Fluid Inclusions in Hydrothermal Ore Deposits

Bodnar, Robert J.; Lecumberri-Sánchez, Pilar; Moncada, Daniel; Steele‐MacInnis, Matthew

doi:10.1016/b978-0-08-095975-7.01105-0

Cited by 216 publications

(138 citation statements)

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“…Using these much higher metal concentrations for the ore-forming fluids, the amount of fluid required to form the Pine Point deposit is reduced to a few 10's of km 3 , and it could have formed in a few tens of thousands of years, rather than a few millions of years (Bodnar, 2009). Similarly, recent analyses of fluid inclusions from porphyry copper deposits has revealed copper contents that are 1-2 orders of magnitude higher (summarised in Bodnar et al, 2014) than had been assumed previously, thus requiring much less fluid and/or much shorter times for the mineralising event.…”

Section: History -The Development Of Ideas About Crustal Fluid Composmentioning

confidence: 99%

Fluids in the Continental Crust

Yardley¹,

Bodnar²

2014

GeochemPersp

229

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Section: History -The Development Of Ideas About Crustal Fluid Composmentioning

confidence: 99%

Fluids in the Continental Crust

Yardley¹,

Bodnar²

2014

GeochemPersp

229

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“…Thus, the trapping temperatures for the early stage Ctype fluid inclusions are from 463 to 487 ∘ C. The recalculated trapping pressure is 239 to 347 MPa (Figure 11). In the middle stage, the upper and lower quartiles of total homogenization [84], and this situation is common in orogenic gold deposits (e.g., [85][86][87]). In the Liyuan deposit, minor CH 4 was found in the carbonic phase of the C-type and PC-type FIs in the middle stage.…”

Section: Fluid Immiscibility and Pressure Estimationsmentioning

confidence: 99%

Origin and Evolution of the Ore-Forming Fluids in the Liyuan Gold Deposit, Central North China Craton: Constraints from Fluid Inclusions and H-O-C Isotopic Compositions

Xiong

et al. 2017

Geofluids

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The Liyuan gold deposit is hosted within Archean basement metamorphic rocks and controlled by the NNE-trending faults in the central North China Craton. The ore-forming processes can be divided into three stages (early, middle, and late). Three types of primary fluid inclusions (FIs) are identified in the Liyuan, including pure carbonic, carbonic-aqueous, and aqueous inclusions. The primary FIs of three stages are mainly homogenized at temperatures of 318-408 ∘ C, 201-329 ∘ C, and 136-229 ∘ C, with salinities of 2.1-8.9, 0.5-12.4, and 0.4-6.3 wt.% NaCl equivalent, respectively. The main Au mineralization is related to the middle stage, and water-rock interaction caused rapid precipitation of gold in this stage. The initial ore-forming fluids were likely magmatic water or metamorphic fluid and mixed with meteoric water at later stages. Due to the lack of granite body at the present mining levels, we speculate that it was magmatic water that might have been exsolved from a concealed granite body at greater depth or it was metamorphic fluid that was directly transported from depth via deep faults. Based on all the available geological and geochemical evidence, we suggest that the Liyuan deposit belongs to orogenic gold deposit that located in the interior North China Craton.

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“…Fluid salinity is also intrinsically related to base metal solubility in many fluids (Yardley, 2005) and so is a master variable in metal transport. Finally, fluid salinity can be quite diagnostic of fluid source with the most saline, halite--bearing inclusions being almost exclusively magmatic in origin, saline (but halite--undersaturated) inclusions with elevated CaCl2 being typical of basinal brines, and very low (near zero) salinity inclusions being likely to represent meteoric fluids (Wilkinson, 2001;Bodnar et al, 2014).Despite their importance, salinity determinations in fluid inclusions can be difficult in many samples because of: (i) poor optical resolution in cloudy or semi--transparent minerals (e.g. calcite); (ii) difficulties in resolving final ice melting temperature, particularly in low salinity fluids where the refractive index contrast between fluid and ice is small; or (iii) because of extremely small inclusion size.…”

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“…Total homogenisation temperatures, typically by liquid--vapor homogenisation, can provide minimum constraints on trapping pressure and temperature. Measurements of halite, hydrate and ice melting temperatures can be used to estimate fluid salinity, assuming simple model systems such as NaCl--H2O (Roedder, 1984;Wilkinson, 2001;Bodnar et al, 2014). Multiple solid phase melting temperatures can also be combined to interpret compositions and fluid evolution processes in ternary compositional space, such as NaCl--KCl--H2O or H2O--FeCl2--NaCl in porphyry systems (e.g.…”

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Metastable Freezing: A New Method for the Estimation of Salinity in Aqueous Fluid Inclusions

Wilkinson

2017

Economic Geology

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On cooling during microthermometry, fluid inclusions invariably supercool before freezing under disequilibrium (metastable) conditions to form ice and hydrates. Measurements of fluid inclusions from the Irish Zn--Pb hydrothermal system reveal a strong linear correlation (R 2 = 0.968) between final ice melting temperature (TmI) and metastable freezing temperature (Tmf) of the form: TmI = 0.563 Tmf + 22.7 (+1.5/--3.5) The relationship is shown to be independent of heating--freezing stage model, host mineral, and largely of inclusion size, but is affected by the presence of CO2 and by cooling rate. The correlation shows that metastable freezing is predictable and in fact, in small droplets of pure solution, occurs at a well--defined, salinity--dependent temperature referred to as the homogeneous freezing point. This relationship allows salinity to be estimated in fluid inclusions where the optical recognition of final ice melting is not possible due to small inclusion size or cloudy samples, or where inclusions go into a metastable, vapor--absent, state because of collapse of the bubble on freezing. Using a cooling rate of 50°C/min, inclusion salinity is given by:Salinity (wt% NaCl equivalent) = --69.7 --2.617Tmf --0.02603Tmf 2 --0.0000994Tmf 3 The homogeneous freezing point is controlled by an equilibrium thermodynamic property related to the activity of water. In small droplets of pure solution, as approximated by fluid inclusions, freezing will occur when the water activity is 0.305 above that of the stable ice melting condition at the same temperature, independent of solute type. "Early" metastable freezing, at a temperature above the homogeneous freezing point may occur in very large inclusions, or those containing "seed" particles or CO2. In such cases, the salinity will be underestimated by the equation above. Introduction Fluid inclusion microthermometry has been long established as the only direct method for constraining the properties of paleofluids in the Earth's crust (e.g. Roedder, 1967a). In particular, the ability to constrain fluid density, trapping temperature and pressure, solute and volatile contents has provided many important tests of genetic models for hydrothermal ore formation (Roedder and Bodnar, 1997). It is also the basis for the more advanced techniques such as laser ablation ICP--MS that are providing fundamental new insights into metal transport and deposition from ore--forming fluids (e.g. Audetat et al., 1998Audetat et al., , 2008Heinrich et al., 1999;Ulrich et al., 1999;Wilkinson et al., 2009;Kouzmanov and Pokrovski, 2012).The basic principles of microthermometry by which fluid inclusions are investigated using a heating--freezing stage are well established (e.g. Roedder, 1984;Shepherd et al., 1985). Total homogenisation temperatures, typically by liquid--vapor homogenisation, can provide minimum constraints on trapping pressure and temperature. Measurements of halite, hydrate and ice melting temperatures can be used to estimate fluid salinity, assuming simple model systems...

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Fluid Inclusions in Hydrothermal Ore Deposits

Cited by 216 publications

References 171 publications

Fluids in the Continental Crust

Fluids in the Continental Crust

Origin and Evolution of the Ore-Forming Fluids in the Liyuan Gold Deposit, Central North China Craton: Constraints from Fluid Inclusions and H-O-C Isotopic Compositions

Metastable Freezing: A New Method for the Estimation of Salinity in Aqueous Fluid Inclusions

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