Lead Isotope Data Research Articles

Lead Isotope Geochemistry of Shales from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon: Implications for Pb Isotope Vectoring in Exhalative Ore Systems

Combined whole-rock lead isotope and high-precision trace element data are reported for shales from the Wolverine deposit and surrounding prospects (e.g., Puck, Fisher, Sable) to elucidate the source of Pb in the shales and their potential utility as an exploration vector. Shales exhibit distinct variations in time-integrated U/Th/Pb evolution with proximity to mineralization. Distal samples resemble the local crustal Pb isotope composition of the northern Cordilleran continental crust (i.e., shale curve). More proximal samples exhibit evidence for hydrothermal activity, but were not significantly mineralized. They have very high U/Th and U/Pb and anomalous present-day 206 Pb/204Pb (>20) coincident with elevated Y/Ho, Zr/Hf, and carbonate alteration. These signatures were derived from oxygenated seawater and imprinted on the shales by oxygenated, CO2-rich hydrothermal fluids that contained uranyl carbonate ions (e.g., UO2(CO3) 3 4– ). It is envisioned that this was due to shallow-level (within 50 m of the seafloor), near-vent ingress of oxygenated seawater associated with hydrothermal venting. A third population of samples is most proximal to mineralization. These, too, have trace element signatures (i.e., high Y/Ho, Zr/Hf, CO2-U enrichment) inherited from seawater, but they do not exhibit anomalous present-day 206Pb/ 204 Pb, being more juvenile in 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208Pb/204Pb. This isotope composition coincides with enrichments in Pb, Zn, Cu, Tl, Sb, W, and Sn (±Cu, Mo). The Pb enrichment associated with mineralization effectively buffered these samples from appreciable Pb isotope evolution, despite overprinting by uranyl carbonate. The juvenile Pb associated with the shales proximal to mineralization argues for deep-penetrative circulation of hydrothermal fluids and leaching of Pb from mafic igneous rocks at depth and/or influence from juvenile magmas at depth (i.e., magmatic fluids). Both of these processes were likely critical for the genesis of mineralization at Wolverine. This study illustrates the utility of quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) for providing sufficiently precise and accurate Pb isotope determinations for district-scale metallogenic evaluations. Furthermore, the coupling of solution ICP-MS Pb isotopes with high-precision trace element geochemistry from the same digest provides a powerful tool for regional exploration studies for hydrothermal mineralization in shale basins.

Hanzhong bronzes and highly radiogenic lead in Shang period China

For decades, the origin of the bronzes with distinct highly radiogenic lead isotopic ratios in Shang period China has been a puzzle. This paper presents new lead isotope data for bronze objects from the Hanzhong region, one of the key regional bronze cultures during Shang period China. On the basis of a synthetical investigation of the typological, chemical and lead isotopic features of Hanzhong bronzes and their relations to other regional bronze cultures, we propose the Qinling area as a potential region of origin for the metals containing highly radiogenic lead used by several contemporaneous but culturally/politically distinct entities across a vast territory. Taking into account both archaeological and geological evidence, this working hypothesis draws attention not merely to the geological provenance of metal resources, but also to the mechanisms of metal production and circulation as well as broader social-economic dynamics.

On the ore provenance of the Trojan silver artefacts

Lead isotopes are a well-established tool to trace the geographic origin of samples and artefacts in archaeology and geochemistry. In archaeology, lead isotopes are often applied to gain information on the provenance of the used ores especially in lead and silver artefacts. The assignment of a specific and unambiguous provenance in most cases is not possible or at least hindered due to several limitations such as ore deposits overlapping in their lead isotopic composition, a large spread within one ore deposit or a missing overlap with known mining sites. Such difficult cases can only be solved by using information from sources being independent of the isotope data. This information can be of chemical nature such as concentrations of key elements or they can be of archaeological nature such as cultural or trade route information. Within this study, we combined lead isotope data of ores and artefacts with silver mass fractions in the ore deposits, Au/Ag-ratios in ores and artefacts and finally archaeological information on the cultural context in the Mediterranean and Anatolian Region. This approach enabled us to significantly reduce the potential number of mining regions. Finally, the potential sources could be narrowed down to the three remaining locations the Central Taurus, Arap Dag and the Eastern Troad. Beneath these three locations, the Central Taurus shows the highest probability for the geographic origin of the galena which has been used to create the Trojan silver artefacts.

The lead ores circulation in Central China during the early Western Han Dynasty: A case study with bronze vessels from the Gejiagou site.

This study first publishes lead isotope data of bronze vessels from Central China in Western Han Dynasty and attempts to find out the lead ores circulation of this time by taking bronzes from the Gejiagou site (Nanyang City, Henan Province) as an example. The elemental concentrations suggest the lead should be introduced on purpose and indicate the provenance information of lead ores. All the lead isotope ratios conform to the characteristics of common lead and most of them are similar to Nanyang local lead ores. The lead of another two bronzes, NY9 and NY13, should be imported from southern China. Combined with the historical background of early Western Han Dynasty, the wider range of the lead ore circulation may be an indicator for, as the loose policy, economic prosperity and transportation improvement.

Hydrothermal copper mineralization in the Mesoproterozoic Huashugou banded iron formation, Northwest China: Characteristics, timing of formation and genesis

Precambrian banded iron formation (BIF)-related copper deposits constitute a rare category in the world with their origins remaining equivocal. Here we investigate the Huashugou Fe-Cu deposit in the North Qilian Orogenic Belt (NQOB), Northwest China, containing approximately 428 Mt iron ore @ 40 wt% Fe and 0.2 Mt Cu (metal) @ 1.82 wt% Cu. The deposit consists of the upper BIF and the lower copper orebodies, which are hosted in the dominantly clastic-carbonate sedimentary Mesoproterozoic Jingtieshan Group. The distribution of the copper orebodies is controlled by NNW-SSE-trending faults. The BIF and phyllite hosted mineralization includes abundant Cu-sulfide minerals distributed along foliation planes, as transgressive veinlets, fissures, and irregular lenses and aggregates, with or without quartz and siderite. Sulfides (chalcopyrite and pyrite) from the copper ores show large variation in δ34S values (−2.7‰ to 32.2‰), which partly overlap with the δ34S values of pyrite and slightly lower than δ34S of barite from the Jingtieshan Group rocks. Most of the sulfides from copper ores have high 207Pb/204Pb and 208Pb/204Pb ratios relative to the country rocks although there are minor overlaps. The lead isotope data show linear correlation between 207Pb/204Pb and 206Pb/204Pb. The sulfur and lead isotope compositions suggest that the ore-forming materials were derived from the host strata. Fluid inclusion studies constrain the trapping temperature of copper mineralization as 180–200 °C, and are related to low salinity (<10.2 wt% NaCl equiv) fluids. The δ18O and δD values of quartz (13.3‰–17.3‰ and −82‰ to −63‰, respectively) and δ13C and δ18O of siderite (−6.7‰ to −4.3‰ and 15.4‰–18.7‰, respectively) intergrown with sulfides, along with the characteristics of the wall rock alteration in the Huashugou area, suggest that strata-sourced ore-forming fluids with a contribution of meteoric water remobilized sulfur and copper from the country rocks. Chalcopyrite from the ores yield Re–Os isotope age of 583.6 ± 7.9 Ma (2σ, MSWD = 1.6), providing tight constraints on the timing of the copper mineralization. We classify the late Neoproterozoic Cu deposit associated with Huashugou BIF as an epigenetic hydrothermal-type deposit.

The Roc Blanc orogenic Pb-Zn-Ag-Au deposit (Morocco): a product of metamorphic dehydration and CO2 devolatilization during exhumation of the Variscan Jebilet massif

The Roc Blanc Pb-Zn-Ag ± Au vein system in the Variscan Central Jebilet massif, Morocco, is confined within the contact metamorphic aureole of S- and I-type calc-alkaline granitic stocks (327 ± 4 to 295 ± 15 Ma) along the Marrakech Shear Zone. Host rocks consist of a succession of greenschist- to amphibolite-facies metasedimentary and metavolcaniclastic rocks of Carboniferous age. The ore mineralogy is predominantly base metal and Ag-bearing sulfides and sulfosalts, intergrown with quartz and carbonates. Late-stage gold mineralization is commonly present as electrum in intimate association with all major generations of sulfide and sulfosalt minerals. Ore-related hydrothermal alteration includes silicification, sericitization, chloritization, and carbonatization. Chlorite and arsenopyrite geothermometry suggest mean temperatures of 364 and 350 °C; respectively. Calculated δ18Ofluid values of 15 to 18‰ are consistent with metamorphic fluid sources, by which the mineralizing fluids were produced during the emplacement of granitic intrusions and subsequent devolatilization of graphitic black shale and interlayered carbonate beds. Lead and strontium isotope data constrain the source of the ore-forming components (i.e., metals and sulfur) to the enclosing host rocks. A decrease in temperature during fluid ascent and subsequent alteration-associated fluid-rock interaction resulted in the deposition of the Pb-Zn-Ag ± Au mineralization in a post-collisional extensional setting.

Moving metals III: Possible origins for copper in Bronze Age Denmark based on lead isotopes and geochemistry

This article presents the results of a comprehensive provenance study based on a combined geochemical-isotopic and archaeological approach, comprising 98 analyses of 97 copper-alloy objects from the Danish Bronze Age. When it comes to the question of the origin of the metal, our interpretations diverge somewhat from earlier established theories about the origin of copper imported to Denmark, which mainly pointed to Central and Eastern Europe. Clear geochronological patterns in the Danish dataset are interpreted as being due to shifts in ore sources; reflecting varying areas of origin as well as the utilization of varying ore types. This again relates to shifting trade networks/suppliers and shifting technological trends. Plausible sources for Danish copper-alloys identified in the current study are ore regions in the British Isles, Alpine ore districts in Italy and Austria, as well as ore regions in the western part of the Mediterranean and to some degree the Slovak Carpathians. The comparison includes hundreds of recently published lead isotope data for ores in Slovakia, the Iberian Peninsula and the Italian and Austrian Alps.

Reply to “Enrichment of Bi-Be-Mo-Cd-Pb-Nb-Ga, REEs and Y in the Permian coals of the Huainan Coalfield, Anhui, China: Discussion”

Precambrian banded iron formation (BIF)-related copper deposits constitute a rare category in the world with their origins remaining equivocal. Here we investigate the Huashugou Fe-Cu deposit in the North Qilian Orogenic Belt (NQOB), Northwest China, containing approximately 428 Mt iron ore @ 40 wt% Fe and 0.2 Mt Cu (metal) @ 1.82 wt% Cu. The deposit consists of the upper BIF and the lower copper orebodies, which are hosted in the dominantly clastic-carbonate sedimentary Mesoproterozoic Jingtieshan Group. The distribution of the copper orebodies is controlled by NNW-SSE-trending faults. The BIF and phyllite hosted mineralization includes abundant Cu-sulfide minerals distributed along foliation planes, as transgressive veinlets, fissures, and irregular lenses and aggregates, with or without quartz and siderite. Sulfides (chalcopyrite and pyrite) from the copper ores show large variation in δ34S values (−2.7‰ to 32.2‰), which partly overlap with the δ34S values of pyrite and slightly lower than δ34S of barite from the Jingtieshan Group rocks. Most of the sulfides from copper ores have high 207Pb/204Pb and 208Pb/204Pb ratios relative to the country rocks although there are minor overlaps. The lead isotope data show linear correlation between 207Pb/204Pb and 206Pb/204Pb. The sulfur and lead isotope compositions suggest that the ore-forming materials were derived from the host strata. Fluid inclusion studies constrain the trapping temperature of copper mineralization as 180–200 °C, and are related to low salinity (<10.2 wt% NaCl equiv) fluids. The δ18O and δD values of quartz (13.3‰–17.3‰ and −82‰ to −63‰, respectively) and δ13C and δ18O of siderite (−6.7‰ to −4.3‰ and 15.4‰–18.7‰, respectively) intergrown with sulfides, along with the characteristics of the wall rock alteration in the Huashugou area, suggest that strata-sourced ore-forming fluids with a contribution of meteoric water remobilized sulfur and copper from the country rocks. Chalcopyrite from the ores yield Re–Os isotope age of 583.6 ± 7.9 Ma (2σ, MSWD = 1.6), providing tight constraints on the timing of the copper mineralization. We classify the late Neoproterozoic Cu deposit associated with Huashugou BIF as an epigenetic hydrothermal-type deposit.

Copper‐base Metallurgy in Metal‐Age Bali: Evidence from Gilimanuk, Manikliyu, Pacung, Pangkung Paruk and Sembiran

The Indonesian Archipelago extends over 5000 km of latitude, from 95°E to 141°E, and hosts some of the world's largest active metal mines. While some fascinating ethnographic and historical sources exist, virtually nothing is known of the country's prehistoric metallurgical traditions. Given Indonesia's scale, this situation cannot be remedied in short order, but with this paper we seek to elucidate some metal production and consumption behaviours on Bali, located around 115°E, during the last centuries of the first millennium bc and the early to middle first millennium ad. The studied early Metal Age assemblage of 27 copper‐base artefacts from the sites of Pacung, Sembiran, Bangkah, Pangkung Paruk, Gilimanuk and Manikliyu includes bangle, bowl, drum, hook, mirror and ornamental typologies, and fragments thereof. Fourteen of the 27 samples were suffering from corrosion, but a strong tendency towards leaded copper alloys (21 of 27) can be distinguished, with some bronzes, a high‐tin bronze and a leaded high‐tin bronze. The high proportion of leaded artefacts mean that lead isotope data cannot be used to identify possible sources of copper, but there is good consistency with Mainland South‐East Asian Iron Age leaded alloy signatures for the bulk of the assemblage, possibly indicating the existence of long‐range (~2000–3000 km one way) exchange systems at the outset of the Island South‐East Asian Metal Age, and perhaps as far as China and India in the case of the mirror and bowl, respectively. Of particular note, the Manikliyu ‘Pejeng’ drum, a stylistically idiosyncratic type known from Bali and Java, and for which there is local production evidence, transpired to be consistent in terms of elemental composition and lead signature with Mainland ‘Dong Son’ drums. This could suggest that Pejeng drums were produced not just from metal imported from the Mainland but with melted down Mainland drums; an intriguing case of local reinterpretation of foreign elite material culture and iconography.

Concerns about Quadrupole ICP-MS Lead Isotopic Data and Interpretations in the Environment and Health Fields.

There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes 208Pb/206Pb and 207Pb/206Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields.

Application of Kernel Density Estimates to Lead Isotope Compositions of Bronzes from Ningxia, North‐West China

The aim of this paper is to apply kernel density estimates (KDEs) to the visualization and interpretation of lead isotope data from bronze assemblages found along the northern border of central China, here designated as the Arc. New lead isotope analyses of 30 leaded tin–bronze artefacts from the Wangdahu cemetery (c.500–300 bc) in the Ningxia Hui Autonomous Region, north‐west China, provide the basis for the discussion. By using multivariate KDEs and the calculated likelihood of the overlap, the present work shows that the Wangdahu objects feature a unique linear array of isotope ratios, representing an important element of overall bronzes from the Arc in the first millennium bc. This characteristic isotope signature is fundamentally different from that of Dajing ores in north‐east China, as well from that of early Qin bronzes in Shaanxi and Gansu provinces. This suggests that a variety of metal resources were utilized by peoples living in the Arc. The KDE approach thus proves effective at presenting and comparing lead isotope data.

The features as a county of Chu State: chemical and metallurgical characteristics of the bronze artifacts from the Bayilu site

Twenty bronze samples from the Bayilu site (Nanyang City, Henan Province) were analyzed and compared to contemporaneous bronze artifacts. This study attempts to find out metallurgical and isotopic characteristics of the Bayilu bronzes. The results suggest the bronze artifacts are Cu-Sn-Pb alloys. Most of the bronzes were cast without secondary processing. Five samples were forged and annealed after casting, and three samples might be annealed and forged. Lead isotope data of the samples display a large range. High amount of Ag and Sb may be a trace elemental signature of the Bayilu bronzes. The major elements, the manufacture process, the lead isotope ratios, and the trace elements all have diversities. Compared to contemporary bronze artifacts, some of the samples show characteristics of the bronzes of Chu State. It indicates Shen County might be involved in the political and economic system of Chu State. It is also possible that some of the Bayilu bronzes are imported from somewhere outside Chu State. Combined with the historical background of Shen County, the diversity of the bronzes may be a signature as a border county.

The origin of lead and sulphur in Tulare ore field, Lece magmatic complex, SE Serbia

Lece magmatic complex in SE Serbia, part of the Serbo-Macedonian Metallogenic Province, is one of the most promising zones for lead, zinc and precious metals for the country. This complex was formed as a result of the post-collisional magmatic activity that lasted from Oligocene to Miocene. This study brings new lead and sulphur isotope data with an aim to constrain the origin of mineralizing fluids and to estimate the temperature of their formation. Galena from the Bakrenjaca locality shows high 207Pb/204Pb values implying that the lead was dominantly derived from the upper continental crustal geochemical reservoir which was probably recycled within the mantle and erupted during Tertiary post-collisional magmatism. Sulfur isotope composition of galena, sphalerite and pyrite show overlapping ?34S values in the range between 0 and 3? indicating a mantle origin of sulphur. Sulfur isotopes were also used to estimate the temperature under which the minerals were deposited forming a complex of veins. The calculated temperature is around 350?C. Since this temperature is too high for epithermal deposits, it is probable that the associated minerals weren?t deposited in isotopic equilibrium and other methods should be conducted for more precise temperature evaluation.

Copper and sulfur isotope ratios in Paleozoic-hosted Mississippi Valley-type mineralization in Wisconsin, USA

We provide the first Cu-isotope data for chalcopyrite in Paleozoic carbonate-hosted Mississippi Valley-type (MVT) mineralization, along with corresponding sulfur isotopes, for eastern Wisconsin, USA. Chalcopyrite in this region occurs mainly as disseminated crystals and is associated with regionally extensive dolomite-hosted subeconomic MVT mineralization on the western edge of the ancestral Michigan Basin. A narrow range in δ65Cu values (0 ± 0.5‰) for chalcopyrite is observed along a large region (125 km) of the western margin of the basin that is consistent with a homogeneous Cu-source in the crust with a δ65Cu composition near 0‰, along with limited redox modification during regional flow or hydrothermal precipitation processes. Cu and S-isotope values, in conjunction with existing lead, strontium, and sulfur isotope data from other sulfide minerals in the region, are consistent with a Precambrian source similar to parts of the Midcontinent Rift System, but distinct from some other Precambrian deposits in the region.

Revisiting lead isotope data in Shang and Western Zhou bronzes

Abstract

Provenancing ancient pigments: Lead isotope analyses of the copper compound of egyptian blue pigments from ancient mediterranean artefacts

While the use of Egyptian blue (EB) as the earliest artificial pigment was common amongst ancient Mediterranean cultures throughout Egypt, Mesopotamia, Greece, and the Roman Empire, little is known about ancient production centres and the sources of raw materials. Variations in lead isotope (LI) ratios can be useful for fingerprinting the geological sources of copper metal, which has the potential to indicate local production or importation. This method is here applied to copper- and silica-rich EB pigments in order to investigate the provenance of the copper component. The investigated EB pigments were sampled from nine ancient artefacts of Egyptian, Etruscan, Canosan, and Roman origin (dating from between the 5th century BCE to the early 1st century CE) that are part of the archaeological collection of the Ny Carlsberg Glyptotek (NCG), Denmark. For the first time, copper isotope analysis was also applied to EB pigments to facilitate future studies of copper isotopes in such materials. Variations in copper isotopes hold the potential to complement lead isotope-based provenance considerations. The lead isotope data (LID) of the investigated EB pigments were compared to reference LID of copper minerals of European, Near and Middle Eastern, and North African ores that have been exploited at a time relevant for the studied EB pigments. In support of (i) a previously postulated scenario where the import of copper for producing EB dominated over the use of local resources (Shortland, 2006) and (ii) consistent with the preference for lead isotope-based exclusion of unlikely sources rather than the determination of certain provenance, copper ore deposits pertaining to Egyptian and Italian LI fields show no significant overlap with the LID of the studied EB pigments. Instead, we propose that copper sourced from various European (Aegean, Balkan, Iberian, Central European) deposits potentially supplied the production of the studied EB pigments. For example, (i) the studied Egyptian EB pigments show no overlap with Egyptian copper, but instead with Aegean sources; (ii) based on the highly variable copper provenance of the studied Etruscan EB pigments, we tentatively propose that this might argue for the importation of copper raw materials and a subsequent local production in Etruria, analogous to previously reported Etruscan glass production; (iii) we propose that Iberian copper was used for local EB production at a time when the known large-scale EB production facilities in the Bay of Naples were already active. While the testimony of ancient trade in EB is a difficult topic to unravel, the potential copper sources involved in producing EB pigments of the few investigated archaeological artefacts suggests that a few (EB) pigment workshops/production centres were highly actively trading raw materials and/or manufactured EB pigments with several different Mediterranean civilizations. Many EB pigment producing workshops and distribution sites may have existed throughout the Mediterranean facilitating a highly complex and diverse network of trade in this widely distributed ancient pigment.

Geochronology, geochemistry, and Sr–Nd–Pb–Hf isotopes of the Zhunsujihua granitoid intrusions associated with the molybdenum deposit, northern Inner Mongolia, China: implications for petrogenesis and tectonic setting

The Zhunsujihua porphyry molybdenum deposit, located in northern Inner Mongolia of China that belongs to Central-Asian Orogenic Belt (CAOB), is the only Mo deposit formed in the late Carboniferous in this area so far. Its mineralization is mainly restricted to the Zhunsujihua granitoid intrusions, which are composed of the main granodiorite (GD) and crosscutting, virtually coeval minor syn-ore leucogranite (LG) and diorite porphyry (DP) dykes. LA-ICP-MS zircon U–Pb dating yields crystallization ages of 300.0 ± 2.0, 299.3 ± 2.0, and 299.0 ± 2.6 Ma for the GD, LG, and DP, respectively. The major and trace element lithogeochemical data show that the GD and LG are metaluminous to weakly peraluminous, high-K calc-alkaline series with I-type granite characteristics, strongly oxidized, with low concentrations of Ba, Nb, Sr, P, and Ti and elevated K and Rb contents, indicating typical arc magmatic features. The LG is a product derived by extensive fractional crystallization of a parental magma similar to the GD as evident from the lower Eu/Eu*, Nb/Ta, Zr/Hf, and T Zr. The moderately altered DP exhibits high concentrations of K, Rb, Cs, LREE, Y, and low Sr/Y, with a positive e Nd (300 Ma), which indicates a mantle or juvenile source associated with an arc setting. The Sr–Nd–Hf isotope data show low I Sr (0.70406–0.70461) and moderate e Nd (300 Ma) (−0.9 to 1.5) for the GD and LG, and relatively high e Hf (300 Ma) values (−3.6 to +11.2) for the GD, suggesting the magma mainly originated from the juvenile lower crust that was derived from depleted mantle, with a minor component of ancient continental crust. Lead isotope data have characteristics of a lower crust source with minor contamination by upper crustal material. Combined with previous research, the Zhunsujihua granitoid intrusions developed in an intracontinental volcanic arc (Uliastai) associated with northward subduction of the Paleo-Asian Ocean plate during late Carboniferous to early Permian; this suggests that the subduction of Paleo Asian Ocean may have continued to late Carboniferous, and the Hengenshan basin is probably closed during the early Permian. Fractional crystallization is the main evolutionary process of the felsic magma, which has played an important role in the Mo mineralization. The coeval DP may have provided additional heat for the extended evolution of the crystallizing felsic magma chamber.

Genesis of the Dianfang breccia-hosted gold deposit, western Henan Province, China: Constraints from geology, geochronology and geochemistry

The Dianfang gold deposit, located in Songxian, western Henan province, China, is one of two breccia-hosted gold deposits in the Xiong’ershan–Waifangshan region. Previous studies suggest that the breccia and host volcanic rocks of the Xiong’er Group formed coevally. The deposit consists of seven vein-type orebodies, occurring within the southern and hanging wall margins of the breccia pipe, as well as in fractures in the rhyolites of the Jidanping Formation, and are structurally controlled by ENE-trending faults. Their mineral assemblage includes K-feldspar, quartz, sericite, chlorite, epidote, carbonate, adularia, and sulfides formed from hydrothermal alteration related to mineralization. Pyrite is the dominant ore mineral, and is associated with minor galena, sphalerite, and chalcopyrite. The trace minerals include magnetite, rutile, cervelleite, matildite, and bismuthinite. Gold occurs as native gold, and electrum inclusions in pyrite, or along microfractures in sulfides and quartz. Four stages of hydrothermal mineralization have been identified: quartz–K-feldspar (I), quartz–pyrite (II), polymetallic sulfide (III), and carbonate–adularia (IV). Zircon U–Pb geochronology of the granitic matrix of the breccia constrains the timing of breccia pipe formation to 145.8Ma, indicating it formed at the end of the Late Jurassic, rather than the Paleoproterozoic, as suggested by previous studies. Hydrothermal sulfides from the main orebody yield a Rb–Sr isochron age of 121.5±1.7Ma, placing gold mineralization at the end of the Early Cretaceous. The sulfur and lead isotope data suggest that the ore-forming materials have a close connection with magmatic fluid. The initial 87Sr/86Sr value of the sulfides is 0.71056±0.00012, suggesting an ancient crustal source, likely the Archean Taihua Group, mixed with a juvenile mantle component. The trace element characteristics of pyrite indicate the mineralizing fluid was magmatic in origin, sourced from a magma derived from the partial melting of the Taihua Complex, and may have been affected by water–rock interaction at high temperatures under reducing conditions. Geological, geochronological, and geochemical data suggest the Dianfang ore deposit is genetically related to a hidden late Mesozoic granite, and forms part of an intrusion-related auriferous system. Gold deposits of similar ages are widespread at the southern margin of the North China Craton, and are coeval with the emplacement of felsic and mafic intrusions, exhumation of a metamorphic core complex, and formation of extensively faulted basins. This suggests that the Dianfang gold deposit formed under conditions of lithospheric extension caused by crustal thinning, and the destruction of the lithosphere mantle beneath the craton during the Late Jurassic to Early Cretaceous.

In the Shadow of Timna? The Mining Region of Wadi Amram New Analytical and Archaeological Aspects

The copper mines of Wadi Amram are located only 10 km north of the prehistoric settlements Tall Hujayrat al-Ghuzlan and Tall al- Magass where there is some evidence of copper metallurgy in the Late Chalcolithic / Early Bronze Age I. These two settlements lay near the Gulf of Aqaba and may have been important nodes for the distribution of copper during this period. Earlier lead isotopic studies demonstrated that copper ores from the mines of Timna and Faynan are possible sources for the early copper production, but up until now the much closer copper deposit of Wadi Amram has been ignored. New lead isotope data has shown that the Wadi Amram copper ore can be distinguished from the ore from Timna and closely correlates to the Faynan copper ores. Some of the copper-related objects from Tall Hujayrat al-Ghuzlan and Tall al-Magass have lead isotope ratios more comparable to ore from Wadi Amram than from Timna and warrants a reassessment of the organization mode of the prehistoric mining industry in the southern Levant.

Origin and evolution of ore-forming fluids, and genesis of the Duhuangling and Jiusangou gold deposits in eastern Yanbian, northeast China

The Duhuangling and Jiusangou gold deposits are located east of the Yanbian area, northeast China. We present the results of systematic studies of the ore geology, fluid inclusion (FI) features, and isotopic geochemistry of the two gold deposits. Four mineralization stages have been defined in each gold deposit: pyrite + sericite + quartz (stage I), quartz + pyrite ± chalcopyrite ± arsenopyrite (stage II), quartz + native gold + polymetallic sulfide (stage III), and quartz–calcite (stage IV). FIs from the two gold deposits are similar and contain five types: pure vapor phase (V-type), vapor-rich phase (RV-type), liquid-rich phase (RL-type), daughter mineral-bearing polyphase (S-type), and pure liquid phase (L-type). Stage I FIs homogenize at temperatures of 350–450 °C, yielding salinities of 5.40–48.67 wt.%. FIs from both stages II and III samples homogenize at 160–350 °C, yielding salinities of 5.71–39.75 wt.%. FIs in pyrite from the stage II have 3He/4He ratios of 0.0069–0.0148 Ra and 40Ar/36Ar ratios of 1302–4433, demonstrating that ore-forming fluids of the two gold deposits were derived from the crust. The δD values of the two gold deposits range from −107‰ to −92‰, with δ18OH2O values from 4.3‰ to 9.0‰, indicating that the ore-forming fluids were mainly magmatic water in origin. Lead isotope data suggest that the ore-forming materials were originated from deep crust. Integrated data indicate that both Duhuangling and Jiusangou gold deposits are medium- to high-temperature, hydrothermal gold deposits.