ASSESSING HYDROTHERMAL ALTERATION INTENSITY IN VOLCANIC-HOSTED MASSIVE SULFIDE SYSTEMS USING PORTABLE X-RAY FLUORESCENCE ANALYSIS OF DRILL CORE: AN EXAMPLE FROM MYRA FALLS, CANADA

2020 ◽  
Vol 115 (2) ◽  
pp. 443-453
Author(s):  
Brian A. McNulty ◽  
Nathan Fox ◽  
J. Bruce Gemmell
Keyword(s):  
Hydrothermal Alteration ◽  
Detection Limits ◽  
Fluorescence Analysis ◽  
Massive Sulfide ◽  
Hydrothermal Systems ◽  
Geochemical Data ◽  
Drill Core ◽  
Sulfide Mineralization ◽  
X Ray

Abstract Current portable X-ray fluorescence (pXRF) technology can rapidly and inexpensively yield concentrations of geologically significant elements, typically with instrument detection limits below several tens of parts per million. Based on conventional XRF whole-rock geochemical data, both the Ishikawa alteration index and the chlorite-carbonate-pyrite index increase with proximity to sulfide mineralization at Myra Falls. However, available pXRF technology is typically unable to detect all the elements required to calculate these alteration indices. As a result, there is a need to utilize the elements that are readily detectable using pXRF and apply these to hydrothermal alteration assessment. We propose that Rb/Sr ratios provide a robust proxy for the Ishikawa alteration index and demonstrate that conventional whole-rock XRF analytical results for Rb and Sr can be reproduced using pXRF analysis from drill core surfaces. At Myra Falls, the Rb/Sr ratios vary from <0.1 for least altered rocks, 0.1 to 0.5 for weakly altered rocks, 0.5 to 1.0 for moderately altered rocks, 1.0 to 2.0 for strongly altered rocks, and >2.0 for intensely altered rocks. Downhole profiles of alteration intensity generated from systematic pXRF analysis of drill core surfaces can be used to inform drilling and targeting decisions. The application of the Rb/Sr ratio as a proxy for alteration intensity extends beyond this case study and can be applied to other hydrothermal systems that produce phyllosilicate minerals as alteration products of feldspar.

scholarly journals Non-destructive handheld XRF study of archaeological composite silver objects—the case study of the late Roman Seuso Treasure

2021 ◽  
Vol 13 (5) ◽  
Author(s):  
Viktória Mozgai ◽  
Bernadett Bajnóczi ◽  
Zoltán May ◽  
Zsolt Mráv
Keyword(s):  
Fluorescence Analysis ◽  
The Body ◽  
High Quality ◽  
X Ray ◽  
Composite Objects ◽  
Mechanical Attachment ◽  
Non Destructive ◽  
Made In ◽  
Late Roman

AbstractThis study details the non-destructive chemical analysis of composite silver objects (ewers, situlas, amphora and casket) from one of the most significant late Roman finds, the Seuso Treasure. The Seuso Treasure consists of fourteen large silver vessels that were made in the fourth–early fifth centuries AD and used for dining during festive banquets and for washing and beautification. The measurements were systematically performed along a pre-designed grid at several points using handheld X-ray fluorescence analysis. The results demonstrate that all the objects were made from high-quality silver (above 90 wt% Ag), with the exception of the base of the Geometric Ewer B. Copper was added intentionally to improve the mechanical properties of soft silver. The gold and lead content of the objects shows constant values (less than 1 wt% Au and Pb). The chemical composition as well as the Bi/Pb ratio suggests that the parts of the composite objects were manufactured from different silver ingots. The ewers were constructed in two ways: (i) the base and the body were made separately, or (ii) the ewer was raised from a single silver sheet. The composite objects were assembled using three methods: (i) mechanical attachment; (ii) low-temperature, lead-tin soft solders; or (iii) high-temperature, copper-silver hard solders. Additionally, two types of gilding were revealed by the XRF analysis, one with remnants of mercury, i.e. fire-gilding, and another type without remnants of mercury, presumably diffusion bonding.

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

1984 ◽  
Vol 48 (348) ◽  
pp. 311-322 ◽  
Author(s):  
A. P. Dickin ◽  
C. M. B. Henderson ◽  
F. G. F. Gibb
Keyword(s):  
Stable Isotope ◽  
Hydrothermal Alteration ◽  
Closed System ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Drill Core ◽  
Sr Isotope ◽  
Core Section ◽  
High Silica ◽  
Isotope Measurements

Abstract The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.

scholarly journals Analysis of individual microscopic particles by means of synchrotron radiation induced x-ray micro fluorescence

1992 ◽  
Vol 50 (2) ◽  
pp. 1766-1767
Author(s):  
K. Janssens ◽  
F. Adams ◽  
M.L. Rivers ◽  
K.W. Jones
Keyword(s):  
Synchrotron Radiation ◽  
Detection Limits ◽  
Fluorescence Analysis ◽  
Individual Particle ◽  
Quantitative Character ◽  
Particle Analysis ◽  
X Ray ◽  
Interesting Approach ◽  
Radiation Induced ◽  
Backscattered Electron

Micro-SXRF (Synchrotron X-ray Fluorescence) or micro-SRIXE (Synchrotron Radiation Induced X-ray Emission) is a microanalytical technique which combines the sensitivity of more conventional microchemical methods such as Secondary Ion Microscopy (SIMS) and μ-PIXE (Proton Induced X-ray Emission) with the non-destructive and quantitative character of X-ray fluorescence analysis. The detection limits attainable at current SXRF-facilities are situated in the ppm (and in favourable cases the sub-ppm) range. The sensitivity of SRIXE can be used advantageously in individual particle analysis. This type of analysis is used, e.g., for studying sources of athmospheric pollution. Analysis of standard NIST micro-spheres at the NSLS-SRIXE facility yielded minimum detection limits in the 1 to 100 ppm range for particle sizes of around 10 to 30 μm.An interesting approach to individual particle characterisation is by means of electron microprobe analysis (EPMA). By using the backscattered electron signals, in an automated fashion, particles can be easily located on a filter substrate and their size and shape determined.

The Role of Factor and Regression Analysis in the Interpretation of Geochemical Reconnaissance Data

1975 ◽  
Vol 12 (8) ◽  
pp. 1316-1330 ◽  
Author(s):  
L. G. Closs ◽  
Ian Nichol
Keyword(s):  
Factor Analysis ◽  
Regression Analysis ◽  
Massive Sulfide ◽  
Glacial Till ◽  
Geochemical Data ◽  
Sulfide Mineralization ◽  
Element Data ◽  
Copper And Zinc ◽  
The Individual

The interpretation of exploration oriented geochemical data frequently requires the recognition of subtle features related to mineralization, from the more obvious geochemical expressions of bedrock and surface environments. A number of previous investigations have indicated the potential of various computerized interpretational procedures as aids in identifying these features in geochemical data. The present investigation was concerned with the interpretation of multi-element data from a 750 mile2 {1942.5 km2) area of the Notre Dame Bay district of Newfoundland. The area is underlain by a series of Ordovician and Silurian sediments and volcanics and intrusives overlain by glacial deposits mostly composed of glacial till. Massive sulfide mineralization including the Whalesback and Gullbridge deposits occur within the Ordovician volcanics. R mode factor analysis was employed to establish the character and distribution of the principle metal associations related to bedrock and surface environment contributing to the overall data distribution. The factor scores were regressed against the individual metal concentrations of the elements composing the respective factors, the resulting residuals of the metals reflecting the component of metal related to some sources other than those reflected by the metal associations established by factor analysis. Anomalous areas of residual copper and zinc distributions indicate the areas of known sulfide mineralization more closely than the untreated metal distributions. On this basis, anomalous areas of residual copper and zinc, unrelated to known sulfide mineralization warrant further exploration investigation. It is therefore concluded that a combination of factor and regression analysis on multi-element data from the Notre Dame Bay district of Newfoundland serves to highlight subtle though significant features in multi-element data possibly related to mineralization that were not apparent from a consideration of the untreated data.

Txrf-Sources-Samples and Detectors

1995 ◽  
Vol 39 ◽  
pp. 755-766
Author(s):  
P. Wobrauschek ◽  
P. Kregsamer ◽  
W. Ladisich ◽  
R. Riede ◽  
Christina Streli ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Detection Limits ◽  
Fluorescence Analysis ◽  
Total Reflection ◽  
Light Elements ◽  
X Ray

Total reflection x-ray fluorescence analysis (TXRF) has reached a mature state but still improvements are possible in selecting the proper components for TXRF and optimizing them in the best suitable way. Two approaches are presented, the extension of the number of detectable elements after K-shell excitation and the improvement of the detection limits. The results show, that the elements from B to U can be detected by their characteristic K-lines and that detection limits for medium Z elements e.g. Ni in the fg range are achievable. Most of the best results have been measured using synchrotron radiation with spectral modifying devices like multilayer monochromators. Other x-ray sources like a windowless tube with exchangeable anodes of either material Al, Si or Mo were successfully tested for the efficient excitation of light elements.

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