scholarly journals Genesis of the Late Cretaceous Longquanzhan Gold Deposit in the Central Tan-Lu Fault Zone, Shandong Province, China: Constraints from Noble Gas and Sulfur Isotopes

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 250
Author(s):  
Chuanpeng Liu ◽  
Wenjie Shi ◽  
Junhao Wei ◽  
Huan Li ◽  
Aiping Feng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Late Cretaceous ◽  
Genetic Model ◽  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Noble Gas ◽  
Gold Deposits ◽  
Shandong Province ◽  
Magma Sources

The Longquanzhan deposit is one of the largest gold deposits in the Yi-Shu fault zone (central section of the Tan-Lu fault zone) in Shandong Province, China. It is an altered-rock type gold deposit in which ore bodies mainly occur at the contact zone between the overlying Cretaceous rocks and the underlying Neoarchean gneissic monzogranite. Shi et al. reported that this deposit formed at 96 ± 2 Ma using pyrite Rb–Sr dating method and represents a new gold mineralization event in the Shandong Province in 2014. In this paper, we present new He–Ar–S isotopic compositions to further decipher the sources of fluids responsible for the Longquanzhan gold mineralization. The results show that the δ34S values of pyrites vary between 0.9‰ and 4.4‰ with an average of 2.3‰. Inclusion-trapped fluids in ore sulfides have 3He/4He and 40Ar/36Ar ratios of 0.14–0.78 Ra and 482–1811, respectively. These isotopic data indicate that the ore fluids are derived from a magmatic source, which is dominated by crustal components with minor mantle contribution. Air-saturated water may be also involved in the hydrothermal system during the magmatic fluids ascending or at the shallow deposit site. We suggest that the crust-mantle mixing signature of the Longquanzhan gold deposit is genetically related to the Late Cretaceous lithospheric thinning along the Tan-Lu fault zone, which triggers constantly uplifting of the asthenosphere surface and persistent ascending of the isotherm plane to form the gold mineralization-related crustal level magma sources. This genetic model can be applied, to some extent, to explain the ore genesis of other deposits near or within the Tan-Lu fault belt.

scholarly journals Source of the Chaoyangzhai Gold Deposit, Southeast Guizhou: Constraints from LA-ICP-MS Zircon U–Pb Dating, Whole-rock Geochemistry and In Situ Sulfur Isotopes

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 235 ◽  
Author(s):  
Hinyuen Tsang ◽  
Jingya Cao ◽  
Xiaoyong Yang
Keyword(s):  
Gold Deposit ◽  
Quartz Vein ◽  
Inductively Coupled Plasma ◽  
Large Scale ◽  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Gold Deposits ◽  
Sulfur Source ◽  
Icp Ms ◽  
Gold Bearing

The Chaoyangzhai gold deposit is one of the newly discovered medium to large scale turbidite-hosted gold deposits in Southeast Guizhou, South China. In this study, laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) zircon U–Pb dating on the tuffaceous- and sandy-slates of Qingshuijiang Formation, Xiajiang Group, and gold-bearing quartz vein yielded similar age distributions, indicating that zircon grains in gold-bearing quartz vein originated from the surrounding tuffaceous- and sandy-slates. In addition, the youngest weighted mean ages of the zircon grains from the tuffaceous- and sandy-slates were 775 ± 13 Ma and 777 ± 16 Ma, respectively, displaying that the tuffaceous- and sandy-slates of the Qingshuijiang Formation were likely deposited in Neoproterozoic. Based on their major and trace element compositions, the tuffaceous- and sandy-slates were sourced from a felsic igneous provenance. The sandy slates have higher contents of Au (mostly ranging from 0.019 to 0.252 ppm), than those of the tuffaceous slates (mostly lower than 0.005 ppm). The δ34SV-CDT values of pyrite and arsenopyrite of the gold-bearing samples range from +8.12‰ to +9.99‰ and from +9.78 to +10.78‰, respectively, indicating that the sulfur source was from the metamorphic rocks. Together with the evidence of similar geochemical patterns between the tuffaceous- and sandy-slates and gold-bearing quartz, it is proposed that the gold might be mainly sourced from sandy slates. The metamorphic devolatilization, which was caused by the Caledonian orogeny (Xuefeng Orogenic Event), resulted in the formation of the ore-forming fluid. Gold was likely deposited in the fractures due to changes of the physico-chemical conditions, leading to the formation of the Chaoyangzhai gold deposit, and the large-scale gold mineralization in Southeast Guizhou.

scholarly journals A NEW GOLD ORE REGION IN TANZANIA

2018 ◽  
pp. 55-59
Author(s):  
V. Mykhailov ◽  
А. Tots
Keyword(s):  
Gold Deposit ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Lake Victoria ◽  
Gold Deposits ◽  
Mobile Belt ◽  
Gold Content ◽  
Gold Ore ◽  
Metallogenic Zone ◽  
The Republic

Tanzania is one of the leading gold mining countries in the world and the discovery of new gold resources on its territory is an actual task. Known gold deposits are concentrated mainly in the northwest of the country, in the metallogenic zone of Lake Victoria, where they are associated with the Archean greenstone belts, and to a lesser extent – in the southwest, in the ore regions of Lupa and Mpanda, confined to the Ubendian Paleoproterozoic mobile belt. With regard to the eastern regions of Tanzania, where the Proterozoic structures of the Uzagaran mobile belt are developed, until recently in this region any significant manifestations of gold mineralization were not known. As a result of our research in the northern part of the Morogoro province of the Republic of Tanzania, a new previously unknown gold deposit Mananila was discovered. It is represented by a large volume, up to 400–450 m long, up to 60–80 m thick, mineralized shear zone over intensely leached and schistosed migmatites, gneisses, amphibolites, penetrated by echelon systems of quartz veins and veinlet, steeply dipping bodies of quartz breccia up to 1.0–1.5 m thick. Gold contents range from 0.61 to 8.11 g/t, the average zone content is 2.5–3.0 g/t. Parallel to the main zone, similar structures are developed on the site, although they are of lower thickness. The forecast resources of the deposit are estimated at 20 tons of gold. 2.8 km to the east from the Mananila field, the recently discovered Mazizi gold deposit is located, and a number of small occurrences of gold are also known in the region. All these objects are located within a large shear zone of the northeastern strike, up to 4–5 km width, over 20 km in length. This serves as the basis for the identification of a new gold ore region in the northern part of the Morogoro province of the United Republic of Tanzania, within the Proterozoic mobile belt of Usagaran, the possible gold content of which has never been previously discussed in geological literature.

NOBLE GASES FINGERPRINT THE SOURCE AND EVOLUTION OF ORE-FORMING FLUIDS OF CARLIN-TYPE GOLD DEPOSITS IN THE GOLDEN TRIANGLE, SOUTH CHINA

2020 ◽  
Vol 115 (2) ◽  
pp. 455-469 ◽  
Author(s):  
Xiao-Ye Jin ◽  
Albert H. Hofstra ◽  
Andrew G. Hunt ◽  
Jian-Zhong Liu ◽  
Wu Yang ◽  
...  
Keyword(s):  
South China ◽  
Genetic Model ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Pore Fluid ◽  
Magmatic Fluid ◽  
Metamorphic Fluid ◽  
Independent Evidence ◽  
Golden Triangle ◽  
Carlin Type Gold Deposits

Abstract Precise constraints on the source and evolution of ore-forming fluids of Carlin-type gold deposits in the Golden Triangle (south China) are of critical importance for a better understanding of the ore genesis and a refined genetic model for gold mineralization. However, constraints on the source of ore fluid components have long been a challenge due to the very fine grained nature of the ore and gangue minerals in the deposits. Here we present He, Ne, and Ar isotope data of fluid inclusion extracts from a variety of ore and gangue minerals (arsenian pyrite, realgar, quartz, calcite, and fluorite) representing the main and late ore stages of three well-characterized major gold deposits (Shuiyindong, Nibao, and Yata) to provide significant new insights into the source and evolution of ore-forming fluids of this important gold province. Measured He isotopes have R/RA ratios ranging from 0.01 to 0.4 that suggest a maximum of 5% mantle helium with an R/RA of 8. The Ne and Ar isotope compositions are broadly comparable to air-saturated water, with a few analyses indicating the presence of an external fluid containing nucleogenic 38Ar and radiogenic 40Ar. Plotted on the 20Ne/4He vs. helium R/RA and 3He/20Ne vs. 4He/20Ne diagrams, the results define two distinct arrays that emanate from a common sedimentary pore fluid or deeply sourced metamorphic fluid end-member containing crustal He. The main ore-stage fluids are interpreted as a mixture of magmatic fluid containing mantle He and sedimentary pore fluid or deeply sourced metamorphic fluid with predominantly crustal He, whereas the late ore-stage fluids are a mixture of sedimentary pore fluid or deeply sourced metamorphic fluid bearing crustal He and shallow meteoric groundwater containing atmospheric He. Results presented here, when combined with independent evidence, support a magmatic origin for the ore-forming fluids. The ascending magmatic fluid mixed with sedimentary pore fluid or deeply sourced metamorphic fluid in the ore stage and subsequently mixed with the meteoric groundwater in the late ore stage, eventually producing the Carlin-type gold deposits in the Golden Triangle.

scholarly journals A Nanoscale Investigation of Carlin-Type Gold Deposits: An Atom-Scale Elemental and Isotopic Perspective

2019 ◽  
Vol 114 (6) ◽  
pp. 1123-1133 ◽  
Author(s):  
Phillip Gopon ◽  
James O. Douglas ◽  
Maria A. Auger ◽  
Lars Hansen ◽  
Jon Wade ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Atom Probe ◽  
Gold Deposits ◽  
Atomic Scale ◽  
Chemical Information ◽  
Arsenian Pyrite ◽  
Turquoise Ridge ◽  
Dispersed Gold ◽  
Carlin Type Gold Deposits

Abstract Carlin-type gold deposits are one of the most important gold mineralization styles in the world. Despite their economic importance and the large volume of work that has been published, there remain crucial questions regarding their metallogenesis. Much of this uncertainty is due to the cryptic nature of the gold occurrence, with gold occurring as dispersed nanoscale inclusions within host pyrite rims that formed on earlier formed barren pyrite cores. The small size of the gold inclusions has made determining their nature within the host sulfides and the mechanisms by which they precipitated from the ore fluids particularly problematic. This study combines high-resolution electron probe microanalysis (EPMA) with atom probe tomography (APT) to constrain whether the gold occurs as nanospheres or is dispersed within the Carlin pyrites. APT offers the unique capability of obtaining major, minor, trace, and isotopic chemical information at near-atomic spatial resolution. We use this capability to investigate the atomic-scale distribution of trace elements within Carlin-type pyrite rims, as well as the relative differences of sulfur isotopes within the rim and core of gold-hosting pyrite. We show that gold within a sample from the Turquoise Ridge deposit (Nevada) occurs within arsenian pyrite overgrowth (rims) that formed on a pyrite core. Furthermore, this As-rich rim does not contain nanonuggets of gold and instead contains dispersed lattice-bound Au within the pyrite crystal structure. The spatial correlation of gold and arsenic within our samples is consistent with increased local arsenic concentrations that enhanced the ability of arsenian pyrite to host dispersed gold (Kusebauch et al., 2019). We hypothesize that point defects in the lattice induced by the addition of arsenic to the pyrite structure facilitate the dissemination of gold. The lack of gold nanospheres in our study is consistent with previous work showing that dispersed gold in arsenian pyrite can occur in concentrations up to ~1:200 (gold/arsenic). We also report a method for determining the sulfur isotope ratios from atom probe data sets of pyrite (±As) that illustrates a relative change between the pyrite core and its Au and arsenian pyrite rim. This spatial variation confirms that the observed pyrite core-rim structure is due to two-stage growth involving a sedimentary or magmatic-hydrothermal core and hydrothermal rim, as opposed to precipitation from an evolving hydrothermal fluid.

scholarly journals Geochemistry, geochronology, and fluid inclusion study of the Late Cretaceous Newton epithermal gold deposit, British Columbia

2016 ◽  
Vol 53 (1) ◽  
pp. 10-33 ◽  
Author(s):  
Lijuan Liu ◽  
Jeremy P. Richards ◽  
S. Andrew DuFrane ◽  
Mark Rebagliati
Keyword(s):  
British Columbia ◽  
Gold Deposit ◽  
Late Cretaceous ◽  
Gold Mineralization ◽  
Volcanic Rocks ◽  
Fluid Inclusion Study ◽  
Epithermal Gold ◽  
Epithermal Gold Deposit ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Newton is an intermediate-sulfidation epithermal gold deposit related to Late Cretaceous continental-arc magmatism in south-central British Columbia. Disseminated gold mineralization occurs in quartz–sericite-altered Late Cretaceous felsic volcanic rocks, and feldspar–quartz–hornblende porphyry and quartz–feldspar porphyry intrusions. The mineralization can be divided into three stages: (1) disseminated pyrite with microscopic gold inclusions, and sparse quartz–pyrite ± molybdenite veins; (2) disseminated marcasite with microscopic gold inclusions and minor base-metal sulfides; and (3) polymetallic veins of pyrite–chalcopyrite–sphalerite–arsenopyrite. Re–Os dating of molybdenite from a stage 1 vein yielded an age of 72.1 ± 0.3 Ma (published by McClenaghan in 2013). The age of the host rocks has been constrained by U–Pb dating of zircon: Late Cretaceous felsic volcanic rocks, 72.1 ± 0.6 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013); feldspar–quartz–hornblende porphyry, 72.1 ± 0.5 Ma; quartz–feldspar porphyry, 70.9 ± 0.5 Ma (Amarc Resources Ltd., unpublished data, reported by McClenaghan in 2013). The mineralized rocks are intruded by a barren diorite, with an age of 69.3 ± 0.4 Ma. Fluid inclusions in quartz–pyrite ± molybdenite ± gold veins yielded an average homogenization temperature of 313 ± 51 °C (number of samples, n = 82) and salinity of 4.8 ± 0.9 wt.% NaCl equiv. (n = 46), suggesting that a relatively hot and saline fluid likely of magmatic origin was responsible for the first stage of mineralization. Some evidence for boiling was also observed in the veins. However, the bulk of the gold mineralization occurs as disseminations in the wall rocks, suggesting that wall-rock reactions were the main control on ore deposition.

scholarly journals Genesis of the Koka Gold Deposit in Northwest Eritrea, NE Africa: Constraints from Fluid Inclusions and C-H-O-S Isotopes

2019 ◽  
Author(s):  
Kai Zhao ◽  
Huazhou Yao ◽  
Jianxiong Wang ◽  
Ghebsha Fitwi Ghebretnsae ◽  
Wenshuai Xiang ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Meteoric Water ◽  
Gold Mineralization ◽  
Early Stage ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Quartz Veins ◽  
Three Phase ◽  
Igneous Origin ◽  
Ne Africa

The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on the paragenetic study two main stages of gold mineralization were identified in the Koka gold deposit: 1) an early stage of pyrite-chalcopyrite-sphalerite-galena-gold-quartz vein; and 2) a second stage of pyrite-quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2-H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268℃, from NaCl-CO2-H2O(-CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water, meteoric water and magmatic water, whereas sulfur isotope suggest an igneous origin. Features of geology and ore-forming fluid at Koka deposit are similar to those of orogenic gold deposits, suggesting the Koka deposit might be an orogenic gold deposit related to granite.

scholarly journals Geochemical studies of the Nanxiaoyao gold deposit in central Yishu fault zone, Shandong province, Eastern China

2020 ◽  
Vol 5 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Ling-qiang Meng ◽  
Guang-zhou Mao ◽  
Xiao-tong Liu ◽  
Peng-rui An ◽  
Ming-ping Cao ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Eastern China ◽  
Shandong Province ◽  
Yishu Fault Zone ◽  
Geochemical Studies

scholarly journals Two Hydrothermal Events at the Shuiyindong Carlin-Type Gold Deposit in Southwestern China: Insight from Sm–Nd Dating of Fluorite and Calcite

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 230 ◽  
Author(s):  
Tan ◽  
Xia ◽  
Xie ◽  
Wang ◽  
Wei ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Lower Triassic ◽  
Gold Deposits ◽  
Upper Permian ◽  
Southwestern China ◽  
Nd Isotope ◽  
T Values ◽  
Isotope Dating ◽  
Total Concentrations

The Shuiyindong Gold Mine hosts one of the largest and highest-grade, strata-bound Carlin-type gold deposits discovered to date in Southwestern China. The outcrop stratigraphy and drill core data of the deposit reveal Middle–Upper Permian and Lower Triassic formations. The ore is mainly hosted in Upper Permian bioclastic limestone near the axis of an anticline. The gold is mainly hosted in arsenian pyrite and arsenopyrite, mainly existing in the form of crystal lattice gold, submicroscopic particles and nanoparticles. Fluorite commonly occurs at the vicinity of an unconformity between the Middle–Upper Permian formations, which is proposed to be the structural conduit that fed the ore fluids. Calcite commonly fills fractures at the periphery of decarbonated rocks, which contain high grade orebodies. This study aimed to verify the occurrence of two distinct hydrothermal events at the Shuiyindong, based on Sm–Nd isotope dating of the fluorite and calcite. For this purpose, rare-earth element (REE) concentrations, Sm/Nd isotope ratios, and Sm–Nd isochron ages of the fluorite and calcite were determined. The fluorite and calcite contain relatively high total concentrations of REE (12.3–25.6 μg/g and 5.71–31.7 μg/g, respectively), exhibit variable Sm/Nd ratios (0.52–1.03 and 0.57–1.71, respectively), and yield Sm–Nd isochron ages of 200.1 ± 8.6 Ma and 150.2 ± 2.2 Ma, with slightly different initial εNd(t) values of −4.4 and −1.1, respectively. These two groups of Sm–Nd isochron ages suggest two episodes of hydrothermal events at the Shuiyindong gold deposit. The age of the calcite probably represents the late stage of the gold mineralization period. The initial εNd(t) values of the fluorite and calcite indicate that the Nd was probably derived from mixtures of basaltic volcanic tuff and bioclastic limestone from the Permian formations.

U-Pb Dating on Hydrothermal Rutile and Monazite from the Badu Gold Deposit Supports an Early Cretaceous Age for Carlin-Type Gold Mineralization in the Youjiang Basin, Southwestern China

2021 ◽  
Author(s):  
Wei Gao ◽  
Ruizhong Hu ◽  
Albert H. Hofstra ◽  
Qiuli Li ◽  
Jingjing Zhu ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Early Cretaceous ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Detrital Zircons ◽  
Youjiang Basin ◽  
Host Rocks ◽  
Gold Bearing ◽  
Carlin Type Gold Deposits

Abstract The Youjiang basin on the southwestern margin of the Yangtze block in southwestern China is the world’s second largest Carlin-type gold province after Nevada, USA. The lack of precise age determinations on gold deposits in this province has hindered understanding of their genesis and relation to the geodynamic setting. Although most Carlin-type gold deposits in the basin are hosted in calcareous sedimentary rocks, ~70% of the ore in the Badu Carlin-type gold deposit is hosted by altered and sulfidized dolerite. Although in most respects Badu is similar to other Carlin-type gold deposits in the province, alteration of the unusual dolerite host produced hydrothermal rutile and monazite that can be dated. Field observations show that gold mineralization is spatially associated with, but temporally later than, dolerite. In situ secondary ion mass spectrometry (SIMS) U-Pb dating on magmatic zircon from the least altered dolerite yielded a robust emplacement age of 212.2 ± 1.9 Ma (2σ, mean square of weighted deviates [MSWD] = 0.55), providing a maximum age constraint on gold mineralization. The U-Th/He ages of detrital zircons from hydrothermally mineralized sedimentary host rocks at Badu and four other Carlin-type gold deposits yielded consistent weighted mean ages of 146 to 130 Ma that record cooling from a temperature over 180° to 200°C and place a lower limit on the age of gold mineralization in the basin. Hydrothermal rutile and monazite that are coeval with gold mineralization have been identified in the mineralized dolerite. Rutile is closely associated with hydrothermal ankerite, sericite, and gold-bearing pyrite. It has high concentrations of W, Fe, V, Cr, and Nb, as well as growth zones that are variably enriched in W, Fe, Nb, and U. Monazite contains primary two-phase fluid inclusions and is intergrown with gold-bearing pyrite and hydrothermal minerals. In situ SIMS U-Pb dating of rutile yielded a Tera-Wasserburg lower intercept age of 141.7 ± 5.8 Ma (2σ, MSWD = 1.04) that is within error of the in situ SIMS Th-Pb age of 143.5 ± 1.4 Ma (2σ, MSWD = 1.5) on monazite. These ages are ~70 m.y. younger than magmatic zircons in the host dolerite and are similar to the aforementioned U-Th/He cooling ages on detrital zircons from hydrothermally mineralized sedimentary host rocks. We, therefore, conclude that the Badu Carlin-type gold deposit formed at ca. 144 Ma. The agreement of the rutile and monazite ages with the U-Th-He cooling ages of Badu and four other Carlin-type gold deposits in the Youjiang basin suggests that ca. 144 Ma is representative of a regional Early Cretaceous Carlin-type hydrothermal event formed during back-arc extension.

Flake-thrust structures and their role in gold deposits formation within Trans-Baikal region

2021 ◽  
pp. 52-61
Author(s):  
Vladimir Salikhov
Keyword(s):  
Gold Deposit ◽  
Significant Role ◽  
Baikal Region ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Low Grade

The significant role of tectonometamorphic gold mineralization style thrust structures in the formation of some gold deposits (Kultuminskoye, Andryushkinskoye, Sepchugur, etc.) within Trans-Baikal region is shown. Thrust structures may present certain prospects for major relatively low-grade gold deposit prospecting, which requires a reassessment of some deposits.

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