scholarly journals Geology of the Southern "Muro Volcanic Area" with special reference to the characteristics of the Volcanic Rocks

1960 ◽  
Vol 66 (772) ◽  
pp. 1-16 ◽  
Author(s):  
Isao SHIIDA ◽  
Yoshio ARAKI ◽  
Kazuo HUZITA ◽  
Minoru ITIHARA ◽  
Taro KASAMA ◽  
...  
Keyword(s):  
Special Reference ◽  
Volcanic Rocks ◽  
Volcanic Area

scholarly journals Hydrogeology and hydrogeochemistry of an alkaline volcanic area: the NE Mt. Meru slope (East African Rift – Northern Tanzania)

2011 ◽  
Vol 8 (5) ◽  
pp. 8255-8289 ◽  
Author(s):  
G. Ghiglieri ◽  
D. Pittalis ◽  
G. Cerri ◽  
G. Oggiano
Keyword(s):  
Major Ions ◽  
Volcanic Rocks ◽  
Volcanic Area ◽  
East African ◽  
Geochemical Composition ◽  
Fine Grained ◽  
Physico Chemical ◽  
Northern Tanzania ◽  
Hydraulic Gradients ◽  
African Rift

Abstract. The objective of this study is to analyze the geochemical conditions associated with the presence of fluoride (F−) in the groundwater of an area of Northern Tanzania. The studied aquifers are composed of volcanic rocks such as phonolitic and nephelinitic lavas, basalts, lahars of various ages and mantling ash. Sedimentary rocks consisting of fine-grained alluvial and lacustrine deposits occur as well. Samples collected from springs, borehole and surface water, during two monitoring surveys, were analyzed for the various physico-chemical and isotopic parameters. The geochemical composition of water is typically sodium bicarbonate. High values of F− (up to 68 mg l−1) were recorded. The highest values of fluoride agreed with the highest values of pH, sodium and bicarbonate. Dissolution of major ions, exchange processes and precipitation of Ca2+ from super-saturated solutions joined with the local permeability and hydraulic gradients, control the fluoride mobilization and the contamination of the area.

scholarly journals III.—A New British Phonolite

1892 ◽  
Vol 9 (4) ◽  
pp. 149-150 ◽  
Author(s):  
Frederick H. Hatch
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Area ◽  
Lower Carboniferous ◽  
Working Out

In working out, at the request of Sir Archibald Geikie, the petrography of the Lower Carboniferous Volcanic rocks in Haddingtonshire (the results of which I propose shortly to publish), I have been led to examine the igneous material that builds up the isolated hills (necks), situated on the margin of the volcanic area of the Garlton Hills. Among these, the rock of Traprain Law especially attracted my attention. It is a close-grained, dark brown to grey rock. Some varieties have a glistening or greasy surface, and are speckled over with dark spots, while others show glancing cleavage surfaces of a clear glassy felspar (sanidine).

Petrology of Basanitic Lavas of the Daur–Hentiyn Range (P–T Conditions of Formation, Crystallization Sequence, and Sources of Material)

2021 ◽  
Vol 62 (03) ◽  
pp. 291-305
Author(s):  
A.Ya. Medvedev ◽  
E.I. Demonterova ◽  
A.A. Karimov ◽  
V.A. Belyaev
Keyword(s):  
Electron Probe ◽  
Volcanic Rocks ◽  
Oceanic Island ◽  
Volcanic Area ◽  
Crystallization Sequence ◽  
Nd Isotope ◽  
Mineral Compositions ◽  
Oceanic Island Basalts ◽  
South Baikal ◽  
Comprehensive Study

Abstract —We performed a comprehensive study of basanites from the Daur–Hentiyn Range and present the first data on their Sr and Nd isotope and mineral compositions (electron probe microanalysis). The study has shown that the basanites are chemically similar to the volcanic rocks of the South Baikal volcanic area (SBVA) and are slightly different from oceanic island basalts in higher contents of Ba, Th, La, and Sr. The crystallization temperatures and pressures for the Fo0.85 olivine–melt equilibrium have been estimated, 1186–1137 ºC, 1.09–1.06 GPa, and the sequence of mineral crystallization has been established. The obtained Sr and Nd isotope data indicate that the basanitic magmas were generated from material with PREMA and EMI isotope parameters.

scholarly journals Geological, Geochemical, and Mineralogical Constraints on the Genesis of the Polymetallic Pb-Zn-Rich Nuocang Skarn Deposit, Western Gangdese, Tibet

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 839
Author(s):  
Junsheng Jiang ◽  
Shunbao Gao ◽  
Youye Zheng ◽  
David R. Lentz ◽  
Jian Huang ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Meteoric Water ◽  
Ph Value ◽  
Volcanic Rocks ◽  
Volcanic Area ◽  
Skarn Deposit ◽  
Epithermal Deposits ◽  
Magmatic Fluids ◽  
Magmatic Volatiles ◽  
Geochemical Analyses

The Nuocang Pb-Zn deposit is a newly discovered polymetallic skarn deposit in the southern Lhasa subterrane, western Gangdese, Tibet. The skarn occurs at the contact between the limestone of Angjie Formation and the Linzizong volcanic rocks of Dianzhong Formation (LDF), and the subvolcanic granite porphyry intruding those formations; the contact metasomatic skarn is well zoned mineralogically and texturally, as well as geochemically. The skarn minerals predominantly consist of an anhydrous to hydrous calc-silicate sequence pyroxene–garnet–epidote. The endoskarn mainly consists of an assemblage of pyroxene, garnet, ilvaite, epidote, and quartz, whereas the exoskarn is characterized proximal to distally, by decreasing garnet, and increasing pyroxene, ilvaite, epidote, chlorite, muscovite, quartz, calcite, galena, and sphalerite. Geochemical analyses suggest that the limestone provided the Ca for all the skarn minerals and the magmatic volatiles were the main source for Si (except the skarnified hornfels/sandstone, and muscovite-epidote-garnet-pyroxene skarn possibly from the host sandstones), with Fe and Mn and other mineralizing components. During the hydrothermal alteration, the garnet-pyroxene skarn and pyroxene-rich skarn gained Si, Fe, Mn, Pb, Zn, and Sn, but lost Ca, Mg, K, P, Rb, Sr, and Ba. However, the skarnified hornfels/sandstone, and muscovite-epidote-garnet-pyroxene skarn gained Fe, Ca, Mn, Sr, Zr, Hf, Th, and Cu, but lost Si, Mg, K, Na, P, Rb, Ba, and Li. The REEs in the skarn were sourced from magmatic fluids during the prograde stage. Skarn mineral assemblages and geochemistry indicate the skarn in the Nuocang deposit were formed in a disequilibrated geochemical system by infiltrative metasomatism of magmatic fluids. During the prograde stage, garnet I (And97.6Gro1.6) firstly formed, and then a part of them incrementally turned into garnet II (And64.4Gro33.8) and III (And70.22Gro29.1). The subsequent substitution of Fe for Al in the garnet II and III indicates the oxygen fugacity of the fluid became more reduced, then resulted in formation of significant pyroxene. However, the anisotropic garnet IV (And38.5Gro59.8) usually replaced the pyroxene. In the retrograde stage, the temperature decreased and oxygen fugacity increased, but hydrolysis increased with epidote, ilvaite, chlorite I, and muscovite forming with magnetite. The continuing decreasing temperature and mixing with meteoric water lead to Cu, Pb, and Zn saturation as sulfides. After the sulfides deposition, the continued mixing with large amounts of cold meteoric water would decrease its temperature, and increase its pH value (neutralizing), promoting the deposition of significant amounts of calcite and chlorite II. The geological, mineralogical, and geochemical characteristics of Nuocang skarn, suggest that the Nuocang deposit is of a Pb-Zn polymetallic type. Compared to the other typical skarn-epithermal deposits in the Linzizong volcanic area, it indicates that the Nuocang deposit may have the exploration potential for both skarn and epithermal styles of mineralization.

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