scholarly journals Late stages in the evolution of the late Mesozoic East Mongolian volcanic areal: rock age and composition

2019 ◽  
Vol 487 (3) ◽  
pp. 283-288
Author(s):  
V. V. Yarmolyuk ◽  
E. A. Kudryashova ◽  
A. M. Kozlovsky
Keyword(s):  
Late Cretaceous ◽  
Lithospheric Mantle ◽  
Alkali Basalt ◽  
Lava Flows ◽  
Late Mesozoic ◽  
Formation History ◽  
Magma Sources ◽  
Late Stages ◽  
Early Cenozoic ◽  
Basalt Magmatism

The Mandakh-Madal-Gobi (MMG) zone of alkali basalt magmatism has been delineated in the Late Mesozoic East Mongolian volcanic areal. It comprises clusters of igneous rock bodies and isolated stocks, domes, sills, laccoliths, dikes, and limited fragments of lava flows composed of tephrite, phono-tephrite, and trachybasalt. Two pulses of magmatism in the MMG zone have occurred in the Late Cretaceous (about 85 Ma) and Early Cenozoic (about 50 Ma). Recognition of this zone and deciphering of its formation history demonstrated that the development of the entire East Mongolian volcanic areal had the same regularities as those identified in other major regions of the Late Mesozoic Central Asia magmatic province. This indicates that the areal undoubtedly belongs to the latter. These facts support the conclusion that the correlation observed through the zone’s evolution between reduction in the volume of igneous products and the change in their composition towards the OIB was apparently determined by a decrease in the effect of thermal sublithospheric mantle melts upon a metasomatically enriched lithospheric mantle, leading to its gradual elimination from the magma sources.

scholarly journals Geochemical comparison of late Mesozoic and early Cenozoic volcanic rocks in South Mongolia

2019 ◽  
pp. 3-21
Author(s):  
Togtokh Khasmaral ◽  
Bars Amarjargal ◽  
Laicheng Miao ◽  
Baatar Munkhtsengel ◽  
Anaad Chimedtseren
Keyword(s):  
East Asia ◽  
Late Cretaceous ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Northern Margin ◽  
Late Mesozoic ◽  
The North ◽  
Tectonic Transition ◽  
Cenozoic Volcanism ◽  
Early Cenozoic

The Mesozoic-Cenozoic volcanic rocks are widely distributed in the interior of the East Asia and document the tectonic transition of East Asia. We present new geochronology and geochemistry data of late Cretaceous-early Cenozoic basalts in Bayantsagaan and Han-Uul volcanic provinces in South Mongolia, in order to explore their petrogenesis and geodynamic settings. The volcanic rocks in the Bayantsagaan and Han-Uul field yielded K-Ar ages of 90.55±1.93 Ma and 55.49±1.49 Ma, respectively. The volcanic rocks in South Mongolia can be subdivided into to alkaline basalts and tholeiitic series, and are characterized by ocean island basalts (OIB) trace elements features, such as enrichment of light REE relative to heavy REE and enrichment in large ion lithophile elements (LILE) with positive K anomaly. Compared with the late Cretaceous, the early Cenozoic basalts show a decrease in the contents of HREE and an increase of Nb and Ta. Crustal contamination and fractional crystallization are insignificant in the genesis of late Cretaceous-early Cenozoic basalts South Mongolia. The available Sr-Nd isotope results indicate that a mixing depleted (DM) and enriched mantle (EM) signature characterize in late Cretaceous volcanic rocks, which derived from magmas from the asthenosphere with some contributions of metasomatized subcontinent lithospheric mantle, whereas the early Cenozoic basalts are ascribed to contributions from the asthenospheric mantle. We propose that the generation of the late Cretaceous-early Cenozoic volcanism (90-40 Ma) in Mongolia is probably related to the shallow mantle upwelling (asthenosphere) induced by the edge convection along the northern margin of the North China Craton (NCC), triggered by a far-field effect of Indo-Asian collision.

scholarly journals Integrated geophysical investigations of deeper stratigraphy of the Irish Rockall Basin

2021 ◽  
Author(s):  
Gaurav Tomar ◽  
Srikumar Roy ◽  
Christopher J. Bean ◽  
Satish C. Singh ◽  
Brian O'Reilly ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Sedimentary Basins ◽  
Moho Depth ◽  
The South ◽  
Data Set ◽  
Late Mesozoic ◽  
The North ◽  
Stretching Factor ◽  
The Uk ◽  
Early Cenozoic

<p>The Rockall Trough is an elongate bathymetric depression trending NNE-SSW. It is approximately 1200 km long and up to 300 km wide, extending over the UK and Irish continental margins. The trough is underlain by the Rockall Basin, which forms part of a chain of late Paleozoic-Cenozoic sedimentary basins. The Irish Rockall Basin is vastly unexplored as compared to the UK sector, where extensive flood basalt lava flows, sill complexes and volcanic centers of Late Cretaceous-to-Early Eocene age have been described, which belong to the North Atlantic Igneous Province (NAIP) (Archer et al., 2005). An integrated study of seismic, gravity and magnetic methods elucidates the deeper stratigraphy of the Irish Rockall Basin. More than 10 km of sediments is present in the central part of the basin. We perform first arrival travel time tomography on a downward continued data set of three seismic profiles to model the velocity of the sedimentary structures down to 6 km depth. To better understand the deep structure of the basin we need to estimate the Moho depth from constrained gravity modelling. The modelling results indicate that the Moho depth varies from 12 km to 20 km depth beneath ~10 km thick sediments in the basin. This allows us to measure the crustal stretching factor β. The minimum stretching factor in the basin varies between ~7 in the north to ~6.5 in the south. These values are within the range needed for mantle serpentinisation (O'Reilly et al., 1996; Perez-Gussinye and Reston, 2001). Furthermore, we observe four volcanic ridges in the south part of the basin, which are ~20 km wide and ~ 3 km thick, possibly comprising the Barra Volcanic Ridge System (BVRS) (Scrutton and Bentley, 1988). Results indicate several failed rifting attempts times in late Mesozoic/early Cenozoic times, generating significant basic volcanism, associated with the NAIP. We resolve new volcanic ridges (of late Mesozoic/early Cenozoic age) in the southern part of the Rockall Basin, like many other volcanic ridges/centres observed in other parts of the basin, with correlatable magnetic and gravity anomalies. These may be of late Cretaceous age similar to those found on the conjugate Canadian margin.</p>

scholarly journals Genesis of the Late Cretaceous Longquanzhan Gold Deposit in the Central Tan-Lu Fault Zone, Shandong Province, China: Constraints from Noble Gas and Sulfur Isotopes

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 250
Author(s):  
Chuanpeng Liu ◽  
Wenjie Shi ◽  
Junhao Wei ◽  
Huan Li ◽  
Aiping Feng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Late Cretaceous ◽  
Genetic Model ◽  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Noble Gas ◽  
Gold Deposits ◽  
Shandong Province ◽  
Magma Sources

The Longquanzhan deposit is one of the largest gold deposits in the Yi-Shu fault zone (central section of the Tan-Lu fault zone) in Shandong Province, China. It is an altered-rock type gold deposit in which ore bodies mainly occur at the contact zone between the overlying Cretaceous rocks and the underlying Neoarchean gneissic monzogranite. Shi et al. reported that this deposit formed at 96 ± 2 Ma using pyrite Rb–Sr dating method and represents a new gold mineralization event in the Shandong Province in 2014. In this paper, we present new He–Ar–S isotopic compositions to further decipher the sources of fluids responsible for the Longquanzhan gold mineralization. The results show that the δ34S values of pyrites vary between 0.9‰ and 4.4‰ with an average of 2.3‰. Inclusion-trapped fluids in ore sulfides have 3He/4He and 40Ar/36Ar ratios of 0.14–0.78 Ra and 482–1811, respectively. These isotopic data indicate that the ore fluids are derived from a magmatic source, which is dominated by crustal components with minor mantle contribution. Air-saturated water may be also involved in the hydrothermal system during the magmatic fluids ascending or at the shallow deposit site. We suggest that the crust-mantle mixing signature of the Longquanzhan gold deposit is genetically related to the Late Cretaceous lithospheric thinning along the Tan-Lu fault zone, which triggers constantly uplifting of the asthenosphere surface and persistent ascending of the isotherm plane to form the gold mineralization-related crustal level magma sources. This genetic model can be applied, to some extent, to explain the ore genesis of other deposits near or within the Tan-Lu fault belt.

Dispersal of Vertebrates from Between the Americas, Antarctica, and Australia in the Late Cretaceous and Early Cenozoic

2015 ◽  
pp. 77-124 ◽  
Author(s):  
Francisco J. Goin ◽  
Michael O. Woodburne ◽  
Ana Natalia Zimicz ◽  
Gabriel M. Martin ◽  
Laura Chornogubsky
Keyword(s):  
Late Cretaceous ◽  
Early Cenozoic

scholarly journals New Late Cretaceous and Early Cenozoic decapod crustaceans from California, USA: implications for the origination of taxa in the eastern North Pacific

2003 ◽  
Vol 72 (2-3) ◽  
pp. 165-168 ◽  
Author(s):  
Torrey G. Nyborg ◽  
Francisco J. Vega ◽  
Harry F. Filkorn
Keyword(s):  
New Species ◽  
Los Angeles ◽  
Natural History ◽  
Late Cretaceous ◽  
North Pacific ◽  
Los Angeles County ◽  
Pivotal Role ◽  
Decapod Crustaceans ◽  
History Museum ◽  
Early Cenozoic

Recent revision of Cretaceous and Paleocene brachyurans in the collections of the Natural History Museum of Los Angeles County has revealed the presence of several new species. Based upon these fossils and their ages, it is evident that they played a pivotal role in the origination and subsequent dispersal of decapod crustaceans within the eastern North Pacific.

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