INTERACTION OF CRUSTAL AND MANTLE MATERIALS, SOURCES OF TRACE ELEMENTS DURING THE FORMATION AND EVOLUTION OF EARLY PALEOZOIC Li-RICH GRANITE-PEGMATITE SYSTEMS IN SOUTHEASTERN TUVA

2018 ◽  
Vol 59 (12) ◽  
pp. 2079-2100
Author(s):  
L.G. Kuznetsova
Keyword(s):  
Trace Elements ◽  
Early Paleozoic ◽  
Granite Pegmatite ◽  
Formation And Evolution

scholarly journals The Early Silurian Gabbro in the Eastern Kunlun Orogenic Belt, Northeast Tibet: Constraints on the Proto-Tethyan Ocean Closure

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 794
Author(s):  
Wenxiao Zhou ◽  
Haiquan Li ◽  
Feng Chang ◽  
Xinbiao Lv
Keyword(s):  
Evolutionary History ◽  
Orogenic Belt ◽  
Early Paleozoic ◽  
High Field Strength ◽  
Geochemical Composition ◽  
Eastern Segment ◽  
History Of ◽  
Formation And Evolution ◽  
Light Rare Earth Elements ◽  
Final Closure

The early Paleozoic is a crucial period in the formation and evolution of the Eastern Kunlun Orogenic Belt (EKOB), and is of great significance for understanding the evolutionary history of the Proto-Tethyan Ocean. This paper presents new petrography, geochemistry, zircon U–Pb dating, and Lu–Hf isotopic research on the Yuejingshan gabbro from the eastern segment of the EKOB. Zircon U–Pb data suggests that the gabbro formed in the Early Silurian (435 ± 2 Ma). All samples have relatively low TiO2 contents (0.45–2.97%), widely varying MgO (6.58–8.41%) and Mg# (58–65) contents, and are rich in large ion lithophile elements (LILE such as Rb, Ba, Th, and U) and light rare earth elements (LREE). This indicates that it has a similar geochemical composition to island arc basalt. The major element features indicate that the formation of this gabbro underwent fractional crystallization of clinopyroxene, olivine, and plagioclase. The depletion of high field strength elements (HFSE, such as Nb, Ta, and Ti), and a slightly positive Hf isotope (with εHf(t) ranging from 1.13 to 2.45) may be related to the partial melting of spinel-bearing peridotite, led by slab fluid metasomatism. The gabbro likely represents magmatic records of the latest period of the early Paleozoic oceanic crust subduction in the Eastern Kunlun. Therefore, the final closure of the Proto-Tethyan Ocean and the beginning of collisional orogeny occurred before the Early Silurian.

scholarly journals The Early Silurian Gabbro in the Eastern Kunlun Orogenic Belt, Northeast Tibet: Constraints on the Proto-Tethyan Ocean Closure

2020 ◽  
Author(s):  
Wenxiao Zhou ◽  
Haiquan Li ◽  
Feng Chang ◽  
Xinbiao Lv
Keyword(s):  
Oceanic Crust ◽  
Isotope Composition ◽  
Major Elements ◽  
Orogenic Belt ◽  
Early Paleozoic ◽  
Geochemical Composition ◽  
History Of ◽  
Formation And Evolution ◽  
Light Rare Earth Elements ◽  
Final Closure

The Early Paleozoic is a crucial period in the formation and evolution of the Eastern Kunlun Orogenic Belt (EKOB), which is of great significance for understanding the evolutionary history of the Proto-Tethyan Ocean. This paper presents new petrography, geochemistry, zircon U–Pb dating, and Lu–Hf isotopic research on the Yuejingshan gabbro from the eastern segment of the EKOB. Zircons U-Pb data suggests the gabbro formed in the Early Silurian (435 ± 2 Ma). All samples have relatively low TiO2 contents (0.45-2.97%), widely varying MgO (6.58-8.41%) and Mg# (58-65) contents, rich in large ion lithophile elements (LILE such as Rb, Ba, Th, and U) and light rare earth elements (LREE),which indicate it has a similar geochemical composition than island arc basalt. The major elements features indicate that the formation of this gabbro underwent fractional crystallization of clinopyroxene, olivine, and plagioclase. The depletion of high field strength elements (HFSE such as Nb, Ta, and Ti), and feature a slightly enriched Hf isotope composition (with εHf (t) ranging from 1.13 to 2.45) may be related to the partial melting of spinel-bearing peridotite, led by the slab fluid metasomatism. The significantly earlier than the metamorphic age (428 Ma) of the collision-related eclogite facies and the peak metamorphic age (427 Ma) of medium pressure (epidotization) amphibolite facies in the Eastern Kunlun Orogenic Belt indicates that its formation is still closely related to the subduction of the Eastern Kunlun oceanic crust. The gabbro likely represents magmatic records of the latest period of the Early Paleozoic oceanic crust subduction in the Eastern Kunlun. Therefore, the final closure of the Proto-Tethyan Ocean and the beginning of collisional orogeny, occurred before the Early Silurian.

scholarly journals The Early Silurian Gabbro in the Eastern Kunlun Orogenic Belt, Northeast Tibet: Constraints on the Proto-Tethyan Ocean Closure

2020 ◽  
Author(s):  
Wenxiao Zhou ◽  
Haiquan Li ◽  
Feng Chang ◽  
Xinbiao Lv
Keyword(s):  
Evolutionary History ◽  
Orogenic Belt ◽  
Early Paleozoic ◽  
High Field Strength ◽  
Geochemical Composition ◽  
Eastern Segment ◽  
History Of ◽  
Formation And Evolution ◽  
Light Rare Earth Elements ◽  
Final Closure

The early Paleozoic is a crucial period in the formation and evolution of the Eastern Kunlun Orogenic Belt (EKOB), and is of great significance for understanding the evolutionary history of the Proto-Tethyan Ocean. This paper presents new petrography, geochemistry, zircon U–Pb dating, and Lu–Hf isotopic research on the Yuejingshan gabbro from the eastern segment of the EKOB. Zircon U–Pb data suggests that the gabbro formed in the Early Silurian (435 ± 2 Ma). All samples have relatively low TiO2 contents (0.45–2.97%), widely varying MgO (6.58–8.41%) and Mg# (58–65) contents, and are rich in large ion lithophile elements (LILE such as Rb, Ba, Th, and U) and light rare earth elements (LREE). This indicates that it has a similar geochemical composition to island arc basalt. The major element features indicate that the formation of this gabbro underwent fractional crystallization of clinopyroxene, olivine, and plagioclase. The depletion of high field strength elements (HFSE, such as Nb, Ta, and Ti), and a slightly positive Hf isotope (with εHf(t) ranging from 1.13 to 2.45) may be related to the partial melting of spinel-bearing peridotite, led by slab fluid metasomatism. The gabbro likely represents magmatic records of the latest period of the early Paleozoic oceanic crust subduction in the Eastern Kunlun. Therefore, the final closure of the Proto-Tethyan Ocean and the beginning of collisional orogeny occurred before the Early Silurian.

Variations in Surface Textures of Quartz Sand using Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 494-495
Author(s):  
Eugene J. Amaral
Keyword(s):  
Electron Microscopy ◽  
Glass Industry ◽  
Glass Slide ◽  
Distilled Water ◽  
Early Paleozoic ◽  
Secondary Effects ◽  
Surface Textures ◽  
High Silica ◽  
Sand Deposit ◽  
The U.S

Examination of sand grain surfaces from early Paleozoic sandstones by electron microscopy reveals a variety of secondary effects caused by rock-forming processes after final deposition of the sand. Detailed studies were conducted on both coarse (≥0.71mm) and fine (=0.25mm) fractions of St. Peter Sandstone, a widespread sand deposit underlying much of the U.S. Central Interior and used in the glass industry because of its remarkably high silica purity.The very friable sandstone was disaggregated and sieved to obtain the two size fractions, and then cleaned by boiling in HCl to remove any iron impurities and rinsed in distilled water. The sand grains were then partially embedded by sprinkling them onto a glass slide coated with a thin tacky layer of latex. Direct platinum shadowed carbon replicas were made of the exposed sand grain surfaces, and were separated by dissolution of the silica in HF acid.

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