Element mobility and alteration types in Iron Oxide Copper and Gold (IOCG) systems

2020 ◽  
Author(s):  
Jonathan Hamisi ◽  
Iain Pitcairn ◽  
Andrew Tomkins ◽  
Joel Brugger ◽  
Steve Micklethwaite
Keyword(s):  
Mass Balance ◽  
Source Rocks ◽  
Contact Metamorphism ◽  
Mass Change ◽  
Copper Production ◽  
Element Mobility ◽  
Mass Variation ◽  
Potassic Alteration ◽  
Iocg Deposits ◽  
Metamorphic Terranes

<p>IOCG deposits are economically important providing amongst other resources, around 12% of global copper production and 47% of Australian copper production. A number of different genetic models have been proposed for the formation of IOCG deposits including ore systems for which fluids and metals are sourced from igneous bodies (Hauck, 1990; Groves and Vielreicher, 2001; Pollard, 2001) and others where mineralising fluids are non-magmatic. There are two main non-magmatic models. The first suggests that the key heat source is igneous and contact metamorphism drives thermal convection and development of metal rich brines with possible input of metals from the igneous bodies themselves (Haynes et al., 1995; Barton and Johnson, 1996, 2000; Haynes, 2000). The second non-magmatic model suggests that hypersaline brines are produced by metamorphic reactions at depth and the resulting metamorphic brines become metal rich through wall rock interaction as they migrate and possibly mixing with other aqueous phase to form a deposit (Williams, 1994; de Jong et al., 1997; Hitzman, 2000).</p><p>A number of alteration type occurrs in IOCG systems including albitization, scapolitization, “red-rock” alteration (calc-sodic), carbonate alteration, potassic alteration, chlorite alteration as described by Barton (2013). Yet the fundamental relationship between the alteration, the mobility of chemical elements and the formation of the deposits is not well known. <br>We assess metal mobility during different styles of alteration using a mass balance approach comparing suites of well characterised altered rocks of different types to their least altered parent rocks. We aim to identify which styles of alteration can be shown to mobilise metals and therefore constrain potential sources of metals for IOCG ore deposits in metamorphic terranes, with a focus on Olympic and Mt Isa Provinces in Australia.</p><p>Preliminary results of mass balance calculations from the Olympic Province show that potential altered source rocks are significantly depleted in Cu relative to their least altered protoliths. The median Cu and Au mass variation values of rocks albitised at variable degrees (Na alteration) are respectively -87% (range -93% to +258%, n=7) and -27% (range -76% to +69%, n = 7) Similarly rocks with variable potassic alteration (K) have a median Cu mass variation of -52% (range -52% to +186%, n=6) and rocks affected by calc-sodic alteration have Au mass change median of -36% (range -36% to +1656%, n = 10). Mass change in the altered rocks is highly variable with both enrichment and depletion occurring within the same alteration styles. Samples affected by carbonate and potassic alteration are enriched in Au, and calc-sodic and carbonate altered rocks are enriched in Cu. Availability of the particular element in the source rock and lithology play presumably a role in these changes of behaviour in element mobility. </p>

scholarly journals A Joint Inversion Estimate of Antarctic Ice Sheet Mass Balance Using Multi-Geodetic Data Sets

2019 ◽  
Vol 11 (6) ◽  
pp. 653 ◽  
Author(s):  
Chunchun Gao ◽  
Yang Lu ◽  
Zizhan Zhang ◽  
Hongling Shi
Keyword(s):  
Mass Balance ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Mass Change ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
Uplift Rates ◽  
The Antarctic

Many recent mass balance estimates using the Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry (including two kinds of sensors of radar and laser) show that the ice mass of the Antarctic ice sheet (AIS) is in overall decline. However, there are still large differences among previously published estimates of the total mass change, even in the same observed periods. The considerable error sources mainly arise from the forward models (e.g., glacial isostatic adjustment [GIA] and firn compaction) that may be uncertain but indispensable to simulate some processes not directly measured or obtained by these observations. To minimize the use of these forward models, we estimate the mass change of ice sheet and present-day GIA using multi-geodetic observations, including GRACE and Ice, Cloud and land Elevation Satellite (ICESat), as well as Global Positioning System (GPS), by an improved method of joint inversion estimate (JIE), which enables us to solve simultaneously for the Antarctic GIA and ice mass trends. The GIA uplift rates generated from our JIE method show a good agreement with the elastic-corrected GPS uplift rates, and the total GIA-induced mass change estimate for the AIS is 54 ± 27 Gt/yr, which is in line with many recent GPS calibrated GIA estimates. Our GIA result displays the presence of significant uplift rates in the Amundsen Sea Embayment of West Antarctica, where strong uplift has been observed by GPS. Over the period February 2003 to October 2009, the entire AIS changed in mass by −84 ± 31 Gt/yr (West Antarctica: −69 ± 24, East Antarctica: 12 ± 16 and the Antarctic Peninsula: −27 ± 8), greater than the GRACE-only estimates obtained from three Mascon solutions (CSR: −50 ± 30, JPL: −71 ± 30, and GSFC: −51 ± 33 Gt/yr) for the same period. This may imply that single GRACE data tend to underestimate ice mass loss due to the signal leakage and attenuation errors of ice discharge are often worse than that of surface mass balance over the AIS.

scholarly journals Complex principal component analysis of mass balance changes on the Qinghai–Tibetan Plateau

2017 ◽  
Vol 11 (3) ◽  
pp. 1487-1499 ◽  
Author(s):  
Jingang Zhan ◽  
Hongling Shi ◽  
Yong Wang ◽  
Yixin Yao
Keyword(s):  
Tibetan Plateau ◽  
Mass Balance ◽  
Correlation Coefficient ◽  
El Niño ◽  
El Nino ◽  
Principal Component ◽  
Mass Change ◽  
Eastern Himalayas ◽  
The Third ◽  
Northwestern India

Abstract. Climatic time series for Qinghai–Tibetan Plateau locations are rare. Although glacier shrinkage is well described, the relationship between mass balance and climatic variation is less clear. We studied the effect of climate changes on mass balance by analyzing the complex principal components of mass changes during 2003–2015 using Gravity Recovery and Climate Experiment satellite data. Mass change in the eastern Himalayas, Karakoram, Pamirs, and northwestern India was most sensitive to variation in the first principal component, which explained 54 % of the change. Correlation analysis showed that the first principal component is related to the Indian monsoon and the correlation coefficient is 0.83. Mass change on the eastern Qinghai plateau, eastern Himalayas–Qiangtang Plateau–Pamirs area and northwestern India was most sensitive to variation of the second major factor, which explained 16 % of the variation. The second major component is associated with El Niño; the correlation coefficient was 0.30 and this exceeded the 95 % confidence interval of 0.17. Mass change on the western and northwestern Qinghai–Tibetan Plateau was most sensitive to the variation of its third major component, responsible for 6 % of mass balance change. The third component may be associated with climate change from the westerlies and La Niña. The third component and El Niño have similar signals of 6.5 year periods and opposite phases. We conclude that El Niño now has the second largest effect on mass balance change of this region, which differs from the traditional view that the westerlies are the second largest factor.

Seeing through the dolerite-seismic imaging of petroleum systems, Tasmania, Australia

2015 ◽  
Vol 55 (1) ◽  
pp. 297
Author(s):  
Malcolm Bendall ◽  
Clive Burrett ◽  
Paul Heath ◽  
Andrew Stacey ◽  
Enzo Zappaterra
Keyword(s):  
Seismic Energy ◽  
Petroleum System ◽  
Source Rocks ◽  
Contact Metamorphism ◽  
Seismic Surveys ◽  
Reservoir Rocks ◽  
Petroleum Systems ◽  
Potential Reservoir ◽  
Frequency Sweeps ◽  
The Many

Prior to the onshore work of Empire Energy Corporation International (Empire) it was widely believed that the widespread sheets (>650 m thick) of Jurassic dolerite (diabase) would not only have destroyed the many potential petroleum source and reservoir rocks in the basin but would also absorb seismic energy and would be impossible to drill. By using innovative acquisition parameters, however, major and minor structures and formations can be identified on the 1,149 km of 2D Vibroseis. Four Vibroseis trucks were used with a frequency range of 6–140 Hz with full frequency sweeps close together, thereby achieving maximum input and return signal. Potential reservoir and source rocks may be seismically mapped within the Gondwanan Petroleum System (GPS) of the Carboniferous to Triassic Parmeener Supergroup in the Tasmania Basin. Evidence for a working GPS is from a seep of migrated, Tasmanite-sourced, heavy crude oil in fractured dolerite and an oil-bearing breached reservoir in Permian siliciclastics. Empire’s wells show that each dolerite sheet consists of several intrusive units and that contact metamorphism is usually restricted to within 70 m of the sheets’ lower margins. In places, there are two thick sheets, as on Bruny Island. One near-continuous 6,500 km2 sheet is mapped seismically across central Tasmania and is expected, along with widespread Permian mudstones, to have acted as an excellent regional seal. The highly irregular pre-Parmeener unconformity can be mapped across Tasmania and large anticlines (Bellevue and Thunderbolt prospects and Derwent Bridge Anticline) and probable reefs can be seismically mapped beneath this unconformity within the Ordovician Larapintine Petroleum System. Two independent calculations of mean undiscovered potential (or prospective) resources in structures defined so far by Empire’s seismic surveys are 596.9 MMBOE (millions of barrels of oil equivalent) and 668.8 MMBOE.

scholarly journals Response of Antarctic Ice Sheet Mass Balance to Climate Change

2018 ◽  
Author(s):  
Jingang Zhan ◽  
Hongling Shi ◽  
Yong Wang ◽  
Yixin Yao ◽  
Yongbin Wu
Keyword(s):  
Surface Temperature ◽  
Mass Balance ◽  
Ice Sheet ◽  
Low Frequency ◽  
Principal Component ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Mass Change ◽  
Antarctic Ice Sheet ◽  
The Antarctic

Abstract. The ice record should have recorded and will likely reflect information on environmental changes such as atmospheric circulation. In this paper, 153 months of Gravity Recovery and Climate Experiment (GRACE) satellite time-varying gravity solutions were used to study the principal components of the Antarctic ice sheet mass change and their time-frequency variation. This assessment is based on complex principal component analysis and the wavelet amplitude-period spectrum method to reveal the main climatic factors that affect the change on the ice sheet. The complex principal component analysis results reveal the principal components that affect the mass change of the ice sheet; the wavelet analysis present the time-frequency variation of each component and the possible relationship between each principal component and different climatic factors. The results show that the specific climate factors represented by low-frequency signals with a period greater than 5 years dominate the changes of the Antarctic ice sheet mass balance. These climate factors are related to the abnormal sea surface temperature changes in the equatorial Pacific (Niño 1+2 region), the correlation between the low-frequency periodic signal of sea surface temperature anomalies in the equatorial Pacific and the first principal component of the ice sheet mass change in Antarctica is 0.65. The first principal component explains 85.45 % of the mass change in the ice sheet. The change in the meridional wind at 700 hPa in the South Pacific may be the key factor that determines the effect of sea surface temperature anomalies in the equatorial Pacific on the Antarctic ice sheet. The atmospheric temperature change in Antarctica is the second most important factor that affects the mass balance of the ice sheet in the area, and its contribution to the mass balance of the ice sheet is only 6.35 %. This result means that with the increase of low-frequency signals during the El Niño period, Antarctic ice sheet mass changes may intensify.

scholarly journals Density assumptions for converting geodetic glacier volume change to mass change

2013 ◽  
Vol 7 (1) ◽  
pp. 219-244 ◽  
Author(s):  
M. Huss
Keyword(s):  
Mass Balance ◽  
Volume Change ◽  
Conversion Factor ◽  
Constant Factor ◽  
Mass Change ◽  
Mountain Glaciers ◽  
Digital Elevation ◽  
Wide Range ◽  
Density Assumption ◽  
Short Time

Abstract. The geodetic method is widely used for assessing changes in the mass balance of mountain glaciers. However, comparison of repeated digital elevation models only provides a glacier volume change that must be converted to a change in mass using a density assumption. This study investigates this conversion factor based on a firn compaction model applied to simplified glacier geometries with idealized climate forcing, and two glaciers with long-term mass balance series. It is shown that the "density" of geodetic volume change is not a constant factor and is systematically smaller than ice density in most cases. This is explained by the accretion/removal of low-density firn layers, and changes in the firn density profile with positive/negative mass balance. Assuming a value of 850 ± 60 kg m−3 to convert volume change to mass change is appropriate for a wide range of conditions. For short time intervals (≤3 yr), periods with limited volume change, and/or changing mass balance gradients, the conversion factor can however vary from 0–2000 kg m−3 and beyond which requires caution when interpreting glacier mass changes based on geodetic surveys.

scholarly journals Sensitivity of inverse glacial isostatic adjustment estimates over Antarctica

2020 ◽  
Vol 14 (1) ◽  
pp. 349-366
Author(s):  
Matthias O. Willen ◽  
Martin Horwath ◽  
Ludwig Schröder ◽  
Andreas Groh ◽  
Stefan R. M. Ligtenberg ◽  
...  
Keyword(s):  
Mass Balance ◽  
Bias Correction ◽  
Total Mass ◽  
Process Models ◽  
Mass Change ◽  
Quality Data ◽  
Data Sets ◽  
Glacial Isostatic Adjustment ◽  
Satellite Gravimetry ◽  
Isostatic Adjustment

Abstract. Glacial isostatic adjustment (GIA) is a major source of uncertainty for ice and ocean mass balance estimates derived from satellite gravimetry. In Antarctica the gravimetric effect of cryospheric mass change and GIA are of the same order of magnitude. Inverse estimates from geodetic observations hold some promise for mass signal separation. Here, we investigate the combination of satellite gravimetry and altimetry and demonstrate that the choice of input data sets and processing methods will influence the resultant GIA inverse estimate. This includes the combination that spans the full GRACE record (April 2002–August 2016). Additionally, we show the variations that arise from combining the actual time series of the differing data sets. Using the inferred trends, we assess the spread of GIA solutions owing to (1) the choice of different degree-1 and C20 products, (2) viable candidate surface-elevation-change products derived from different altimetry missions corresponding to different time intervals, and (3) the uncertainties associated with firn process models. Decomposing the total-mass signal into the ice mass and the GIA components is strongly dependent on properly correcting for an apparent bias in regions of small signal. Here our ab initio solutions force the mean GIA and GRACE trend over the low precipitation zone of East Antarctica to be zero. Without applying this bias correction, the overall spread of total-mass change and GIA-related mass change using differing degree-1 and C20 products is 68 and 72 Gt a−1, respectively, for the same time period (March 2003–October 2009). The bias correction method collapses this spread to 6 and 5 Gt a−1, respectively. We characterize the firn process model uncertainty empirically by analysing differences between two alternative surface mass balance products. The differences propagate to a 10 Gt a−1 spread in debiased GIA-related mass change estimates. The choice of the altimetry product poses the largest uncertainty on debiased mass change estimates. The spread of debiased GIA-related mass change amounts to 15 Gt a−1 for the period from March 2003 to October 2009. We found a spread of 49 Gt a−1 comparing results for the periods April 2002–August 2016 and July 2010–August 2016. Our findings point out limitations associated with data quality, data processing, and correction for apparent biases.

scholarly journals Effect of Area Distribution with Altitude on Glacier Mass Balance – A Comparison of North and South Klawatti Glaciers, Washington State, U.S.A.

1990 ◽  
Vol 14 ◽  
pp. 278-282 ◽  
Author(s):  
Wendell V. Tangborn ◽  
Andrew G. Fountain ◽  
William G. Sikonia
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
Quadratic Equation ◽  
Washington State ◽  
Mass Change ◽  
Glacier Mass Balance ◽  
The North ◽  
Calculated Mass ◽  
Longitudinal Profiles ◽  
North And South

The North and South Klawatti glaciers are adjacent glaciers in the North Cascade Mountains of Washington state. During 1947–61 North Klawatti Glacier lost volume, equivalent to a mean decrease in thickness of 8.3 m over the glacier area, whereas South Klawatti Glacier gained volume, equivalent to an increase in thickness of 5.8 m. Although the glaciers are in the same climate, they have different distributions of area with altitude, resulting in different responses to climatic variations.A quadratic equation is assumed to approximate the relation of mass balance to altitude for both Klawatti glaciers. The coefficients of the equation are derived by comparing the calculated mass change to the mass change for each glacier estimated from topographic maps. The resultant relation of mass balance to altitude is the mean for the time period between maps (1947–61).Steady-state longitudinal profiles of both glaciers were obtained by shifting the existing mass-balance versus altitude curve by a magnitude equal to the measured mean annual mass balance. To produce steady-state conditions, the equilibrium-line altitudes of both glaciers would need to move less than 90 m (85 m higher for South Klawatti Glacier and 88 m lower for North Klawatti Glacier).

Glacier Changes in Iceland From ∼1890 to 2019

2021 ◽  
Author(s):  
Guðfinna Aðalgeirsdóttir ◽  
Eyjólfur Magnússon ◽  
Finnur Pálsson ◽  
Thorsteinn Thorsteinsson ◽  
Joaquín Belart ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Sea Level ◽  
Total Mass ◽  
Ice Age ◽  
Mass Change ◽  
Negative Mass ◽  
Data Set ◽  
Uncertainty Range ◽  
Loss Rates

<p>The volume of glaciers in Iceland (∼3,400 km<sup>3</sup> in 2019) corresponds to about 9 mm of potential global sea level rise. In this study, observations from 98.7% of glacier covered areas in Iceland (in 2019) are used to construct a record of mass change of Icelandic glaciers since the end of the 19th century i.e. the end of the Little Ice Age (LIA) in Iceland. Glaciological (in situ) mass-balance measurements have been conducted on Vatnajökull, Langjökull, and Hofsjökull since the glaciological years 1991/92, 1996/97, and 1987/88, respectively. The combined record shows a total mass change of −540 ± 130 Gt (−4.2 ± 1.0 Gt a−1 on average) during the study period (1890/91 to 2018/19). This mass loss corresponds to 1.50 ± 0.36 mm sea level equivalent or 16 ± 4% of mass stored in Icelandic glaciers around 1890. Almost half of the total mass change occurred in 1994/95 to 2018/19, or −240 ± 20 Gt (−9.6 ± 0.8 Gt a−1 on average), with most rapid loss in 1994/95 to 2009/10 (mass change rate −11.6 ± 0.8 Gt a−1). During the relatively warm period 1930/31–1949/50, mass loss rates were probably close to those observed since 1994, and in the colder period 1980/81–1993/94, the glaciers gained mass at a rate of 1.5 ± 1.0 Gt a−1. For other periods of this study, the glaciers were either close to equilibrium or experienced mild loss rates. Comparison of our results with WGMS time series (Zemp et al., 2019) shows that the interannual variability is generally well captured by both data sets, but some details are not; for example, the large ice melt due to the Gjálp eruption in October 1996 and the non-surface mass balance are not included by WGMS data set. Our time seris is within the large uncertainty range of the GRACE record (Wouters et al., 2019) that has some years (e.g., 2006/07 and 2010/11) with more negative mass change, and others (e.g., 2005/06, 2011/12, and 2013/14) with less negative mass change than our estimates.</p>

scholarly journals Runaway thinning of the low-elevation Yakutat Glacier, Alaska, and its sensitivity to climate change

2015 ◽  
Vol 61 (225) ◽  
pp. 65-75 ◽  
Author(s):  
Barbara L. Trüssel ◽  
Martin Truffer ◽  
Regine Hock ◽  
Roman J. Motyka ◽  
Matthias Huss ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Mass Change ◽  
Balance Model ◽  
Surface Mass Balance ◽  
Elevation Change ◽  
Southeast Alaska ◽  
Surface Mass ◽  
Climate Conditions ◽  
Decadal Scale

AbstractLake-calving Yakutat Glacier in southeast Alaska, USA, is undergoing rapid thinning and terminus retreat. We use a simplified glacier model to evaluate its future mass loss. In a first step we compute glacier-wide mass change with a surface mass-balance model, and add a mass loss component due to ice flux through the calving front. We then use an empirical elevation change curve to adjust for surface elevation change of the glacier and finally use a flotation criterion to account for terminus retreat due to frontal ablation. Surface mass balance is computed on a daily timescale; elevation change and retreat is adjusted on a decadal scale. We use two scenarios to simulate future mass change: (1) keeping the current (2000–10) climate and (2) forcing the model with a projected warming climate. We find that the glacier will disappear in the decade before 2110 or 2070 under constant or warming climates, respectively. For the first few decades, the glacier can maintain its current thinning rates by retreating and associated loss of high-ablating, low-elevation areas. However, once higher elevations have thinned substantially, the glacier can no longer counteract accelerated thinning by retreat and mass loss accelerates, even under constant climate conditions. We find that it would take a substantial cooling of 1.5°C to reverse the ongoing retreat. It is therefore likely that Yakutat Glacier will continue its retreat at an accelerating rate and disappear entirely.

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