Petrology and major element geochemistry of high-K peraluminous granites in southeast Obudu plateau, southeastern Nigeria

2009 ◽  
Vol 44 (2) ◽  
Author(s):  
FT Beka ◽  
VU Ukaegbu
Keyword(s):  
Major Element ◽  
Element Geochemistry ◽  
Southeastern Nigeria ◽  
High K ◽  
Peraluminous Granites

Trace and Major Element Geochemistry of Basalts from Leg 81

1984 ◽  
Author(s):  
C. Richardson ◽  
P.J. Oakley ◽  
J.R. Cann
Keyword(s):  
Major Element ◽  
Element Geochemistry

scholarly journals Rare sapphire-bearing syenitoid pegmatites and associated granitoids of the Hamedan region, Sanandaj–Sirjan zone, Iran: analysis of petrology, lithogeochemistry and zircon geochronology / trace element geochemistry

2020 ◽  
Vol 157 (9) ◽  
pp. 1499-1525 ◽  
Author(s):  
Ali A Sepahi ◽  
Hamed Vahidpour ◽  
David R Lentz ◽  
Chris RM McFarlane ◽  
Mohammad Maanijou ◽  
...  
Keyword(s):  
Trace Element ◽  
Trace Element Geochemistry ◽  
Chemical Compositions ◽  
Zircon Geochronology ◽  
Element Geochemistry ◽  
High K ◽  
Igneous Origin ◽  
Plutonic Complex ◽  
Sanandaj Sirjan Zone ◽  
Zircon Thermometry

AbstractPegmatites and associated granitoids are integral parts of the Alvand plutonic complex in the Sanandaj–Sirjan zone, Iran. Whole rock major- and trace-element lithogeochemistry together with zircon U–Pb geochronology and zircon geochemistry are examined to evaluate the petrogenesis of sapphire-bearing pegmatites and other peraluminous pegmatites in the region. Pegmatites vary in their chemical compositions from mostly peraluminous, high-K calc-alkaline to shoshonitic signatures. A rare variety of extremely peraluminous sapphire-bearing syenitoid pegmatite (Al2O3 > 30 wt %; A/CNK > 2) exists. This silica-undersaturated pegmatite and its sapphire crystals have a primary igneous origin. U–Pb zircon geochronology of three separate samples from this pegmatite indicates the following ages: 168 ± 1 Ma, 166 ± 1 Ma and 164 ± 1 Ma. The zircon grains have notable amounts of Hf (up to 17 200 ppm), U (up to 13 580 ppm), Th (up to 5148 ppm), Y (up to 4764 ppm) and ∑REE (up to 2534 ppm). There is a positive correlation between Hf and Th, Nb and Ta, U and Th, and Y and HREE and a negative correlation between Hf and Y values in the zircons. These zircons exhibit pronounced positive Ce anomalies (Ce/Ce* = 1.15–68.06) and negative Eu anomalies (Eu/Eu* = 0.001–0.56), indicative of the relatively oxidized conditions of the parent magma. Ti-in-zircon thermometry reveals temperatures from as low as ~683 °C up to ~828 °C (average = 755° ± 73 °C). Zircon and monazite saturation equilibria are also consistent with these temperatures. Zircon grains are magmatic (average La < 1.5, (Sm/La)N > 100 and Th/U > 0.7), with chemical characteristics similar to zircons from continental crust.

Characterization and dispersal of indicator minerals associated with the Pine Point Mississippi Valley-type (MVT) district, Northwest Territories, Canada

2015 ◽  
Vol 52 (9) ◽  
pp. 776-794 ◽  
Author(s):  
N.M. Oviatt ◽  
S.A. Gleeson ◽  
R.C. Paulen ◽  
M.B. McClenaghan ◽  
S. Paradis
Keyword(s):  
Northwest Territories ◽  
Major Element ◽  
Bimodal Distribution ◽  
Mississippi Valley ◽  
Element Geochemistry ◽  
Element Concentrations ◽  
Pine Point ◽  
Indicator Minerals ◽  
Mississippi Valley Type ◽  
Valley Type

A glacial dispersal study was conducted around a subcropping Pb–Zn deposit (O28) in the Pine Point Mississippi Valley-type (MVT) district, Northwest Territories, Canada, with the intent of characterizing and documenting the indicator minerals and their dispersal from a known orebody. Mapping of striations adjacent to deposit O28, and throughout the Pine Point district, along with observed glacial stratigraphy, indicate that there are three phases of ice flow that have affected the Pine Point district. Sphalerite, galena, and pyrite were identified in mineralized bedrock samples at deposit O28, and sphalerite and galena were recovered from the sand fraction of till samples up to 500 m from the mineralized subcrop. The majority of sphalerite and galena grains recovered from till samples down-ice of deposit O28 were 0.25–0.5 mm in size. Size and morphology of sphalerite grains in till demonstrate relative proximity to their bedrock source, with the largest and more angular grains being closer to the ore zone (<50 m) whereas smaller and more rounded grains occur further down-ice (∼250 m). The paragenesis, textures, major-element concentrations, and S and Pb isotopic compositions of bedrock samples from deposit O28 and from newly drilled core from four other deposits were characterized. Concentrations of Zn in bedrock sphalerite grains range from 43.95 to 67.48 wt.%, concentrations of S range from 32.03 to 34.01 wt.%, and concentrations of Fe range from 0.02 to 16.94 wt.%. The Fe concentration in bedrock sphalerite decreases from east to west across the district. Concentrations of S in galena grains in bedrock range from 12.50 to 14.00 wt.% and have a bimodal distribution. Generally, the geochemistry of sphalerite grains recovered from till were statistically similar to bedrock grains recovered from deposits O28 and L65. Major-element concentrations were statistically the same between the sphalerite grains recovered from till and the honey-brown and cleiophane varieties in the bedrock samples. Galena grains recovered from till samples were similar to the cubic and fracture-fill varieties of grains recovered from bedrock in the R190 and M67 deposits. Sulphur isotopic values for sphalerite grains from bedrock range from 20.6‰ to 24.2‰, while those from till samples range from −5.3‰ to 24.4‰. Lead isotopic ratios for galena grains from bedrock and till samples had very little variation, which is a characteristic of the Pine Point district. The S and Pb isotopic studies as well as major-element geochemistry suggest that indicator minerals derived from Pine Point-type mineralization can be distinguished from those sourced from other types of carbonate-hosted mineralized systems (e.g., Cordilleran zinc–lead deposits) and that the methods here can be used as exploration tools for identifying MVT deposit provenance or potential. The results of this study present criteria and highlights additional methods for exploration of MVT deposits in glaciated terrain.

Geochemical aspects of the Santonian Chalk of Ramsgate, England, and the origin of the chert and clay minerals

1979 ◽  
Vol 43 (325) ◽  
pp. 159-164 ◽  
Author(s):  
D. A. Spears
Keyword(s):  
Clay Minerals ◽  
Upper Cretaceous ◽  
Major Element ◽  
Clay Content ◽  
Carbonate Content ◽  
Element Geochemistry ◽  
Carbonate Sedimentation ◽  
Volcanic Debris ◽  
The Mean

SummaryThe mineralogy and major-element geochemistry of thirty-seven samples from a borehole in the Upper Cretaceous Chalk (Santonian) of Kent has been determined. The mean carbonate content is 97% and the carbonate is a low-Mg calcite (0.42 mol % MgCO3). Most of the silica is deduced to be biogenic chert. The total clay content probably varies through the sequence due to changes in the rate of carbonate sedimentation. The clay composition remains relatively constant with smectite more abundant than illite. The smectite and K-feldspar could be formed from volcanic debris whereas illite and quartz are thought to be detrital.

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