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Mafic intrusions on the NE shoulder of the Midcontinent Rift (Keweenawan LIP), including Cu–PGE mineralized gabbros within the Coldwell Complex (CC), and rift parallel or radial dykes outside the CC are correlated based on characteristic trace element patterns. In the Coldwell Complex, mafic rocks are subdivided into four groups: (1) early metabasalt; (2) Marathon Series; (3) Layered Series; (4) Geordie–Wolfcamp Series. The Marathon Series are correlated with the rift radial Abitibi dykes (1140 Ma), and the Geordie–Wolfcamp Series with the rift parallel Pukaskwa and Copper Island dykes. U–Pb ages determined for five gabbros from the Layered and Marathon Series are between 1107·7 and 1106·0 Ma. Radiogenic isotope ratios show near chondritic (CHUR) εNd(1106 Ma) and 87Sr/86Sri values that range from –0·38 to +1·13 and 0·702537 to 0·703944, respectively. Distinctive geochemical properties of the Marathon Series and Abitibi dykes, such as Ba/La (14–37), Th/Nb (0·06–0·12), La/Sm (3·8–7·7), Sr/Nd (21–96) and Zr/Sm (9–19), are very different from those of the Geordie–Wolfcamp Series and a subset of Copper Island and Pukaskwa dykes with Ba/La (8·7–11), Th/Nb (0·12–0·13), La/Sm (6·7–7·9), Sr/Nd (5–7·8) and Zr/Sm (18–24). Each unit exhibits covariation between incompatible element ratios such as Zr/Sm and Nb/La or Gd/Yb, Sr/Nd and Ba/La, and Nb/Y and Zr/Y, which are consistent with mixing relationship between two or more mantle domains. These characteristics are unlike those of intrusions on the NW shoulder of the MCR, but resemble those of mafic rocks occurring in the East Kenya Rift. The results imply that an unusual and long-lived mantle source was present in the NE MCR for at least 34 Myr (spanning the 1140 Ma Abitibi dykes and the 1106 Ma Marathon series) and indicate potential for Cu–PGE mineralization in an area much larger than was previously recognized. [ABSTRACT FROM AUTHOR]

The Late Triassic Guichon Creek batholith is a large (~ 1800 km2), composite, zoned batholith that hosts several large porphyry Cu-Mo deposits of the Highland Valley Copper district. The batholith consists of intrusive rocks that range in composition from gabbro to quartz monzonite. Adjacent to the mafic margin of the batholith is the Gump Lake granodiorite to quartz monzonite stock. A new U-Pb zircon age of 218 ± 0.18 for the Gump Lake stock indicates that magmatism in the region began at least seven million years prior to the emplacement of the main Guichon Creek batholith rocks at 211 Ma. Zircons from fifteen samples from the Guichon Creek batholith were analyzed by laser ablation ICP-MS to characterize the magmatic evolution and ore fertility of the batholith. The trace element composition of zircon record early, lower crustal, fractional crystallization followed by five pulses of magma recharge and mixing in an upper-crustal, oxidized, magma chamber as well as degassing of the magmatic-hydrothermal fluids that formed the porphyry copper deposits. Zircons from the early barren rocks have chondrite-normalized Eu/EuN* values of 0.19 to 0.56 and estimated temperatures of 850 to 750 °C. The middle to late intrusions that host porphyry copper mineralization have zircon Eu/EuN* values of 0.30 to 0.74 and slightly lower estimated temperatures of 800 to 600 °C. Late porphyritic stocks and dikes from the mineralized centers contain zircon crystals elevated in Y, Nb, Ta, and REE concentration relative to zircon from the earlier intrusions. This distinct change in zircon composition coincides with the copper mineralization, suggesting that zircon chemistry can be used as a tool to identify the genetic evolution of a crystallizing magma chamber and potential for mineralization. [ABSTRACT FROM AUTHOR]

The Miocene Cuonadong leucogranites in the easternmost section of the Tethyan Himalaya, Southern Tibet, are characterized by two types of tourmaline. Tourmaline occurs as needle-like crystals in the two-mica ± tourmaline granites (Tur G) and large patches in the pegmatites (Tur P). Both the granite and the pegmatites yield Miocene ages (ca. 20 Ma) based on monazite U(-Th)-Pb dating, whereas 40Ar/39Ar geochronology of the coarse-grained tourmalines (Tur P) crosscut by pegmatite veins yielded an Eocene mini-plateau age of 43 ± 6 Ma. Major element concentrations of tourmaline indicate that both Tur P and Tur G belong to the schorl group with a magmatic origin, but trace elements such as V indicate that they are not cogenetic. Boron isotopes suggest that Tur P (average –9.76‰) was derived from typical crustal sources, whereas Tur G (average –7.65‰) contains relatively more mafic input. The capture of Eocene tourmaline by the Miocene leucogranites at Cuonadong suggests that the crustally derived Eocene magmatism may have occurred in the southern Tethyan Himalaya. Identification of the inherited magmatic tourmaline (Tur P), although not common, challenges the current application of tourmaline chemistry to the investigation of magmatic-hydrothermal systems. [ABSTRACT FROM AUTHOR]

The Atlas porphyry Cu–Au deposit is located in central Cebu Island in the Philippines, with a proven mineral reserve of 1420 Mt at 0.45% Cu, 0.24 g/t Au, 0.018 g/t Mo, and 1.8 g/t Ag. It is associated with the Lutopan quartz diorite porphyry stock that was emplaced into the Cretaceous volcano-sedimentary sequences of the Cansi Formation. Two stages of hypogene alteration have been identified at Atlas: stage I quartz–magnetite ± chalcopyrite ± pyrite veins associated with potassic and propylitic alteration and stage II anhydrite–pyrite–chalcopyrite ± specularite veins associated with phyllic alteration. Supergene gypsum veins are also present. Mineralization is mainly associated with the stage I and stage II veins. The Lutopan quartz diorite porphyry yielded a zircon U–Pb age of 108.5 ± 1.6 Ma and is characterized by high Sr/Y (54–69), with the corresponding magma having high oxygen fugacity (avg. ΔFMQ +2.7, avg. Ce4+/Ce3+ of zircon = 439) and H2O concentrations (presence of amphibole and biotite phenocrysts) and low magmatic temperatures (avg. Ti-in-zircon thermometry = 706 °C). The relatively low La/Yb ratios (9–11), listric-shaped normalized REE patterns with weak or absent Eu anomalies, together with zircon εHf(t) values of 3.4 to 10.0, whole-rock ISr values of 0.70373–0.70382, εNd(t) values of 2.4–3.4 and Mg numbers of 49–53 suggest that the Lutopan quartz diorite porphyry was likely derived from partial melting of young lower continental crust or interaction between asthenospheric melts and lower crust melts, that evolved to adakite-like trace element compositions through amphibole fractionation. Stage I veins yielded a pyrite Re–Os isochron age of 110.2 ± 5.6 Ma, making Atlas the only Mesozoic porphyry deposit discovered in the Philippines. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic English Bay Complex consists of a granite-rhyolite assemblage outcropping on the shores of Lake Nipigon in western Superior Province, Canada. It intrudes Neoarchean rocks and is disconformably overlain by a rift–infracratonic basin sedimentary succession recording subsidence following a heating event. The granites and rhyolites are characterized by light rare-earth element (LREE) enrichment (La/Smn = 2.8–5.1) and only weakly fractionated heavy REE (HREE; Gd/Ybn = 1.1–1.6). The felsic igneous rocks are high-K, enriched in Zr, Nb, Y, and REE satisfying all the criteria for an A-type suite. Trace element geochemistry, particularly the absence of any negative Nb anomalies, indicates this melt did not originate in a suprasubduction zone setting, unlike the St. Francois Mountain Complex to the south. The English Bay Complex may record the northern portion of a Mesoproterozoic plume track— a plume that possibly led to earlier igneous activity and infracratonic basin formation to the north and would later interact with a suprasubduction zone margin to the south. [ABSTRACT FROM AUTHOR]

Cerium (Ce) anomalies can be used to distinguish diagenetic and hydrogenetic nodules, making them an important discriminator for the genesis of marine ferromanganese nodules. To understand the enrichment and adsorption mechanisms of Ce in different types of ferromanganese nodules, we conducted mineralogical and geochemical studies on ferromanganese nodule layers formed through both hydrogenetic and early diagenetic processes as well as adsorption experiments on synthetic δ-MnO 2 to monitor the Ce uptake during the different processes. The major and trace element contents of natural ferromanganese nodule layers were investigated by SEM, EPMA and LA-ICP-MS analysis. The marine nodule studied in this study consisted of a core of fish tooth and a rim that could be divided into the hydrogenetic (type I) and early diagenetic (type II) layers based on their mineralogy and Mn/Fe ratios. The Mn oxide mineral assemblage is composed of todorokite, buserite, birnessite, and vernadite (δ-MnO 2) and occurred in both type I and II layers. The type I layer has laminated structures with a low Mn/Fe ratio (1.1–3.2; averaging at 1.7), and low Cu, Ni and Mg contents consistent with a hydrogenetic genesis. The type II layer has a columnar and stromatolitic structure with a high Mn/Fe ratio (5.1–54.0; averaging at 23.3) and high Cu, Ni and Mg contents that are similar to early diagenetic nodules. The ΣREE contents in type I and type II layers are 1405–3506 ppm (averaging at 2091 ppm) and 199–1232 ppm (averaging at 674 ppm), respectively, indicating that the REE is enriched in the hydrogenetic type I layers. Strong positive Ce anomalies are present type I layers ranging from 1.2 to 2.5 (averaging 1.9), but only slightly positive are seen in type II ranging from 0.4 to 2.4 (averaging at 1.0). Synthetic experiments to monitor the Ce uptake process show that Ce can be adsorbed onto δ-MnO 2 with the XRD and FTIR patterns suggesting that the structure of δ-MnO 2 did not change significantly, consistent with Ce behavior in hydrogenetic nodules. The results suggest that Ce is predominantly concentrated in hydrogenetic nodules in an oxic environment, whereas in the early diagenetic layer, there is less oxidation and fixation of Ce due to the suboxic conditions. Our findings are consistent with Ce anomalies in marine Fe-Mn nodules being the result of Mn oxide oxidation adsorption and then fixation (oxidation) after adsorption. [Display omitted] • Morphology and geochemistry results confirm the hydrogenetic and diagenetic genesis of the ferromanganese nodule. • LA-ICP-MS analysis shows that Ce anomalies are distinctly different in hydrogenetic and diagenetic nodules. • Adsorption experiments suggest that Ce is adsorbed on the surface of δ-MnO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrite-bearing veins at Qulong can be divided into seven subclasses. • The contents of Co and Ni and the ratios of Co/Ni and Ni/Se in pyrite can be used to investigate the evolution of fluid composition, temperature and oxygen fugacity. • Changes in trace elements and S isotopes in pyrite can be used to investigate the evolution of magmatic-hydrothermal fluids. The post-collisional Qulong porphyry Cu-Mo deposit is the largest in the Gangdese Cu belt, southern Tibet. Despite many previous studies, the evolution of ore-forming fluids in the Qulong deposit remains controversial. Pyrite-bearing veins at Qulong can be divided into seven subclasses, including Mt-type, Bt-type, A-type, B-type, C-type, D-type, and E-type veins. To decipher the evolution of magmatic-hydrothermal fluids at Qulong, in situ LA-ICP-MS trace element and sulfur isotope compositions of pyrites from different veins were analyzed. The δ34S values (+1.01‰ to + 4.28‰) for pyrites indicate a magmatic sulfur source and the high Se/S ratios of pyrite at Qulong are consistent with hydrothermal fluids being mainly magma-derived. The low Co/Ni ratio (0.01–0.1) of pyrite in Mt-type vein suggests that the earliest magmatic-hydrothermal fluids may have contributed from mafic magma injection. From Mt- to Bt- to A-type veins, the δ34S values in the hydrothermal fluids decrease as the temperature decreases, whereas the Cu and Co contents increase and the As and Ni contents decrease. In B- and C-type veins, the relatively high and stable Co and Ni contents and the range of δ34S isotope values in pyrite indicate the existence of multiple-stages of magmatic-hydrothermal fluids during the main mineralization period. During the late stages of mineralization, the decrease of Co, Ni and As contents and increase of Cu in pyrite in D- and E-type veins, as well as the narrow range of δ34S values, may be due to decreasing temperature as a result of fluid dilution caused by mixing with meteoric waters. The slightly negative δ34S fluid values for chalcopyrite (-1.56‰ to −0.75‰) in sample Q711-1968 also suggests the addition of external water at Qulong. [ABSTRACT FROM AUTHOR]

[Display omitted] • LA-ICP-TOFMS was used for rapid and high-resolution element maps of Fe-Mn nodules. • 10 * 9 mm2 and 700 * 350 µm2 size area took 2.27 h and 0.62 h, respectively. • Macro area element maps indicate that the nodule underwent mineral maturation. • LA-ICP-TOFMS element mapping is suitable for soft, porous samples. Polymetallic nodules are one of the most ubiquitous critical metal reservoirs in the deep sea during early diagenesis. Trace elements including REY (Rare earth elements + Y), can provide a wealth of information to document the source-to-sink (STS) processes and critical metals enrichment regimes. Element imaging is an important "see-through" technique to display the distribution of multi-elements to understand the respective concentration relationship. However, traditional elemental mapping of macro (several millimeters) and micro (tens of micrometers) areas has remained a major challenge due to the long analytical time and low lateral resolution. Here, we apply inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS), coupled to laser ablation (LA) with a low-dispersion two-volume sample cell and a dual concentric injector at both the macro- and micro-scales. LA-ICP-TOFMS mapping was applied to an entire polymetallic nodule (size of 10 * 9 mm2 @ 40 µm2 spot size, 1300 µm/s scan speed and 15 Hz frequency) and microdomains with microlayers (size of 700 * 350 µm2 @ 1 µm2, 200 µm/s and 200 Hz), respectively. The intra-nodule distribution patterns of elements are mainly controlled by the occurrence minerals. For example, the distribution patterns of some metals (e.g., Cu, Co, Ni) are similar to that of Mn, indicating these metals host in Mn-phase minerals. There is a trend of decreasing and then increasing of these elements from the inner to the outer layer, suggesting that the redox environment may have undergone a process from oxic to suboxic and then to oxic during the growth process. Our results demonstrate the feasibility of LA-ICP-TOFMS analysis on soft and porous materials, whose advantages include a shorter time and higher lateral resolution compared with traditional LA-ICP-QMS, expanding the geochemical mapping techniques for deep-sea early diagenetic sediments samples. [ABSTRACT FROM AUTHOR]

Protracted magma storage in the deep crust is a key stage in the formation of evolved, hydrous arc magmas that can result in explosive volcanism and the formation of economically valuable magmatic-hydrothermal ore deposits. High magmatic water content in the deep crust results in extensive amphibole ± garnet fractionation and the suppression of plagioclase crystallization as recorded by elevated Sr/Y ratios and high Eu (high Eu/Eu*) in the melt. Here, we use a novel approach to track the petrogenesis of arc magmas using apatite trace element chemistry in volcanic formations from the Cenozoic arc of central Chile. These rocks formed in a magmatic cycle that culminated in high-Sr/Y magmatism and porphyry ore deposit formation in the Miocene. We use Sr/Y, Eu/Eu*, and Mg in apatite to track discrete stages of arc magma evolution. We apply fractional crystallization modeling to show that early-crystallizing apatite can inherit a high-Sr/Y and high-Eu/Eu* melt chemistry signature that is predetermined by amphibole-dominated fractional crystallization in the lower crust. Our modeling shows that crystallization of the in situ host-rock mineral assemblage in the shallow crust causes competition for trace elements in the melt that leads to apatite compositions diverging from bulk-magma chemistry. Understanding this decoupling behavior is important for the use of apatite as an indicator of metallogenic fertility in arcs and for interpretation of provenance in detrital studies. [ABSTRACT FROM AUTHOR]

Abstract The Jiaobei Terrane in the southeastern North China Craton (NCC) witnessed intense magmatic pulses during Mesozoic in response to lithospheric thinning. These include sporadic felsic-porphyritic dikes which preserve important information on the magmatic processes and of its implications on lithospheric thinning. Here we present a detailed investigation of representative felsic-porphyritic dikes based on whole-rock geochemical analysis, zircon LA-ICPMS U-Pb geochronology, trace elements and hafnium isotopic compositions. Our results identify stages of felsic dikes in the Jiaobei Terrane with ages in the range of 131–127 Ma and 123–116 Ma. The early stage felsic dikes (ESFDs) have negative zircon ɛ Hf (t) (−22.4 to −11.1), high zircon Eu N /Eu N * (0.41–0.92) and Ce4+/Ce3+ (62–944), low Ti-in-zircon crystallization temperatures (524–738 °C), and are geochemically comparable to the coexisting Guojialing granodiorite. Abundant inherited zircons and scattered zircon Hf, Yb/Gd, Th/U, and Ce/Sm values suggest that the magmas from which the dikes formed involved crustal contamination. They are interpreted to be the hypabyssal phase of the Guojialing suite sourced from the Paleoproterozoic lower crust of the eastern NCC with input of mantle components, associated with extensive crust-mantle interaction during the peak lithospheric thinning. The late stage felsic dikes (LSFDs) are characterized by variable zircon ɛ Hf (t), Eu N /Eu N * and Ce4+/Ce3+ values (−20.1 to −12.2, 0.38–0.88 and 64–956 for the granodiorite- and quartz-porphyritic dikes; −27.6 to −16.2, 0.17–0.75 and 22–503 for the monzogranite-porphyritic dikes), low Ti-in-zircon crystallization temperatures (562 to 774 °C), and display geochemical similarity with the Aishan granitoids. Systematic variations of zircon Hf, Yb/Gd, Th/U and Ce/Sm suggest that fractional crystallization of hornblende played a significant role in the formation of the late dikes. The LSFDs originated from the Neoarchean-Paleoproterozoic lower crust of the NCC with heterogeneous involvement of lesser amounts of mantle materials than the early dikes, consistent with weak crust-mantle interaction during the waning stage of lithospheric thinning. In the LSFDs, the granodiorite and monzogranite porphyries are broadly coeval (123–118 Ma) with large scale gold mineralization in the area as also favored by the high zircon Ce4+/Ce3+ ratios. Our study also provides new insights into the formation of gold deposits. Graphical abstract Unlabelled Image Highlights • Two distinct pulses of Cretaceous felsic dike emplacement in the Jiaobei Terrane • Early stage emplaced at 131-127 Ma with magma sourced from Paleoproterozoic lower crust • Late stage formed at 123-116 Ma with magma source from Neoarchean-Paleoproterozoic crust • High zircon Ce4+/Ce3+ and EuN/Eu N * ratios reflect oxidized conditions with potential to generate metallic mineralization. [ABSTRACT FROM AUTHOR]

The Machangqing Cu-Mo-dominated polymetallic deposit is a porphyry-skarn-epithermal Cu-Mo (-Au) metallogenic system located in the middle part of the Jinshajiang–Ailaoshan alkaline porphyry metallogenic belt. The skarn mineralization of the Machangqing deposit mainly occurs along the contacts between the alkalic porphyry intrusions and the surrounding Lower Ordovician Xiangyang Formation rocks. We present LA-ICP-MS U-Pb ages and trace element data for titanite from the Machangqing deposit in order to investigate the origin of this deposit. Based on mineral textures and assemblages, two types of titanite are recognized in Machangqing: magmatic titanite (Type I) from the granite porphyry and hydrothermal titanite from the mineralized skarn. The coarse-grained magmatic titanite is euhedral and occurs as discrete grains in the interstices of feldspar, quartz and biotite, whereas fine- to medium-grained hydrothermal titanite crystals (Type II) are euhedral to subhedral and occur in association with skarn minerals such as garnet, pyroxene and magnetite. Magmatic titanite has lower FeO, Al 2 O 3 , F and Nb/Ta but higher TiO 2 , Th/U, HFSEs and Lu/Hf than hydrothermal titanite. The magmatic titanite has higher LREE/HREE ratios and total REE contents with stronger negative Eu anomalies than its mineralized skarn counterpart. Trace elemental characteristics of hydrothermal titanite in Machangqing are consistent with relatively low F contents and oxygen fugacities when compared to the neighboring Beiya gold-dominated polymetallic deposit in the same metallogenic belt. The weighted average 206 Pb/ 238 U age of 34.3 ± 1.2 Ma of hydrothermal titanite is within error but slightly younger than the age of magmatic titanite (37.5 ± 4.1 Ma), indicating that the skarn mineralization followed the emplacement of the granite porphyry and was broadly coeval with the porphyry mineralization. The porphyry and skarn types of mineralization at Machangqing were formed from the same metallogenic system. Different ore-forming conditions, such as oxygen fugacities and F contents, might be responsible for different metal enrichments at the Machangqing and Beiya deposits. [ABSTRACT FROM AUTHOR]

Skarn alteration occurs over a wide range of temperatures and geological settings, and hydrothermal magnetite (a common mineral in skarn) represents a potentially useful temperature and tectonic indicator. Here we describe a new 2D/3D quantitative element mapping approach to evaluate the element mobility of magnetite during skarn alteration/mineralization. Magnetite grains from the giant Beiya Fe-Au skarn deposit (Yunnan, SW China) are either coarse-grained euhedral (hexagonal) with core-rim zoning (type I) or subhedral unzoned (type II) coexisting with (some enclosing) garnet. Concentrations of Na, Mg, Al, Si, Ca, Sr, Cr and Mn in the type I magnetite core and rims are drastically different, which are high in the core and outer rim and low in the inner rim. This suggests fluid geochemical fluctuations, probably led by multiple phases of ore fluid incursions that are common in many world-class skarn deposits. Concentrations of Mg, Al, Si, Ca, Mn and Sr in the garnet are higher than those in type II magnetite. This is likely because the earlier garnet crystallization (during the prograde skarn alteration) had depleted these elements in the later magnetite ore fluids. Both the garnet and the magnetite core are characterized by high Ti concentration. The high Ti concentration in the garnet is governed by the crystal structure, while that of Ti in hydrothermal magnetite is governed by Ti mobility. The 3D-mapping and simulation modeling have shown clear element variation patterns in some magnetite grains that were previously determined to be compositionally homogeneous by spot analysis. Our new 2D/3D-mapping have revealed the presence of mineral inclusions such as garnet and calcite as constrained by the trace element mobility during the replacement of garnet by magnetite, as shown in the euhedral zoned magnetite in garnet pseudomorph. [ABSTRACT FROM AUTHOR]