Magma dynamics at the base of an evolving mafic magma chamber: Incompatible element evidence from the Partridge River intrusion, Duluth Complex, Minnesota, USA

Chalokwu, Christopher I.; Ariskin, A. A.; Koptev–Dvornikov, E. V.

doi:10.1016/s0016-7037(96)00294-3

Cited by 10 publications

(5 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While this could result from Fe-deficient crystals forming in the simulations compared to the nature, it could also be explained by more effective gravitational accumulation of dense oxides to olivine in nature. In Appendix 1, Figures A2-A4, we provide similar Harker diagrams for FC simulations conducted with three other parental melts suggested for the Duluth Complex (Miller and Weiblen, 1990;Chalokwu et al, 1996;Lee and Ripley, 1996), which show that the parental melt composition used here is generally in better agreement with the natural data.…”

Section: Implications For the Origin Of The Major Rock Types Of The D...mentioning

confidence: 60%

“…The chemistry of the solids and melt in the simulation that we considered the most plausible for the unit IV of the Partridge River intrusion are compared with natural cumulate compositions (see below). Similar comparisons are provided for three other Duluth Complex parental melt compositions (Miller and Weiblen, 1990;Chalokwu et al, 1996;Lee and Ripley, 1996) in Appendix 1.…”

Section: Thermodynamic Modelingmentioning

confidence: 85%

“…Estimating the parental melt compositions for magmatic systems is subject to various uncertainties. For this reason, we have tested a range of H2O contents with the parental melt KEW-6 and three other parental melt compositions (Miller and Weiblen, 1990;Chalokwu et al, 1996;Lee and Ripley, 1996) with initial H2O contents and fO 2 set at 1 wt % and ΔFMQi -2, respectively. These simulations show that, although the parental melt compositions differ considerably for several major element oxides (see App.…”

Section: Uncertainties In the Sulfide Saturation Modelsmentioning

confidence: 99%

“…For the KEW-6 at 200 MPa, the results are shown for FeS sulfide as well. The other parental melts are from Miller and Weiblen (1990;M&W90), Chalokwu et al (1996;C96), and Lee and Ripley (1996;L&R96). (Ripley, 1981;Rao and Ripley, 1983;Tyson and Chang, 1984;Thériault and Barnes, 1998;Ripley et al, 2007).…”

Section: Simulations With Sulfur-bearing Wall Rockmentioning

confidence: 99%

See 3 more Smart Citations

Modeling the sulfide saturation in continuously assimilating magmatic systems with the Magma Chamber Simulator

Virtanen¹,

Heinonen²,

Barber³

et al. 2021

Preprint

View full text Add to dashboard Cite

The timing and degree of immiscible sulfide precipitation in a magma effectively controls the formation of magmatic sulfide deposits and the budget of degassing sulfur species in volcanic systems. Besides the absolute sulfur (S) content, sulfide precipitation is strongly affected by the sulfur content at sulfide saturation (SCSS) in the host silicate melt. Assimilation of S-rich wall-rocks, such as black shales, effectively increases the S content in the magma, while simultaneously lowering the SCSS. Accordingly, assimilation has been identified as the most important process in the formation of many economically significant magmatic base metal sulfide deposit, especially in continental tectonic settings. Detailed understanding of the relation between wall-rock assimilation and sulfide saturation requires accurate thermodynamic models for open magmatic systems experiencing assimilation-fractional crystallization (AFC).The Magma Chamber Simulator (MCS) is currently the only geochemical modeling software that considers the thermodynamic phase equilibria in open magmatic systems involving magma and wall-rock (and recharge) subsystems. We utilized the MCS to explore how assimilation affects the SCSS and S content of the magma. With the current lack of thermodynamic data for sulfides, we tentatively modeled S as a trace element and varied its compatibility to wall-rock in the different models. For a case study, we chose the mafic layered intrusions of Duluth Complex, Minnesota, which host some of the largest Cu-Ni sulfide deposits in the world. Assimilation of the adjacent black shale has been established as the main source for S in the deposits.Our MCS models show in detail how continuous assimilation of the black shale lowers the SCSS of the melt. Partial melt from the black shale enriches the magma in SiO2, Al2O3, K2O, and H2O, while depleting FeO, MgO, CaO, and Na2O, which causes a first order decrease in the SCSS. The compositional change also replaces troctolitic cumulates (plagioclase, olivine &#177; clinopyroxene) with norite (plagioclase and orthopyroxene), which leads to more pronounced FeO depletion in the melt, further lowering the SCSS. On the other hand, the assimilated partial melt also increases the melt mass in the magma subsystem, which counteracts the S enrichment. Accordingly, in the model where S is compatible to the wall-rock residual, the degree of sulfide saturation only slightly increases relative to the same magma experiencing FC without assimilation.More than half of the wall-rock S must partition to the assimilated partial melt in order to meet the S isotopic criteria of the modeled Cu-Ni-deposits. The main stage of sulfide precipitation is associated with ~30 wt.% crystallization of the assimilating host magma. The proportion of sulfides relative to silicates in these models is smaller than observed in the Duluth Complex deposits, which underlines the role of dynamic processes in concentrating sulfides from the silicate magma.

show abstract

Section: Implications For the Origin Of The Major Rock Types Of The D...mentioning

confidence: 60%

Section: Thermodynamic Modelingmentioning

confidence: 85%

Section: Uncertainties In the Sulfide Saturation Modelsmentioning

confidence: 99%

Section: Simulations With Sulfur-bearing Wall Rockmentioning

confidence: 99%

See 2 more Smart Citations

Modeling the sulfide saturation in continuously assimilating magmatic systems with the Magma Chamber Simulator

Virtanen¹,

Heinonen²,

Barber³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…As a rule, instead of an ideal intersection point (for a small number of modelled lines their convergence for each petrogenic oxide can be determined visually) one can see on the T -X diagrams a compact cluster of liquids lines of descent closing on one another in a range of 10-20 • C that corresponds to the accuracy of the COMAGMAT model [Ariskin, 1999]. Our experience in the phase equilibria calculations for dolerites and diabases from differentiated sills [Barmina et al, 1989a[Barmina et al, , 1989bFrenkel et al, 1989;Krivolutskaya et al, 2001], gabbros and troctolites from the Partridge River intrusion [Chalokwu et al, 1993[Chalokwu et al, , 1996 and large layered complexes [Ariskin et al, 2003;Barmina and Ariskin, 2002] has shown that the greater the contrast in compositions that are used, the more accurate the estimates of the trapped (interstitial) liquid temperature and composition that are obtained. This is confirmed by the results obtained for the rocks of the Skaergaard Marginal Border Series (Figure 2).…”

Section: A2 Main Assumptionsmentioning

confidence: 92%

The compositional evolution of differentiated liquids from the Skaergaard Layered Series as determined by geochemical thermometry

Ariskin¹

2003

Russ. J. Earth Sci.

View full text Add to dashboard Cite

Based on the COMAGMAT-3.65 crystallization model a set of phase equilibria calculations (called geochemical thermometry) have been conducted at P =1 kbar and closed conditions with respect to oxygen for 65 rocks representing the principle units of the Layered Series of the Skaergaard intrusion. It allowed us to define the range of initial temperatures (1145 to 1085 • C) and oxygen fugacities (1-1.5 log units above QF M to slightly below QF M) of the original crystal mush from which the rocks from LZa to UZa crystallized. In parallel, average major-element compositions of residual (interstitial) liquid were calculated demonstrating a trend of continual enrichment of FeO * (up to ∼18 wt.%) and TiO 2 (up to ∼5.5 wt.%) with only minor variations in the SiO 2 contents (48 to 50 wt.%). Projection of the compositions onto the OLIV-CP X-QT Z diagram provides evidence that most of the Layered Series crystallized on the Ol-P l-Cpx-oxide cotectic. Systematic differences between the calculated residual liquid compositions for LZa/LZb and LZc to UZa (which are unlikely to reflect fractional crystallization) are within the accuracy of the COMAGMAT model, but may be also indicative of a late-stage process involving migration and re-equilibration of interstitial liquids. Estimated amounts of interstitial melts trapped in the Skaergaard "cumulates" range around 50 wt.%. Wager's compositions inferred from simple mass-balance were found to lie too far from the Ol-P l-Cpx boundary to represent a realistic approximation of the low-pressure Skaergaard magma evolution. The main problem of genetic interpretations of the Skaergaard intrusion is a strong misbalance between the parental compositions followed from contact rocks and the results of geochemical thermometry and that of the whole differentiated body. It is most apparent for TiO 2 and P 2 O 5 which are almost twice as high in the average intrusion composition compared to the proposed parents. Moreover, the intrusion composition has of 2-4 wt.% less SiO 2 and much more iron. One possible explanation is to assume the Skaergaard magma came to the chamber with an amount of crystals (Ol + P l) equilibrated with the calculated parental liquid. However, even if some amount of "hidden" troctolitic material exists, it is unlikely that crystallization in a closed system could produce large volumes of rocks rich in Fe-Ti oxides without complementary more felsic differentiates.

show abstract

Trapped intercumulus liquid in the Main Zone of the eastern Bushveld Complex, South Africa

Lundgaard

Tegner

Cawthorn

et al. 2006

Contrib Mineral Petrol

View full text Add to dashboard Cite

Magma dynamics at the base of an evolving mafic magma chamber: Incompatible element evidence from the Partridge River intrusion, Duluth Complex, Minnesota, USA

Cited by 10 publications

References 29 publications

Modeling the sulfide saturation in continuously assimilating magmatic systems with the Magma Chamber Simulator

Modeling the sulfide saturation in continuously assimilating magmatic systems with the Magma Chamber Simulator

The compositional evolution of differentiated liquids from the Skaergaard Layered Series as determined by geochemical thermometry

Trapped intercumulus liquid in the Main Zone of the eastern Bushveld Complex, South Africa

Contact Info

Product

Resources

About