The Mina Justa Iron Oxide Copper-Gold (IOCG) Deposit, Peru: Constraints on Metal and Ore Fluid Sources

2021 ◽  
Author(s):  
Maria A. Rodriguez-Mustafa ◽  
Adam C. Simon ◽  
Laura D. Bilenker ◽  
Ilya Bindeman ◽  
Ryan Mathur ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Meteoric Water ◽  
Type I ◽  
Isotopic Data ◽  
Hydrothermal Processes ◽  
Fe Content ◽  
Stable Isotopic ◽  
Copper Gold ◽  
Iocg Deposit ◽  
Mg Content

Abstract Iron oxide copper-gold (IOCG) deposits are major sources of Cu, contain abundant Fe oxides, and may contain Au, Ag, Co, rare earth elements (REEs), U, and other metals as economically important byproducts in some deposits. They form by hydrothermal processes, but the source of the metals and ore fluid(s) is still debated. We investigated the geochemistry of magnetite from the hydrothermal unit and manto orebodies at the Mina Justa IOCG deposit in Peru to assess the source of the iron oxides and their relationship with the economic Cu mineralization. We identified three types of magnetite: magnetite with inclusions (type I) is only found in the manto, is the richest in trace elements, and crystallized between 459° and 707°C; type Dark (D) has no visible inclusions and formed at around 543°C; and type Bright (B) has no inclusions, has the highest Fe content, and formed at around 443°C. Temperatures were estimated using the Mg content in magnetite. Magnetite samples from Mina Justa yielded an average δ56Fe ± 2σ value of 0.28 ± 0.05‰ (n = 9), an average δ18O ± 2σ value of 2.19 ± 0.45‰ (n = 9), and Δ’17O values that range between –0.075 and –0.047‰. Sulfide separates yielded δ65Cu values that range from –0.32 to –0.09‰. The trace element compositions and textures of magnetite, along with temperature estimations for magnetite crystallization, are consistent with the manto magnetite belonging to an iron oxide-apatite (IOA) style mineralization that was overprinted by a younger, structurally controlled IOCG event that formed the hydrothermal unit orebody. Altogether, the stable isotopic data fingerprint a magmatic-hydrothermal source for the ore fluids carrying the Fe and Cu at Mina Justa and preclude significant input from meteoric water and basinal brines.

Fluorite as indicator mineral in iron oxide-copper-gold systems: explaining the IOCG deposit diversity

2020 ◽  
Vol 548 ◽  
pp. 119674
Author(s):  
Tobias U. Schlegel ◽  
Thomas Wagner ◽  
Tobias Fusswinkel
Keyword(s):  
Iron Oxide ◽  
Copper Gold ◽  
Iocg Deposit ◽  
Indicator Mineral

Allanites in the Sin Quyen IOCG deposit, North Vietnam

2020 ◽  
Author(s):  
Chau Nguyen Dinh ◽  
Jadwiga Pieczonka ◽  
Adam Piestrzynski ◽  
Phon Le Khanh ◽  
Hao Duong Van
Keyword(s):  
Optical Properties ◽  
Statistical Analysis ◽  
Iron Oxide ◽  
Chemical Composition ◽  
Major Elements ◽  
Copper Gold ◽  
Crystallization Solution ◽  
Iocg Deposit ◽  
North Vietnam ◽  
Crystallization Stage

Abstract: Allanite minerals are the principal host of REEs in the Sin Quyen, Iron Oxide Copper Gold (IOCG) type deposit. The geochemical characteristics of these minerals are discussed in this work. The studied allanites have an unstable concentration of all major elements, such as REE (14-27 wt%), Ca (9-16 wt%), Al (8-19 wt%), Si (26-34 wt%) and Fe (12-21 wt%). Two different varieties of these minerals are documented, the older with higher REE concentrations ranging from 20 to 27 wt%, and younger with lower total REE concentration ranging from 14 to 19 wt%, which occur as a rim surrounding the older. Differences between the two groups of allanites are documented by Raman spectra and optical properties. The WDS chemical composition indicate that the allanites belong to the Ce-La-ferriallanite family, with low ƩHREE with an average of 0.21 wt.%. This work also supports the estimated timing of the deposit development focusing on detailed petrological study, and documented chemical composition of allanites confirmed by simplified statistical analysis. Temperature 355ºC which was calculated using value of δ34S isotopes is interpreted as a temperature of the second crystallization stage of allanite group. The pressure of crystallization solution was calculated and is ranging from 0.98 to 5.88 MPa.

Iron oxide - copper - gold-type and related deposits in the Manitou Lake area, eastern Grenville Province, Quebec: variations in setting, composition, and style

2005 ◽  
Vol 42 (10) ◽  
pp. 1829-1847 ◽  
Author(s):  
T Clark ◽  
A Gobeil ◽  
J David
Keyword(s):  
Iron Oxide ◽  
Meteoric Water ◽  
Active Faults ◽  
Rare Metal ◽  
Lake Area ◽  
Rare Metals ◽  
Grenville Province ◽  
Copper Gold ◽  
Radioactive Minerals ◽  
Metasomatic Replacement

The Manitou Lake area (Kwyjibo and Lac Marmont sectors), located in Quebec's eastern Grenville Province, contains magnetite-rich deposits with variable morphological, mineralogical, and chemical characteristics. Most Kwyjibo sector deposits are rich in Cu, rare-earth elements (REE), Y, P, F, and Ag and are anomalous in Th, U, Mo, W, Zr, and Au, and Lac Marmont sector deposits are commonly poor in these elements. Deposits occur in or are closely associated with 1175–1168 Ma leucogranite. They contain combinations of magnetite, clinopyroxene, blue–green hornblende, titanite, apatite, fluorite, quartz, biotite, andradite, epidote, albite, hematite, sulfides (chalcopyrite, pyrite, pyrrhotite, molybdenite, sphalerite), ilmenite, allanite, and other REE-bearing minerals. Veins and breccias are common. Most of the magnetite mineralization was preceded by potassic metasomatism (microcline) and was followed by most of the sulfides and radioactive minerals. Nearby sulfide-dominant deposits may be related. The deposits were formed by metasomatic replacement and fracture filling from hydrothermal fluids of variable composition, which were probably channeled in major, active faults. Oxygen-isotope data from magnetite-rich rocks suggest that fluids were predominantly magmatic and (or) metamorphic and that, locally, mixing with cooler meteoric water may have facilitated precipitation of sulfides and rare-metal minerals. Titanites in mineralized rock have been dated at 972 ± 5 Ma, but most magnetite may be older. Mineralization was syn- to post-tectonic and occurred in an orogenic to orogenic-collapse setting. The Cu–REE–Y-rich deposits are similar to iron oxide – copper – gold (IOCG) Olympic Dam type deposits, and copper- and rare-metals-poor occurrences resemble magnetite ± apatite Kiruna-type deposits.

Formation of the Mantoverde iron oxide-copper-gold (IOCG) deposit, Chile: insights from Fe and O stable isotopes and comparisons with iron oxide-apatite (IOA) deposits

2020 ◽  
Vol 55 (7) ◽  
pp. 1489-1504 ◽  
Author(s):  
Tristan M. Childress ◽  
Adam C. Simon ◽  
Martin Reich ◽  
Fernando Barra ◽  
Mauricio Arce ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Iron Oxide ◽  
Copper Gold ◽  
Iocg Deposit

A Continuum from Iron Oxide Copper-Gold to Iron Oxide-Apatite Deposits: Evidence from Fe and O Stable Isotopes and Trace Element Chemistry of Magnetite

2020 ◽  
Vol 115 (7) ◽  
pp. 1443-1459 ◽  
Author(s):  
Maria A. Rodriguez-Mustafa ◽  
Adam C. Simon ◽  
Irene del Real ◽  
John F.H. Thompson ◽  
Laura D. Bilenker ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Stable Isotope ◽  
Trace Element ◽  
Minor Element ◽  
Open Pit ◽  
Temporal Association ◽  
Iocg Deposits ◽  
Copper Gold ◽  
Iocg Deposit ◽  
O Isotope

Abstract Iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of Fe, Cu, and Au. Magnetite is the modally dominant and commodity mineral in IOA deposits, whereas magnetite and hematite are predominant in IOCG deposits, with copper sulfides being the primary commodity minerals. It is generally accepted that IOCG deposits formed by hydrothermal processes, but there is a lack of consensus for the source of the ore fluid(s). There are multiple competing hypotheses for the formation of IOA deposits, with models that range from purely magmatic to purely hydrothermal. In the Chilean iron belt, the spatial and temporal association of IOCG and IOA deposits has led to the hypothesis that IOA and IOCG deposits are genetically connected, where S-Cu-Au–poor magnetite-dominated IOA deposits represent the stratigraphically deeper levels of S-Cu-Au–rich magnetite- and hematite-dominated IOCG deposits. Here we report minor element and Fe and O stable isotope abundances for magnetite and H stable isotope abundances for actinolite from the Candelaria IOCG deposit and Quince IOA prospect in the Chilean iron belt. Backscattered electron imaging reveals textures of igneous and magmatic-hydrothermal affinities and the exsolution of Mn-rich ilmenite from magnetite in Quince and deep levels of Candelaria (>500 m below the bottom of the open pit). Trace element concentrations in magnetite systematically increase with depth in both deposits and decrease from core to rim within magnetite grains in shallow samples from Candelaria. These results are consistent with a cooling trend for magnetite growth from deep to shallow levels in both systems. Iron isotope compositions of magnetite range from δ56Fe values of 0.11 ± 0.07 to 0.16 ± 0.05‰ for Quince and between 0.16 ± 0.03 and 0.42 ± 0.04‰ for Candelaria. Oxygen isotope compositions of magnetite range from δ18O values of 2.65 ± 0.07 to 3.33 ± 0.07‰ for Quince and between 1.16 ± 0.07 and 7.80 ± 0.07‰ for Candelaria. For cogenetic actinolite, δD values range from –41.7 ± 2.10 to –39.0 ± 2.10‰ for Quince and from –93.9 ± 2.10 to –54.0 ± 2.10‰ for Candelaria, and δ18O values range between 5.89 ± 0.23 and 6.02 ± 0.23‰ for Quince and between 7.50 ± 0.23 and 7.69 ± 0.23‰ for Candelaria. The paired Fe and O isotope compositions of magnetite and the H isotope signature of actinolite fingerprint a magmatic source reservoir for ore fluids at Candelaria and Quince. Temperature estimates from O isotope thermometry and Fe# of actinolite (Fe# = [molar Fe]/([molar Fe] + [molar Mg])) are consistent with high-temperature mineralization (600°–860°C). The reintegrated composition of primary Ti-rich magnetite is consistent with igneous magnetite and supports magmatic conditions for the formation of magnetite in the Quince prospect and the deep portion of the Candelaria deposit. The trace element variations and zonation in magnetite from shallower levels of Candelaria are consistent with magnetite growth from a cooling magmatic-hydrothermal fluid. The combined chemical and textural data are consistent with a combined igneous and magmatic-hydrothermal origin for Quince and Candelaria, where the deeper portion of Candelaria corresponds to a transitional phase between the shallower IOCG deposit and a deeper IOA system analogous to the Quince IOA prospect, providing evidence for a continuum between both deposit types.

Kaolinite growth during pore-water mixing: isotopic data from Palaeocene sands, North Sea, UK

Clay Minerals ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 627-636 ◽  
Author(s):  
R. N. T. Stewart ◽  
A. E. Fallick ◽  
R. S. Haszeldine
Keyword(s):  
Pore Water ◽  
North Sea ◽  
Hydrogen Isotope ◽  
Isotope Exchange ◽  
Meteoric Water ◽  
Pore Waters ◽  
Isotopic Data ◽  
Stable Isotopic ◽  
The Witch ◽  
Central North Sea

AbstractStable isotopic and petrographic data have been used to interpret conditions for the formation of authigenic kaolinite within Lower Palaeocene sands, Central North Sea. Two wells within the Witch Ground Graben were sampled (1975 m to 2795 m). Texturally early calcite concretions have isotopic compositions (δ18O = 18.3–21.6‰ SMOW) which indicate that they were precipitated in predominantly meteoric waters. The isotopic composition of later vermiform kaolinite (δ18O = 14.8–17.7‰ SMOW and δD = −53 to −71‰ SMOW) indicates that kaolinite precipitated at around 45–70°C, from a mixed meteoric-marine pore-water (δ18O = −5 to −3‰ SMOW). These modelled precipitation temperatures are consistent with the paragenetic sequence and consequently post-precipitation hydrogen isotope exchange between kaolinite and the pore-waters is presumed not to have occurred. It is inferred that the original depositional marine pore-waters were flushed out during the late Palaeocene (54.8 Ma) by a head of meteoric water from the East Shetland Platform. The Lower Palaeocene aquifer became closed to meteoric influx after marine transgression during the late Palaeocene (54.0 Ma). The remaining meteoric pore-waters in the sandstones became mixed with water from compacting marine muds surrounding the hydrostatically pressured sandstones.

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