Abstract
We present new geochemical and Nd isotopic data on two Mesoproterozoic Listvyanka (1350 ± 6 Ma) and Goloustnaya (1338 ± 3 Ma) mafic dyke swarms located in the Irkutsk Promontory of the southern part of the Siberian craton. Listvyanka dykes are sub-vertical with NNE trend, while Goloustnaya dykes are characterized by prevailing W trend. Listvyanka and Goloustnaya dykes are composed of medium to coarse grained dolerites. All dolerites correspond to sub-alkaline tholeiitic basalts according to their major-element compositions with lower to moderate mg#, varying from 36 to 54. The trace and rare earth element abundances in Listvyanka and Goloustnaya dolerites are generally close to basalts of the oceanic island basalts (OIB) type. The Listvyanka dolerites demonstrate slightly positive εNd(t) values varying from +1.1 to +1.5, while the Goloustnaya dolerites are characterized by lower εNd(t) values ranging from −0.9 to +0.1. Geochemical and isotopic affinities of the Listvyanka dolerites suggest their enrichment by a mantle plume related source. For the Goloustnaya dolerites, we assume also some additional lithospheric input to their mantle plume-related source. The emplacement of both studied dolerites took place in intracontinental extensional setting, caused by a single rising mantle plume. Listvyanka and Goloustnaya dolerites are coeval to several mafic magmatic events in northern Laurentia and likely represent part of the Mesoproterozoic plumbing system of a Siberian–Laurentian Large Igneous Province.
Highlights
The time period of 1.70–0.75 Ga is often described as the Super Gap [1,2], Boring Billion [3]or Earth’s Middle Age [4]
Minerals 2018, 8, 545 reconstruction with northern Siberia attached to western Laurentia [8,9,10], or with northern Siberia attached to northern Laurentia [11,12] have been analyzed and found to: (i) contradict Mesoproterozoic paleomagnetic data from both continents, e.g., [13,14,15,16,17]; (ii) be mostly inconsistent with Large Igneous Provinces (LIPs) records in both continents, e.g., [7,18]; (iii) contain more geological mismatches than matches, e.g., [13]
The Listvyanka dykes are sub-vertical with a NNE trend, while the Goloustnaya dykes are characterized by a prevailing W trend
Summary
The time period of 1.70–0.75 Ga is often described as the Super Gap [1,2], Boring Billion [3]or Earth’s Middle Age [4]. Minerals 2018, 8, 545 reconstruction with northern Siberia attached to western Laurentia [8,9,10], or with northern Siberia attached to northern Laurentia [11,12] have been analyzed and found to: (i) contradict Mesoproterozoic paleomagnetic data from both continents, e.g., [13,14,15,16,17]; (ii) be mostly inconsistent with LIPs records in both continents, e.g., [7,18]; (iii) contain more geological mismatches than matches, e.g., [13]. The connection between northern Siberia and western Laurentia is inconsistent with many geological and paleomagnetic lines of evidence of the connection between Australia-Antarctica with western Laurentia in Mesoproterozoic, e.g., [16,19,20,21,22,23]. It is suggested that Siberia and Laurentia were parts of the Mesoproterozoic supercontinent Columbia (aka Nuna), formed between 1.8 and
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