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Tourmaline is widespread at the Bilihe porphyry gold deposit in Inner Mongolia, China. Five types of tourmaline are recognized based on their occurring locations and microscopic structures: (1) Tur-A in quartz–magnetite ± K-feldspar veins and related potassic-altered rocks, (2) Tur-B in auriferous quartz veinlets, (3) Tur-C in the intermediate argillic shell, (4) Tur-D in late quartz–carbonate–tourmaline–pyrite veins, and (5) Tur-HB in hydrothermal breccia pipes, consisting of three sub-generations (Tur-HB1, -HB2, and -HB3). Almost all these tourmalines have a schorlitic–dravitic composition and belong to the alkali group. Most of the tourmalines contain high Al contents, which may suggest that the fluids are Al-enriched, and that (□Al)(NaFe)-1 and (AlO)(R2+)-1(OH)-1 exchanges have dominated their elemental substitutions. Tur-A and -B yield similar REE patterns with no strong fractionation of LREE and HREE, whereas LREE-enrichment and HREE-depletion characterize Tur-C and Tur-D; Tur-HB1 and -HB2 have flat REE patterns. Tourmalines in hydrothermal veins always show negative Eu anomalies, whereas the ones replacing plagioclase in the altered rocks yield positive Eu anomalies. The mineral precipitation and assimilation of host rocks probably both contributed to the variable compositions of Bilihe tourmaline. Tur-A−D from the main orebody all yield positive δ11B values ranging from +0.7 to +6.3‰, whereas Tur-HB1−HB3 from the hydrothermal breccia pipe show negative δ11B values of −8.8 to −3.5‰. Magmatic hydrothermal fluids enriched in isotopically light boron could have dominated the formation of Tur-HB. In contrast, the heavy boron in Tur-A−D was probably leached from the widespread marine carbonates around the deposit. Systematic contrasts in the trace element compositions of tourmaline from different mineralization types and granitic rocks suggest that (Sn + Li) vs. (Ni + V + Zn), (∑REE + Y + Zr) vs. (Ni + V + Zn) and V vs. Zn are potential elemental groups for distinguishing tourmaline from different environments.

The Qiyugou Au deposit, located in the Xiong'ershan ore cluster of central China, consists of breccia pipe hosted Au ore bodies (>60 t Au) and newly discovered porphyry ore body (8 t Au). The porphyry Au mineralization occurs in the silicified core of the apical part of porphyritic granite stock which shows close spatial relationship with the auriferous breccia pipes. Here we present an integrated study involving detailed field investigation, textural studies, in situ pyrite trace element and sulfur isotope analysis, and U-Pb and Re-Os geochronology to elucidate the genetic relationship and hydrothermal evolution of the porphyry and breccia pipe mineralization. The SIMS sulfur isotopic analyses for the five pyrite generations show consistent δ34S values between −3.6‰ and 0.6‰, indicating that the two styles of Au mineralization had a mixed source including crustal and mantle-derived components. Zircon LA-ICP-MS U-Pb geochronology of two porphyritic granites yield weighted mean ages of 133.0 ± 0.6 Ma and 130.3 ± 0.9 Ma, and six molybdenite samples display an isochron age of 131.3 ± 1.1 Ma, representing the timing of granitic magmatism and Au mineralization in the 189 porphyry ore body. Available geochronological data allow us to constrain the timing of granitic magmatism and gold mineralization to be 135.6–134.1 Ma in the breccia pipes and 133.0–128.6 Ma in the porphyry ore. Among the five pyrite generations, Py1b and Py2b from the J4 breccia pipe are characterized by higher Co, Ni, and comparable contents of other elements (e.g. Au, Ag, Te, Pb, Zn, Cu and Bi) than those in Py1p, Py2p and Py3p from the porphyry ore. The widely consistent metal concentrations and linear relationship of metals in pyrite between the breccia pipe and porphyry ore are most probably the result of fluid exsolution from the same magmatic-hydrothermal system, whereas the enriched Co and Ni values from the J4 breccia pipe can reflect the composition of pyrite precipitating fluid at the early stage of the prolonged magmatic-hydrothermal system. The Qiyugou porphyry and breccia pipe mineralization show close spatial-temporal association and consistent source materials, and thus we propose that they resulted from multiple pulses of fluid exsolution from a large, deep-seated magma chamber.

A breccia pipe is a cylindrical- or irregular-shaped mass of brecciated rock. A breccia consists of broken, angular fragments of rock cemented together by a fine-grained matrix. Hydrothermal breccia pipes form when hydrothermal solutions force their way towards the surface through zones of weakness or fracture zones and naturally break up the rocks in the process, i.e., hydrofracturing; breccia pipes can also form by collapse. Hydrothermal breccia pipes can contain ore deposits and, as will be discussed later, are associated with some large oil and gas accumulations in southeastern Utah.

For over 70 years, closed topographic depressions developed in siliciclastic rocks of the Cumberland Plateau have been hypothesized to form via collapse of rock into caverns formed in the carbonate-rich rocks below. We made observations of surface characteristics and applied geophysical methods across two of these depressions on the western part of the plateau to collect subsurface information and test the cave collapse hypothesis. Electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) were conducted at both Sites 1 and 2 and two-dimensional (2D) multi-channel analysis of surface waves (MASW) was conducted at Site 2. Three zones of material are interpreted at both sites based on field observations, and variations in density (velocity) and resistivity characteristics; a relatively thin cover of organic matter and colluvium, sandstone bedrock primarily observed at the rims and upper slopes of the depression, and a possible boulder/rubble zone identified towards the centers of the depressions. Details derived from LiDAR data, field observations and collected geophysical data for Site 2 allow for the projection of a circular breccia pipe in the subsurface. A 3-stage model of development is proposed for these features: A Youthful Stage occurs after initial collapse of surface material into a subsurface cavity in which the depression has a cylindrical form. In the Mature Stage, the slopes have shallowed, and slope adjustments are made as the breccia pipe fills and settles. Bedrock cliffs are mechanically weathered and influenced by gravity, forming talus that covers slopes and the floor with colluvium mixed with organic matter. The Degraded Stage is entered when the breccia pipe has settled, the bedrock exposures are covered, and the depression begins to fill. The depressions studied for this research are classified as being in the Mature stage. Future geophysical surveys and additional geologic mapping and field work at these and other depressions on the plateau will add to our understanding of their development and evolution over time.

China’s W–Sn resources are dominant on a global scale. A series of Sn–polymetallic deposits has been found in recent years at depth on the flanks of known volcanic–subvolcanic Cu–Pb–Zn–Ag deposits in the Southern Great Xing’an Range, NE China. The large-scale Weilasituo tin–polymetallic deposit, formed at the depth of the Weilasituo Cu–Zn deposit, is most typical of these types of deposit. Tin–polymetallic orebodies are hosted in the early Paleozoic Xilingol Complex, and their mineralization is closely related to Early Cretaceous quartz porphyry. In this contribution, bulk-rock and mica chemical compositions, Re–Os geochronology, and He–Ar isotopic analyses are described in addressing the ore-formation mechanism of the deposit. Geochemical characteristics indicate that the ore-bearing quartz porphyry corresponds to the I-type granite serie. Five types of mica have been identified in the study area based on detailed petrography and EPMA and LA–ICP–MS analyses: (i) early magmatic Fe–Li mica in albitized quartz porphyry; (ii) late magmatic Fe–Li mica in mineralized quartz porphyry; (iii) hydrothermal Fe–Li mica in a cryptoexplosive breccia pipe (distributed around breccia fragments); (iv) Fe–Li mica in quartz veins; and (v) Fe–Li mica in plagioclase gneiss (wall rock). Magmatic zinnwaldite from the upper mineralized part of the quartz porphyry is enriched in Nb (100–160 ppm) and Ta (100–150 ppm). Hydrothermal zinnwaldite from the explosive breccia, quartz veins, and surrounding gneiss is unusually rich in Mg (up to 3.4 wt% MgO) and Sn (up to 200 ppm). 3He/4He ratios of the Weilasituo tin–polymetallic and Cu–Zn deposits are in the ranges 3.38–4.91 Ra and 4.8–4.9 Ra, respectively, indicating ore-forming fluids sourced from mixed crustal and mantle materials. Molybdenite Re–Os dating of W mineralization yielded an isochron age of 129.0 ± 4.6 Ma, similar to the porphyry crystallization and mineralization ages of the Weilasituo tin–polymetallic deposit, and also consistent with the mineralization age of the Cu–Zn deposit. We propose a new metallogenic model, with all subtypes of W–Sn–Cu–Pb–Zn–Ag mineralization in the Weilasituo area belonging to a single complex metallogenic system. Compared with other ore districts, ore-related granitoids in the Southern Great Xing’an Range display relatively uniform emplacement ages and were derived from partial melting of juvenile lower crust rather than old basement. Their ore-forming fluid source was greater influenced by mantle fluids than which found in South China.

The biotic exposure and uptake of radionuclides and potential health effects due to breccia pipe uranium mining in the Grand Canyon watershed are largely unknown. This paper describes the use of the RESRAD-BIOTA dose model to assess exposure of small rodents (n = 11) sampled at three uranium mine sites in different stages of ore production (active and postproduction). Rodent tissue and soil concentrations of naturally occurring uranium (U, U, and U), thorium (Th, Th, and Th), and radium (Ra) radioisotopes were used in the dose model. The dose assessment results indicated that the potential internal, external, and total doses to rodents were below the US Department of Energy's biota dose standard of 1 mGy d. As expected, tissue concentrations of U, U, and Th were in approximate equilibrium; however, Ra results in tissue were 1.25 to 5.75 times greater than U, U, and Th tissue results for 10 out of 11 samples. Soil at the three sites also displayed Ra enrichment, so it is likely that the Ra enrichment in the rodents was from soil via typical activities (i.e., burrowing, incidental ingestion, bathing, etc.) or by dietary uptake of translocated Ra. The results suggest that Ra is more mobile in this environment and bioaccumulates in these rodent species (e.g., in bones via the bloodstream). Internal dose accounting suggests that Ra is the radionuclide of most concern for rodent exposure and health.

The Qiyugou district is one of the most important gold deposit distribution areas in the Xiong’ershan region, North China Craton. These deposits are hosted in Archean Taihua Supergroup rocks as gold-bearing breccia pipes. Here, we report a detailed in situ analysis of trace elements and S-Pb isotopes in sulfides from different ore stages, in combination with electron probe microanalysis of ore minerals from the gold-bearing J4 breccia pipe in the Qiyugou district, to unravel the gold distribution and their textural relationships to pyrite, the metal sources and S-Pb isotopic composition variations during the ore-forming processes. The Qiyugou breccia pipes hosted gold ore (over 70 t Au, average grade of 2–5 g/t) that formed in four mineralization stages, i.e., an early K-feldspar-biotite-magnetite-quartz-pyrite (Py-1) stage (I) that can be further divided into two substages, namely the Ia K-feldspar-biotite-magnetite stage and the Ib quartz-pyrite stage; a gold-pyrite (Py-2)-quartz stage (II); a gold-quartz-polymetallic sulfide (Py-3) stage (III); and a late quartz-carbonate stage (IV). The visible native gold and electrum grains occur as small inclusions and disseminations in the fractures within Py-2 and Py-3. Tellurides and Bi-Pb-minerals are widespread in the stage II stockworks and veins, as is intergrowth with visible native gold and Py-2. In situ LA-ICP-MS trace element analysis reveals the presence of invisible gold hosted in three types of pyrite with extremely low Au content (Py-1 ≤ 0.05 ppm; Py-2 ≤ 0.03 ppm; Py-3 ≤ 0.02 ppm). Concentrations of Te, Bi, and Pb in pyrite are high and correlate well with Au concentrations, but As content is low. Therefore, the Te, Bi and Pb played a significant role in gold mineralization in As-deficient ore fluids in the J4 gold-bearing breccia pipe from the Qiyugou district. High-precision in situ laser ablation multiple collector inductively coupled mass spectrometry (LA-MC-ICP-MS) lead isotope analyses indicate that the sulfides have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios from 17.250 to 17.629, from 15.401 to 15.621, and from 37.649 to 38.290, respectively, which are similar to the granite porphyry in the district and indicative of their similar lead sources. High-precision in situ LA-MC-ICP-MS sulfur isotope analyses of pyrite show a large δ34S variation (e.g., from −18.1 to −11.1 per mil for Py-1, from −12.2 to − 6.6 per mil for Py-2, and from −4.9 to −1.6 per mil for Py-3) with a remarkable increasing trend from stage I, stage IIto stage III. This trend may record a decreasing oxygen fugacity of the ore-forming fluids during mineralization.

The Puy-les-Vignes W deposit, located in the northwestern French Massif Central (FMC), is a rare occurrence of a wolframite-mineralized hydrothermal breccia pipe hosted in high-grade metamorphic gneisses. We present an integrated study of this deposit aiming to characterize the ore-forming hydrothermal system in link with the Variscan late-orogenic evolution of the FMC. Based on a set of representative samples from the host rocks and mineralization, we describe a detailed paragenetic sequence and we provide the major and trace element geochemistry of the granitic rocks and W–Nb–Ta–Sn–Ti oxide minerals, in situ U/Pb and 40Ar/39Ar geochronology, and a fluid inclusion study of quartz and wolframite. We demonstrate that the formation of this W-mineralized breccia pipe results from a multistage development related to four major episodes during the late Carboniferous. The first episode corresponds to the emplacement of an unexposed peraluminous granite at ca. 324 Ma, which generated microgranite dykes exposed at the present-day surface. The second episode is the formation of the quartz-supported breccia pipe and wolframite mineralization at ca. 318 Ma at a paleodepth of 7 km. The mineralizing fluids have a H2O–NaCl–CO2–CH4–N2 composition, a moderate-salinity ( 400 °C) during lithostatic to hydrostatic pressure variations caused by hydrofracturing of the host rocks. Wolframite deposition is interpreted to result from a W-rich intermediate-density magmatic fluid that exsolved from an evolved leucogranite and interacted with volatile-rich metasedimentary country rocks and/or possibly mixed with low-salinity metamorphic fluids of deep origin. The third episode corresponds to magmatic-hydrothermal Nb–Ta mineralization overprinting the W-mineralized system interpreted to be related to the intrusion at ca. 311 Ma of a rare-metal granite, which is part of a regional peraluminous rare-metal magmatism during the 315–310 Ma period. Finally, the last episode corresponds to disseminated Bi ± Au–Ag mineralization emplaced at ca. 300 Ma, which shares similar mineralogical features with late Carboniferous orogenic gold deposits in the FMC. The Puy-les-Vignes W deposit records, therefore, a multistage and long-lived development that extends over a timespan of 25 million years in a regional setting dominated by protracted peraluminous magmatism and high-temperature and low-pressure metamorphism. Although the local environment of ore deposition is atypical, our results show that the mineral assemblages, alteration styles, and fluid characteristics of the Puy-les-Vignes breccia pipe are similar to those of other peri-granitic W deposits in the FMC.

Assessing chemical loading from streams in remote, difficult-to-access watersheds is challenging. The Grand Canyon area in northern Arizona, an international tourist destination and sacred place for many Native Americans, is characterized by broad plateaus divided by canyons as much as two-thousand meters deep and hosts some of the highest-grade uranium deposits in the U.S. From 2015-2018 major surface waters in Grand Canyon were monitored for select elements associated with breccia-pipe uranium deposits in the area, including uranium, arsenic, cadmium, and lead. Dissolved constituents in the Colorado River were monitored upstream (Lees Ferry), in the middle (Phantom Ranch), and downstream (Diamond Creek) of uranium mining areas. Concentrations of uranium, arsenic, cadmium, and lead at these main-stem sites varied little during the study period and were all well below human health and aquatic life benchmark criteria (30, 10, 5, and 15 μg/L maximum contaminant levels and 15, 150, 0.8, and 3.1 μg/L aquatic life criteria, respectively). Additionally, dissolved and sediment-bound constituents were monitored during a wide range of streamflow conditions at Little Colorado River, Kanab Creek, and Havasu Creek tributaries, whose watersheds have experienced different levels of uranium mining activities over time. Samples from the tributary sites contained ≤3.8 μg/L of dissolved cadmium and lead, and ≤17 μg/L of dissolved uranium. Dissolved arsenic also was mostly below human and aquatic life criteria at Little Colorado River and Kanab Creek; however, 63% of water samples from Havasu Creek were above the maximum contaminant level for arsenic. Arsenic in suspended sediment was greater than sediment quality guidelines in 9%, 35%, and 35% of samples from Little Colorado River, Kanab Creek, and Havasu Creek, respectively. At the concentrations observed during this study, tributaries contributed on average only about 0.12 μg/L of arsenic and 0.03 μg/L of uranium to the main-stem river. This study demonstrates how chemical loading from mined watersheds may be reliably assessed across a wide range of flow conditions in challenging locations.

The Cretaceous Koegel Fontein igneous complex is situated on the west coast of South Africa, and has a high proportion of rocks with abnormally low δ18O values. The rocks with the lowest δ18O values (− 5.2‰) belong to intrusive matrix-supported breccia pipes and dykes, containing a variety of clast types. The breccia rocks range in SiO2 from 44 to 68 wt% and their whole-rock δ18O values vary between − 5.2‰ and + 1.8‰. The major and trace element composition of the breccia rocks is consistent with them containing variable proportions of clasts of Cretaceous intrusive rocks and basement gneiss and the matrix being fluidized material derived from the same source as the clasts. Based on the nature of the clasts contained in the breccia, it was emplaced just prior to intrusion of the main Rietpoort Granite at 134 Ma. All components of the breccia have low δ18O value and, at least in the case of the gneiss clasts, this predates incorporation in the fluidized material. Although the early Cretaceous appears to have been a period of cold climate, it is unlikely that the δ18O values of ambient precipitation (~− 10‰) would have been low enough to have generated the required 18O-depletion. The basement gneiss was probably ~ 2–3 km below the Cretaceous surface, minimizing the possibility of interaction with isotopically unmodified meteoric water, and there is no evidence for foundered blocks of cover rocks in the breccia. There is, therefore, no evidence for downwards movement of material. We favour a model where basement gneiss interacted with extremely 18O-depleted fluid during crustal reworking at ~ 547 Ma, a time of global glaciation. Low-δ18O metamorphic fluids produced by dehydration melting of 18O-depleted gneiss became trapped and, as the fluid pressure increased, failure of the seal resulted in explosive upwards movement of fluidized breccia. Migration was along pre-existing dykes, incorporating fragments of these dykes, as well as the country rock gneiss.

The laminated limestones of the Crato Formation, Araripe Basin (NE of Brazil) have been investigated, as they are analogous to facies of the carbonate reservoirs of the pre-salt sequence of the Brazilian marginal basins. The Early Cretaceous Crato laminites comprise a complex range of structures that may play an important role in the porosity and permeability distribution in carbonate reservoirs. This work aims to (1) understand the control of a boundary fault zone (the Triunfo Fault, Lower Cretaceous) on the development in carbonate breccia pipes of the Crato Formation, and (2) constrain the timing of brittle deformation, based on field observations, microstructural investigation and U–Pb carbonate geochronology. The breccia pipes are observed surrounding both normal and strike-slip faults. The brittle deformation superimposed on the pipes is characterized by brecciation and veining that show multiples phases of mineralization. Our results propose the circulation of fluid along the pre-existing faults and pipes, these fluids are responsible for polyphasic deformation in the pipes. We report two U–Pb ages from carbonate-vein mineralization of 94.9 ± 3.8 Ma (Cenomanian to Turonian) and 80.2 ± 3.0 Ma (2σ) (Campanian), which provide time constraints on the brittle reactivations of the Triunfo Fault Zone, during the post-rift phase of the Araripe Basin.

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 145.8 Ma, 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 ± 1.7 Ma, 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 87 Sr/ 86 Sr 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.

The Cerro la Mina Au (Cu-Mo) porphyry-high sulfidation prospect is located in Chiapas State, southeastern Mexico, outside of the major metallogenic provinces of Mexico. The prospect is hosted by Pleistocene alkaline volcanic rocks of the Chiapanecan volcanic arc that formed in a complex triple-junction tectonic setting. Cerro la Mina's stratigraphy comprises pyroclastic flows that were intruded by monzodiorites and diorites at 1.04 ± 0.04 Ma (U-Pb, zircon), and that were overlain by debris flows and synvolcanic trachyandesite domes. The volcanic stratigraphy of Cerro la Mina is dominated by pyroclastic flows and rare basalts that are cut by the Cerro la Mina breccia pipe, a matrix-rich granular, vertically oriented, downward-tapering, polymict lithic rock unit that is host to all of the significant alteration and mineralization. A NW-trending sinistral wrench fault, which was active throughout the history of Cerro la Mina, is responsible for dismembering the prospect after mineralization. The magmatic hydrothermal system was composed of early porphyry-style potassic veins (quartz + K-feldspar ± biotite) and stage 1 pyrite that are preserved in clasts within the breccia pipe, suggesting that brecciation disrupted an embryonic porphyry system. Late potassic alteration occurred after the formation of the breccia pipe, as its matrix is strongly K-feldspar altered. Hydrothermal fluids then produced phyllic alteration composed of quartz, muscovite, illite, illite-smectite, and chlorite that is associated with stage 2 pyrite ± chalcopyrite ± molybdenite ± quartz veins. An unusual zoned pattern of advanced argillic-argillic alteration overprinted potassic and phyllic alteration. This zoning included a low-temperature ( 120°C) quartz + dickite ± kaolinite ± pyrophyllite ± alunite that occurs from 250 m to the present-day surface. The advanced argillic-argillic altered rocks host the most significant Au-Cu mineralization, which is associated with stage 3 marcasite, sphalerite, galena, and barite, and stage 4 arsenian pyrite ± enargite ± covellite. The magmatic hydrothermal system at Cerro la Mina began sometime between monzodiorite emplacement (1.04 ± 0.04 Ma; zircon U-Pb) and the precipitation of porphyry stage 2 molybdenite at 780 ± 10 ka (Re-Os). 40Ar/39Ar dating of biotite (689 ± 13 ka) records the age at which the hydrothermal system cooled below the biotite closure temperature of ~300°C and provides a maximum estimate for the onset of advanced argillic-argillic alteration. Sulfur isotope results of sulfides (–2.5 to +4.9‰; mean +0.7‰; n = 20) and a sulfate (barite; +10.5‰; n = 1) suggest a magmatic source of sulfur for all four stages of mineralization. The lack of residual quartz, rare alunite, and anomalous halloysite-kaolinite alteration may be explained by the high acid-buffering capacity of alkaline volcanic host rocks, high CO2 contents of the alkaline magma, and/or potentially by a highly reduced magmatic hydrothermal fluid. At the regional metallogenic scale, the Cerro la Mina prospect along with the nearby Santa Fe mine and Campamento deposit represent parts of a porphyry copper system—specifically, a porphyry/high-sulfidation, proximal skarn and intermediate sulfidation deposit, respectively. The characteristics of Cerro la Mina (i.e., anomalous halloysite-kaolinite alteration) broaden the window for additional discoveries to be made in the porphyry-epithermal environment.

The Middle Devonian hypogene evaporite dissolution, karst collapse resulted in the fragmentation of the Upper Devonian strata into a mosaic of differentially subsided fault blocks underlying the northern area of the Athabasca Oil Sands Deposit. Regional salt dissolution collapse developed structural troughs up to 50 km long on the sub-Cretaceous unconformity. The structural depressions formed above collapsed collinearly aligned, brine-filled, evaporite dissolution chimneys extending up to 100 m high within the Prairie Evaporite salt beds. Individual and coalesced arrays of dissolution chimneys developed along fault lineament dissolution trends that dissected the 10 km wide Prairie Evaporite salt scarp. 3D seismic images of chimney collapse structures in the Middle Devonian evaporite basin depocenter across central Saskatchewan are analogues used to interpret collapse structures evident in the Upper Devonian succession and the overlying Lower Cretaceous McMurray Formation. The Devonian-Cretaceous fault bound blocks located above the dissolution chimneys were gravity driven collapse structures. These structures included oblique rotational trajectories during the descents towards and into underlying dissolution voids. Breccia pipes were impinged along the deeper reaches of the inter-block fault planes as adjacent blocks obliquely rotated apart and towards each other, resulting in zones with compressional and extensional bed deformations during the variable but often rapid rates of vertical descent. The breccia pipes pass upward, along fault planes, into oblique shear zones with twisted beds and zigzag suture welding between adjacent blocks. Upper reaches of the collision zone, between adjacent blocks, were dominated by compressional deformations that resulted in sinkhole development bound on one side by the fault plane. Continued bed compression deformed and fragmented many sinkhole structures. Some of these collapse-induced fault block collisions suggest cataclysmic events, and caused seismicity triggered fluidization in the upper intervals of breccia pipes with mobilization as debris flows that spread across adjacent fault block surfaces.

The recently discovered Weilasituo Sn-polymetal deposit is located in the southern part of the Great Xing'an Range of Inner Mongolia, NE China, which is belonged to the eastern part of the Central Asian Orogenic Belt (CAOB). Sn-polymetal mineralization is closely related to the emplacement of the Early Cretaceous fine- to medium-grained quartz porphyry. Three types of mineralization have been recognized at Weilasituo with the disseminated and stockwork Sn-polymetal mineralization mainly hosted by the quartz porphyry, the vein-type Sn-polymetal mineralization hosted by NE-trending and WE-trending fractures and faults in the upper and outer part of the porphyry, and breccia mineralization occurred within a steep cryptoexplosive breccia pipe. The ore-related alteration typically consists of Na-Ca-Sr alteration and greisen. In order to understand the petrogenetic link between the Sn-polymetal mineralization and the host quartz porphyry, this paper presents new whole-rock geochemistry for the quartz porphyry, EPMA analysis of ore and gangue minerals, and in situ U-Pb dating of cassiterite. The Laser Abrasion Multiple Collector Inductively Coupled Plasma Mass Spectrometer (LA-MCICP-MS) cassiterite U-Pb dating yields two well-defined isochron ages of 138 ± 6 Ma for disseminated ore and 135 ± 6 Ma for the vein-type ore, which could be regarded as the ore-forming age. The cassiterite U-Pb ages (ca. 138–135 Ma) determined in this study, together with previous data, reveals the close temporal and genetic relationship between the mineralization event and the emplacement of the quartz porphyry. The quartz porphyry is characterized by high SiO2, Na2O, and A/CNK values (1.09–1.21). REE tetrad effect combined with extremely high Rb/Sr, K/Ba ratios and low K/Rb, Zr/Hf, La/Nb, La/Ta and Eu/Eu* ratios indicate that the quartz porphyry is a highly fractionated peraluminous I-type granite that is hydrothermally altered. Low eNd(t) values of 4.27–0.28 and the two-stage depleted mantle Nd model ages (T2DM = ca. 1279–908 Ma) for the quartz porphyry, are similar to granites in Precambrian microcontinents of the eastern part of the Central Asian Orogen (CAOB). This suggests that the quartz porphyry was derived from the remelting of juvenile crust and Precambrian rocks in an extensional setting. Therefore, the highly fractional crystallization and magmatic-hydrothermal interactions of the quartz porphyry have contributed to the formation of the Weilasituo Sn-polymetal deposit.

The Tianbaoshan Pb–Zn–Cu–Mo deposit is located in the eastern part of Jilin–Heilongjiang region, NE China which is considered to be the eastern segment of the Central Asian Orogenic Belt. Field and geochronological evidences indicate that this deposit experienced three types of mineralization including Hercynian skarn, cryptoexplosion breccia pipe, and Yanshanian quartz vein. The early stages of the Pb–Zn–Cu mineral systems in skarn and cryptoexplosion breccia pipe are characterized by a high-temperature, high-salinity H2O–CO2–NaCl system of hydrothermal fluids that were possibly exsolved from the Hercynian wall-rock granodiorite. These fluids show H–O isotopic compositions similar to those of typical magmatic fluids. By contrast, the low-temperature hydrothermal fluids of the later stages are represented by low-salinity NaCl–H2O systems with low H–O isotopic values. The skarn and cryptoexplosive breccia pipe types of Pb–Zn–Cu mineralization tend to have weakly negative δ34S values of − 4.0‰ to − 0.8‰ (mean values of − 2.31‰ and − 2.16‰, respectively), indicating that the sulfur was sourced from the Hercynian magma. Therefore, the early stage ore-forming fluids of the skarn and cryptoexplosive breccia pipe were most likely sourced from high-temperature and high-salinity fluids closely related to the cooling and fractional crystallization of the Hercynian granodiorite, while the later stages changed to NaCl–H2O meteoric water influx. Whereas the ore-forming fluids of the quartz vein type of Mo mineralization were high-temperature, high-salinity NaCl–H2O systems that differed from those of the skarn and cryptoexplosion breccia pipe, but their H–O isotopic compositions also indicate a magmatic fluid. The weakly enriched δ34S values of molybdenite from the quartz vein type Mo mineralization (δ34S = 0.2–2.8‰, average of 1.65‰) are comparable with those of other Mesozoic Yanshanian Mo deposits (δ34S = 0.4‰–4.1‰, with an average of 1.39‰–3.15‰), but differ significantly from those of the Hercynian Pb–Zn–Cu skarn and cryptoexplosion breccia pipe. This indicates that the sulfur of quartz vein type of Mo originated from Mesozoic Yanshanian magmatism and that the ore-forming fluids were derived from Yanshanian magmatic rocks rather than being a product of the Hercynian activity. The δ13C values of the fluid inclusions in quartz from the skarn, cryptoexplosion breccia pipe and quartz vein types are in a narrow range of − 19.5‰ to − 9.3‰, similar to those of the Shanxiuling Group, which indicates that the carbon of the three types of mineralization had the same primary origin in the Shanxiuling Group. The lead isotope compositions of ores from the skarn and cryptoexplosion breccia pipe types of mineralization (206Pb/204Pb = 18.0725–18.3627, 207Pb/204Pb = 15.3721–15.5694 and 208Pb/204Pb = 37.5542–38.8208) overlap with those of the Hercynian granodiorite and Shanxiuling Group marble, suggesting that the lead was probably derived from a mix of two different sources, the Shanxiuling Group and the Hercynian granodiorite. Whereas the lead isotope compositions of ores from the quartz vein type of Mo mineralization (206Pb/204Pb = 18.3837–18.6949, 207Pb/204Pb = 15.6824–15.7293 and 208Pb/204Pb = 39.1009–39.1889) are significantly higher than those of the Shanxiuling Group marble and the Hercynian granodiorite. This indicates that the lead may be a product of Yanshanian magmatic activity instead of the nearby Hercynian granodiorite.