Lateral and Vertical Heterogeneity in the Lithospheric Mantle at the Northern Margin of the Pannonian Basin Reconstructed From Peridotite Xenolith Microstructures

A diverse suite of tholeiitic to alkaline basalt and gabbroic intrusions located in the Coldwell Complex on the northern margin of the Midcontinent Rift exhibit unusual trace element signatures that show enriched large ion lithophile elements and light rare earth elements with negative Nb and Zr anomalies. These features are not typical of magmas derived by partial melting within or above a rising mantle plume, as might be expected in an early Midcontinent Rift magmatic event. In this paper, we provide a detailed geochemical study of a 500 m thick sequence of metabasalt that represents the earliest stage of magmatism in the Coldwell Complex. We show that contamination or crystallization processes or subsequent metasomatism cannot explain the trace element variations. Instead, we propose partial melting in a metasomatized Subcontinental Lithospheric Mantle source to explain the decoupled behavior of large ion lithophile elements from light rare earth elements and heavy rare earth elements and rare earth elements from high field strength elements and the enriched Nd isotope signature of metabasalt. Similar features occur in unit 5b of the Mamainse Point Volcanic Group located at the northern margin of the Rift. An objective of this paper is to relate Two Duck Lake gabbro, host rock for low-sulfur, high precious metal sulfide mineralization at the Marathon deposit, to the metabasalt sequence. The excellent match of trace element abundances in Two Duck Lake gabbro to metabasalt unit 3 confirms an early Coldwell Complex age for metabasalt and a Subcontinental Lithospheric Mantle source for Cu – platinum group element mineralized gabbros.

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Hydrocarbon source rock potential of Miocene diatomaceous sequences in Szurdokpüspöki (Hungary) and Parisdorf/Limberg (Austria)

Austrian Journal of Earth Sciences ◽

10.17738/ajes.2020.0002 ◽

2020 ◽

Vol 113 (1) ◽

pp. 24-42

Author(s):

Emilia Tulan ◽

Michaela S. Radl ◽

Reinhard F. Sachsenhofer ◽

Gabor Tari ◽

Jakub Witkowski

Keyword(s):

Source Rock ◽

Pannonian Basin ◽

High Energy ◽

Depositional Environments ◽

Source Rocks ◽

Hydrocarbon Source Rock ◽

Petroleum Potential ◽

Northern Margin ◽

Geochemical Parameters ◽

Study Sites

AbstractDiatomaceous sediments are often prolific hydrocarbon source rocks. In the Paratethys area, diatomaceous rocks are widespread in the Oligo-Miocene strata. Diatomites from three locations, Szurdokpüspöki (Hungary) and Limberg and Parisdorf (Austria), were selected for this study, together with core materials from rocks underlying diatomites in the Limberg area. Bulk geochemical parameters (total organic carbon [TOC], carbonate and sulphur contents and hydrogen index [HI]) were determined for a total of 44 samples in order to study their petroleum potential. Additionally, 24 samples were prepared to investigate diatom assemblages.The middle Miocene diatomite from Szurdokpüspöki (Pannonian Basin) formed in a restricted basin near a volcanic silica source. The diatom-rich succession is separated by a rhyolitic tuff into a lower non-marine and an upper marine layer. An approximately 12-m thick interval in the lower part has been investigated. It contains carbonate-rich diatomaceous rocks with a fair to good oil potential (average TOC: 1.28% wt.; HI: 178 to 723 mg HC/g TOC) in its lower part and carbonate-free sediments without oil potential in its upper part (average TOC: 0.14% wt.). The composition of the well-preserved diatom flora supports a near-shore brackish environment. The studied succession is thermally immature. If mature, the carbonate-rich part of the succession may generate about 0.25 tons of hydrocarbons per square meter. The diatomaceous Limberg Member of the lower Miocene Zellerndorf Formation reflects upwelling along the northern margin of the Alpine-Carpathian Foreland. TOC contents are very low (average TOC: 0.13% wt.) and demonstrate that the Limberg Member is a very poor source rock. The same is true for the underlying and over-lying rocks of the Zellerndorf Formation (average TOC: 0.78% wt.). Diatom preservation was found to differ considerably between the study sites. The Szurdokpüspöki section is characterised by excellent diatom preservation, while the diatom valves from Parisdorf/Limberg are highly broken. One reason for this contrast could be the different depositional environments. Volcanic input is also likely to have contributed to the excellent diatom preservation in Szurdokpüspöki. In contrast, high-energy upwelling currents and wave action may have contributed to the poor diatom preservation in Parisdorf. The hydrocarbon potential of diatomaceous rocks of Oligocene (Chert Member; Western Carpathians) and Miocene ages (Groisenbach Member, Aflenz Basin; Kozakhurian sediments, Kaliakra canyon of the western Black Sea) has been studied previously. The comparison shows that diatomaceous rocks deposited in similar depositional settings may hold largely varying petroleum potential and that the petroleum potential is mainly controlled by local factors. For example, both the Kozakhurian sediments and the Limberg Member accumulated in upwelling environments but differ greatly in source rock potential. Moreover, the petroleum potential of the Szurdokpüspöki diatomite, the Chert Member and the Groisenbach Member differs greatly, although all units are deposited in silled basins.

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Secular evolution of the lithospheric mantle beneath the northern margin of the North China Craton: Insights from zoned olivine xenocrysts in Early Cretaceous basalts

Geological Society of America Bulletin ◽

10.1130/b35443.1 ◽

2020 ◽

Vol 132 (11-12) ◽

pp. 2353-2366

Author(s):

Yao Xu ◽

Hongfu Zhang

Keyword(s):

Early Cretaceous ◽

North China Craton ◽

Lithospheric Mantle ◽

North China ◽

Mantle Xenoliths ◽

Liaoning Province ◽

Northern Margin ◽

Secular Evolution ◽

The North ◽

Peridotitic Mantle

Abstract Abundant zoned olivine xenocrysts from Early Cretaceous basalts of the Yixian Formation in western Liaoning Province, China, contain critical information about the nature and evolution of the lithospheric mantle of the northern North China Craton. These olivine xenocrysts are large (600–1600 µm), usually rounded and embayed, with well-developed cracks. Their cores have high and uniform forsterite (Fo) contents (88–91), similar to the peridotitic olivine entrained by regional Cenozoic basalts. Their rims have much lower Fo contents (74–82), comparable to phenocrysts (72–81) in the host basalts. These characteristics reveal that the zoned olivine has been disaggregated from mantle xenoliths and thus can be used to trace the underlying lithospheric mantle at the time of basaltic magmatism. The olivine cores have high oxygen isotope compositions (δ18OSMOW = 5.9–7.0‰) relative to the normal mantle value, suggesting that the Early Cretaceous lithospheric mantle was enriched and metasomatized mainly by melts/fluids released from subducted oceanic crust that had experienced low-temperature hydrothermal alteration. Preservation of zoned olivine xenocrysts in the Early Cretaceous basalts indicates that olivine-melt/fluid reaction could have been prevalent in the lithospheric mantle as an important mechanism for the transformation from old refractory (high-Mg) peridotitic mantle to young, fertile (low-Mg), and enriched lithospheric mantle during the early Mesozoic.

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Archean-Paleoproterozoic Lithospheric Mantle at the Northern Margin of the North China Craton Represented by Tectonically Exhumed Peridotites

Acta Geologica Sinica - English Edition ◽

10.1111/1755-6724.13449 ◽

2017 ◽

Vol 91 (6) ◽

pp. 2041-2057 ◽

Cited By ~ 5

Author(s):

Wei TIAN ◽

Shuangyue WANG ◽

Fenglin LIU ◽

Zhuyin CHU ◽

Bin WANG ◽

...

Keyword(s):

North China Craton ◽

Lithospheric Mantle ◽

North China ◽

Northern Margin ◽

The North

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Metasomatic History of the Lithospheric Mantle beneath the Styrian Basin (W-Pannonian Basin)

10.46427/gold2020.74 ◽

2020 ◽

Author(s):

László Előd Aradi ◽

Eniko Bali ◽

Marta Berkesi ◽

Alberto Zanetti ◽

Csaba Szabó

Keyword(s):

Lithospheric Mantle ◽

Pannonian Basin ◽

Styrian Basin ◽

History Of

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Geochemical and Sr-Nd isotopic characteristics of the lamprophyre in the Tethyan Himalaya, South Tibet

10.5194/egusphere-egu2020-12552 ◽

2020 ◽

Author(s):

Zhi-Chao Liu ◽

Jian-Gang Wang ◽

Xiao-Chi Liu

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Lithospheric Mantle ◽

Indian Plate ◽

Late Triassic ◽

Geochemical Data ◽

Low Grade ◽

Northern Margin ◽

Two Samples ◽

Tethyan Himalaya

A lamprophyre dyke has been found in Ramba area within the Tethyan Himalaya. It intruded into the Late Triassic low-grade metasedimentary rocks (Langjiexue Group) and show typical porphyritic textures, with phlogopite as the dominant phenocrysts. In this study, we performed phlogopite 40Ar/39Ar dating and whole-rock major and trace element as well as Sr and Nd isotope geochemical analyses on the lamprophyre. The 40Ar/39Ar plateau ages (13.1 &#177; 0.2 Ma and 13.5 &#177; 0.2 Ma) of the phlogopites from two samples are both in excellent agreement with the inverse isochron ages of 13.1 &#177;0.3 Ma and 13.6 &#177; 0.3 Ma, recording the times at which the lamprophyre dyke has cooled below ~300 &#176;C. The lamprophyre has low contents of SiO2 (51.43&#8211;55.15 wt%) and Al2O3 (11.10&#8211;11.85 wt%), high Fe2O3T (8.57&#8211;9.27 wt%) and MgO (9.14&#8211;9.49 wt %) contents with Mg# of 66&#8211;69, higher content of K2O (3.26&#8211;5.57 wt%) relative to Na2O (0.50&#8211;1.39 wt%) with K2O/Na2O of 2.3&#8211;11.1. Furthermore, the lamprophyre has high abundances of large ion lithophile elements (e.g., Rb, Ba, Sr), shows depletions in high field strength elements (e.g., Nb, Ta, Ti), and displays enrichment in light rare-earth elements over heavy rare earth elements with (La/Yb)N of 42.3~47.0. Besides, the lamprophyre is characterized by high initial 87Sr/86Sr ratios of 0.7196~0.7204 and negative &#949;Nd(t) values of -10.7~-10.8. Geochemical data suggest that the Ramba lamprophyre was likely generated by partial melting of a metasomatized, phlogopite-bearing harzburgite lithospheric mantle source, followed by crystal fractionation and varying degree of crustal assimilation. The studied lamprophyre provides a window into the composition of the subcontinental lithospheric mantle (SCLM) in the northern margin of the Indian plate. We suggest that the northern Indian plate might be involved in the Andean-type orogeny from the subduction of the Proto-Tethys Ocean during Cambrian to Early Ordovician.

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