Provenance change in the Irkutsk coal basin during the early and middle Jurassic: Geochemical and Sm-Nd isotope evidence

2017 ◽  
Vol 25 (4) ◽  
pp. 363-384 ◽  
Author(s):  
E. A. Mikheeva ◽  
E. I. Demonterova ◽  
A. O. Frolov ◽  
A. V. Arzhannikova ◽  
S. G. Arzhannikov ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Coal Basin ◽  
Nd Isotope ◽  
Irkutsk Coal Basin ◽  
Isotope Evidence

Sorosaccus sibiricus Prynada (Ginkgoales) from the Middle Jurassic deposits of the Irkutsk Coal Basin, Eastern Siberia

Palaeobotany ◽  
2018 ◽  
Vol 9 ◽  
pp. 5-17
Author(s):  
N. V. Nosova ◽  
N. M. Zavialova ◽  
A. I. Kiritchkova ◽  
E. I. Kostina
Keyword(s):  
Middle Jurassic ◽  
Pollen Grains ◽  
Eastern Siberia ◽  
Coal Basin ◽  
New Findings ◽  
Irkutsk Coal Basin ◽  
First Time

New findings of pollen cones of Sorosaccus sibiricus Prynada were studied in detail from the Aalenian—Bajocian Prisayan Formation of two localities in the Irkutsk coal basin (Ust’-Baley and Vladimirovka). Specimens of S. sibiricus previously described from Ust’-Baley (Heer, 1876) were reexamined. It was revealed that S. sibiricus differs from other species of Sorosaccus in a shape of the apical (free from the microsporangia) part of the microsporophylls. Microsporophylls of S. sibiricus consist of a petiole and a wide-oval distal lamina with acute apex, commonly bending upward. The lamina was often folded and became lanceolate, linear, or fan-shaped with uneven to toothed margin. Microsporangia (6—8) are oval in outline, helically attached to the petiole. Pollen grains were extracted from S. sibiricus microsporangia for the first time. They are oval to boat-shaped in outline, monosulcate and differ from other known Sorosaccus pollen grains by the verrucate surface of the exine. The diagnosis of the species Sorosaccus sibiricus is emended.

scholarly journals The first discovery leaves of angiosperms in the Middle Jurassic deposits in Eastern Siberia

2020 ◽  
Author(s):  
А.О. Frolov ◽  
◽  
I.V. Enushchenko ◽  
Keyword(s):  
Middle Jurassic ◽  
Eastern Siberia ◽  
Coal Basin ◽  
Anomocytic Stomata ◽  
Irkutsk Coal Basin

There is fossil of linear whole-marginal leaves with parallel venation in the Middle Jurassic (Aalenian) sediments of the Irkutsk Coal Basin, were found. During the study of cuticle preparations it was found that leaves were steam-bearing, has anastomoses between veins, anomocytic stomata and the diamond-shaped main cells of the epidermis. Such a combination of characters is widespread in modern monocotyledonous and is absent among fossil as well as modern sporeals and gymnosperms plants. We have every reason to believe that we have found unique structures of leaves characteristic of monocotyledons. This find is the oldest among the herbaceous angiosperms of the Jurassic period, such as Yuraherba and Yukhaniya, and the first found in Siberia.

Rare earth element, Sr- and Nd-isotope evidence for petrogenesis of Permian basaltic and K-rich volcanic rocks from south-west England

1986 ◽  
Vol 50 (357) ◽  
pp. 481-489 ◽  
Author(s):  
R. S. Thorpe ◽  
M. E. Cosgrove ◽  
P. W. C. van Calsteren
Keyword(s):  
High Field ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Transition Element ◽  
Oceanic Lithosphere ◽  
High Field Strength ◽  
Nd Isotope ◽  
South West ◽  
Isotope Evidence ◽  
South West England

AbstractPermian basic/ultrabasic lavas from south-west England may be divided into a ‘basaltic’ and a K-rich group. Both groups have enrichment of large-ion lithophile (LIL) elements relative to high field strength (HFS) elements, and the K-rich group show large degrees of LIL enrichment (c.50–500 times primordial mantle) in association with varied transition element concentrations. Samples from both groups 87Sr/86Sri = 0.704–0.705 and 143Nd/144Ndi = 0.5123–0.5127 and plot close to the mantle array on an ɛSr−ɛNd diagram. These data are interpreted in terms of derivation of the lavas from magmas resulting from partial melting of mantle which had experienced less (for the basaltic group) or more (for the K-rich group) enrichment in LIL elements as a result of migration of mantle melts. Such enrichment accompanied or followed subduction of oceanic lithosphere below south-west England. The resultant magmas experienced fractional crystallization of olivine and pyroxene prior to eruption.

Isotope evidence for the origin of Andean granites

1988 ◽  
Vol 79 (2-3) ◽  
pp. 123-133 ◽  
Author(s):  
R. J. Pankhurst ◽  
M. J. Hole ◽  
M. Brook
Keyword(s):  
Antarctic Peninsula ◽  
Nd Isotope ◽  
Depleted Mantle ◽  
Wide Range ◽  
Mantle Sources ◽  
Subducted Oceanic Crust ◽  
Isotope Evidence ◽  
The Antarctic ◽  
Isotope Systematics ◽  
Material Input

ABSTRACTThe genesis of subduction-related magmas in the Andean region of South America and the Antarctic Peninsula is considered in relation to the Palaeozoic to Cenozoic granitoids belts which are thought to parallel palaeo-coastlines. Their Sr-Nd isotope systematics show a wide range of initial compositions (87Sr/86Sr0 0·7038 to >0·710; εNd, +4 to –10) requiring material input from both depleted mantle and continental crust. In local transects there are consistent trends with time of emplacement, from enriched (crustal) to depleted (mantle) sources, regardless of the sense of migration of magmatism (towards or away from the continent). These trends represent mixing between mantle-derived material and anatectic melts of the lower crust: in each case the crustal end-member reflects the age and isotopic composition of the local deep crustal basement (Precambrian in the easternmost Andes, Palaeozoic in the W and in the Antarctic Peninsula). The depleted end-member could be derived by melting within the subducted oceanic crust, the overlying mantle or previously crystallised mafic underplating. One of the most important factors controlling the mixing process is the angle of subduction, resulting in magma generation under variable tectonic conditions.

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