Iron isotope behavior during fluid/rock interaction in K-feldspar alteration zone – A model for pyrite in gold deposits from the Jiaodong Peninsula, East China

Zhu, Zhiyong; Jiang, Shao‐Yong; Mathur, Ryan; Cook, Nigel J.; Yang, Tao; Wang, Meng; Ma, Liang; Ciobanu, Cristiana L.

doi:10.1016/j.gca.2017.10.001

Cited by 60 publications

(20 citation statements)

References 78 publications

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“…For instance, δ 98/95 Mo values are expected to decrease from orebarren alteration regions to an area that is well mineralized (i.e., molybdenite preferentially incorporates light Mo isotopes, producing lower δ 98/95 Mo toward the orebody). Similarly, significant isotope fractionations of Fe, Cu, and Zn are observed during ore-forming processes (Graham et al, 2004;Li et al, 2010;Zhu et al, 2018), and we suggest that their isotopic compositions could also have implications in mineral exploration.…”

Section: A Mineralization Efficiency Perspective On Mo Cyclingsupporting

confidence: 67%

Controlling Mechanisms for Molybdenum Isotope Fractionation in Porphyry Deposits: The Qulong Example

McCoy-West

Zhang

et al. 2019

Economic Geology

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Molybdenite-bearing porphyry deposits are the predominant supplier of molybdenum to industrialized society and one of the main hosts of Mo in the upper continental crust. The Mo isotope compositions (δ98/95Mo, normalized to NIST3134 equals 0‰) of molybdenite show considerable variation (–1.62 to +2.27‰), but the factors controlling this variability remain poorly constrained. This information is critical for underpinning genetic models of porphyry deposits, understanding elemental cycling, and utilizing the δ98/95Mo of marine sediments as a paleoredox proxy. Using the well-characterized Qulong porphyry Cu-Mo deposit (Tibet) as an example, here we discuss how rapid cooling, facilitated by mixing hot magmatic fluid with cold meteoric water, can be a controlling factor on efficient mineralization, and then tackle how fluid evolution regulates molybdenum isotope fractionation. Molybdenites, which preferentially partition isotopically light Mo (Rayleigh fractionation), precipitated from a single fluid will develop a heavier δ98/95Mo composition over time, and this also creates heterogeneous δ98/95Mo between molybdenite grains. Whereas a fluid undergoing multiple episodes of intensive boiling will gradually lose its isotopically heavy Mo to the vapor phase, molybdenites crystallizing successively from the residual liquid will then have lighter δ98/95Mo over time. However, when mineralization efficiency becomes too low, a negligible variation in δ98/95Mo of molybdenite is observed. Given that the mineralization efficiency (i.e., the amount of Mo crystallized as molybdenite from the fluid) rarely reaches 100% and molybdenite favors isotopically light Mo, the presence of a residual fluid with isotopically heavy Mo is inevitable. This residual fluid may then become trapped in alteration halos; hence, δ98/95Mo has the potential to aid in locating the mineralization center (e.g., lighter δ98/95Mo toward the orebody). The residual fluid may also feed surface hydrological systems and eventually impact Mo cycling. Our study highlights that understanding the controls of isotope fractionation is critical to bridge the gap between ore formation and elemental cycling, and that other transition metals (e.g., Cu, Fe, and Zn) may follow similar trajectories.

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Section: A Mineralization Efficiency Perspective On Mo Cyclingsupporting

confidence: 67%

Controlling Mechanisms for Molybdenum Isotope Fractionation in Porphyry Deposits: The Qulong Example

McCoy-West

Zhang

et al. 2019

Economic Geology

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“…The enrichment of heavy sulfur isotopes is diagnostic of submarine exhalative deposits, the sulfur in which is mainly derived from non-bacterial reduction of isotopically heavy marine sulfate [71,72]. Zhu et al [73] suggested that the heavy S isotope signature of both deposit types in Jiaodong indicates that the sulfur was derived from the reduction of marine sulfate. The heavy S isotope compositions originating from the reduction of seawater sulfate have been found in most sediment-hosted orogenic Au deposits, VHMS, and SEDEX Cu-Zn-Pb deposits [73][74][75][76].…”

Section: Fluid Immiscibility In the Main Stagementioning

confidence: 99%

“…Zhu et al [73] suggested that the heavy S isotope signature of both deposit types in Jiaodong indicates that the sulfur was derived from the reduction of marine sulfate. The heavy S isotope compositions originating from the reduction of seawater sulfate have been found in most sediment-hosted orogenic Au deposits, VHMS, and SEDEX Cu-Zn-Pb deposits [73][74][75][76]. However, the wall rocks of the Jiaodong gold deposits, dominated by Mesozoic granite and the Neoarchaean basement rocks, could not supply seawater sulfate, and the possibility of the heavy S isotope being derived from recycled seawater in ore-forming fluids was also ruled out by the H-O isotope compositions [17].…”

Section: Fluid Immiscibility In the Main Stagementioning

confidence: 99%

Origin and Evolution of Ore-Forming Fluid and Gold-Deposition Processes at the Sanshandao Gold Deposit, Jiaodong Peninsula, Eastern China

et al. 2019

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The Early Cretaceous Sanshandao gold deposit, the largest deposit in the Sanshandao-Cangshang goldfield, is located in the northwestern part of the Jiaodong peninsula. It is host to Mesozoic granitoids and is controlled by the north by northeast (NNE) to northeast (NE)-trending Sanshandao-Cangshang fault. Two gold mineralizations were identified in the deposit’s disseminated and stockwork veinlets and quartz–sulfide veins, which are typically enveloped by broad alteration selvages. Based on the cross-cutting relationships and mineralogical and textural characteristics, four stages have been identified for both styles of mineralization: Pyrite–quartz (stage 1), quartz–pyrite (stage 2), quartz–pyrite–base metal–sulfide (stage 3), and quartz–carbonate (stage 4), with gold mainly occurring in stages 2 and 3. Three types of fluid inclusion have been distinguished on the basis of fluid-inclusion assemblages in quartz and calcite from the four stages: Pure CO2 gas (type I), CO2–H2O inclusions (type II), and aqueous inclusions (type III). Early-stage (stage 1) quartz primary inclusions are only type II inclusions, with trapping at 280–400 °C and salinity at 0.35 wt %–10.4 wt % NaCl equivalent. The main mineralizing stages (stages 2 and 3) typically contain primary fluid-inclusion assemblages of all three types, which show similar phase transition temperatures and are trapped between 210 and 320 °C. The late stage (stage 4) quartz and calcite contain only type III aqueous inclusions with trapping temperatures of 150–230 °C. The δ34S values of the hydrothermal sulfides from the main stage range from 7.7‰ to 12.6‰ with an average of 10.15‰. The δ18O values of hydrothermal quartz mainly occur between 9.7‰ and 15.1‰ (mainly 10.7‰–12.5‰, average 12.4‰); calculated fluid δ18O values are from 0.97‰ to 10.79‰ with a median value of 5.5‰. The δDwater values calculated from hydrothermal sericite range from −67‰ to −48‰. Considering the fluid-inclusion compositions, δ18O and δD compositions of ore-forming fluids, and regional geological events, the most likely ultimate potential fluid and metal would have originated from dehydration and desulfidation of the subducting paleo-Pacific slab and the subsequent devolatilization of the enriched mantle wedge. Fluid immiscibility occurred during the main ore-forming stage due to pressure decrease from the early stage (165–200 MPa) to the main stage (90–175 MPa). Followed by the changing physical and chemical conditions, the metallic elements (including Au) in the fluid could no longer exist in the form of complexes and precipitated from the fluid. Water–rock sulfidation and pressure fluctuations, with associated fluid unmixing and other chemical changes, were the two main mechanisms of gold deposition.

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“…Fe (Bilenker et al, 2016;Zhu et al, 2018) , Ni (Liu et al, 2018), Cu (Maher et al, 2011;Markl et al, 2006;Mathur et al, 2013), Zn (Gagnevin et al, 2012;Zhou et al, 2014), Mo ( (Greber et al, 2011;Yao et al, 2016), Ag (Mathur et al, 2018) and Te (Fornadel et al, 2014).…”

Section: Insights Into Causes Of Sn Isotope Fractionation In Oresmentioning

confidence: 99%

Sn-Isotope Fractionation as a Record of Hydrothermal Redox Reactions

Yao

Mathur

Powell

et al. 2018

sam

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Iron isotope behavior during fluid/rock interaction in K-feldspar alteration zone – A model for pyrite in gold deposits from the Jiaodong Peninsula, East China

Cited by 60 publications

References 78 publications

Controlling Mechanisms for Molybdenum Isotope Fractionation in Porphyry Deposits: The Qulong Example

Controlling Mechanisms for Molybdenum Isotope Fractionation in Porphyry Deposits: The Qulong Example

Origin and Evolution of Ore-Forming Fluid and Gold-Deposition Processes at the Sanshandao Gold Deposit, Jiaodong Peninsula, Eastern China

Sn-Isotope Fractionation as a Record of Hydrothermal Redox Reactions

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