu ◽  
Chunhua Lao ◽  
Guohua Hu ◽  
...  

2002 ◽  
Vol 39 (9) ◽  
pp. 1313-1332 ◽  
Author(s):  
Carol A Evenchick ◽  
Vicki J McNicoll

Anyox Pendant contains complexly deformed greenschist-facies volcanic strata overlain by a thick succession of turbidite sedimentary rocks. At the contact between the two are well-studied copper-rich volcanogenic massive sulphide deposits; however the age and correlation of the volcanic strata, including the ore horizon, are poorly known. New stratigraphic, structural, and geochronology studies elucidate the regional stratigraphic, tectonic, and metallogenic settings and significance of these strata. The thick turbidite succession is correlated with Bowser Lake Group and conformably overlies the volcanic succession. Volcanogenic units include pillowed basalt, volcaniclastic rocks, chlorite phyllite, tuffaceous siltstone, and abundant gabbroic sills and dykes. Strained leucocratic intrusions yielded U–Pb zircon crystallization ages of 176.9 ± 0.2 Ma and 185.6 ± 0.3 Ma. Volcaniclastic rocks yielded detrital zircons that constrain the maximum ages of the volcanic succession. The youngest zircon grains from four samples in different structural segments limit strata to younger than ca. 186 Ma, ca. 178 Ma, ca. 183 Ma, and ca. 186 Ma. The results, combined with the regional oldest age limit of Bowser Lake Group, constrain the volcanic succession to late Early Jurassic(?) and early Middle Jurassic age, and support correlation with Hazelton Group of Stikinia. Furthermore, they enable comparisons with the coeval Au-Ag-rich stratiform Eskay Creek deposit, expanding southward the zone of extension in western Stikinia, which tapped primitive mafic magmas and accompanied the last vestiges of Stikinian volcanism in the early Middle Jurassic.


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