Copper sulfide deposition and remobilisation triggered by non-magmatic fluid incursion in the single-intrusion Tongchang porphyry system, SE China

Porphyry ore deposits are a major source of base and precious metals. Likewise, they bear important fingerprints for understanding magmatic / hydrothermal processes in the convergent margin. For many decades, the sources of non-magmatic fluid and its role in sulfide mineralization in the porphyry hydrothermal systems have been equivocal. The Tongchang porphyry deposit, which is a single intrusive system with a well-established fluid history, is investigated to reconstruct its hydrothermal process that contributed to the ore formation. In-situ oxygen and strontium isotopes in hydrothermal quartz and anhydrite revealed a coexistence of magmatic and non-magmatic fluid reservoirs. The granodiorite—derived magmatic fluid and external groundwater were spatially separated by a hydrologically impermeable shell formed by retrograde mineral deposition (mainly quartz). The location of the impermeable shell coincided with a brittle-ductile transition (BDT) interface established in the host phyllite in response to latent heating by the cooling magmas. It is inferred that the ductile phyllite beneath the impermeable shell may have entrained some amounts of groundwater and remnant metamorphic fluid. The early fluid stage was dominated by the magmatic fluids, forming disseminated chalcopyrite and barren quartz veins in the potassic-altered ductile granodiorite at high temperatures (> 500 °C). The next stage (early-intermediate) was also driven by the circulation of the magmatic fluids, but in a largely brittle zone formed in-between the impermeable shell and the retreated BDT interface (similar to the so-called “carapace” in the orthomagmatic models). In this stage the formation of pyrite and chalcopyrite veins together with chloritic alteration at temperatures of 400–350 °C occurred. The late-intermediate stage was marked by incursion of the trapped non-magmatic fluids due to rupturing of the enlarged carapace. Mixing of the non-magmatic fluids and the magmatic fluids led to deposition of a major phase of vein-type Cu sulfide at temperatures of 350–300 °C. The late fluid stage was characterized by breaching of the impermeable shell in response to volumetric contraction of the fluid system, leading to excessive infiltration of groundwater and ore remobilization. Based on the Tongchang model, six generic fluid models are proposed for porphyry ore deposits that differ in availability of non-magmatic components as well as intrusive histories. The models can account for variabilities in ore and alteration styles found in porphyry ore deposits globally.


The Tongchang deposit
The Tongchang porphyry Cu deposit along with the Fujiawu and Zhushahong deposits are located in a Neoproterozoic orogen that sutured the Yangtze and Cathaysia blocks 34 .The three deposits, unlike most other porphyry deposits around the world, are associated with a single granodiorite porphyry intrusion 35 (Fig. 1a).The three granodioritic intrusions, intruded into the Neoproterozoic Shuangqiaoshan Group (mainly phyllite and tuffaceous slate), emanated from a common batholith at depth, derived from re-melting of subduction-modified lithosphere at ca. 170 Ma 34,36 (Fig. 1a).Over 95 vol.% of the magmatic rocks discovered at Dexing are granodiorite porphyries, with minor amounts of late diorite porphyry and aplite (U-Pb age ca.154 Ma 37 ).
Hydrothermal alteration and veins are comparable to the typical porphyry Cu deposits 5 .Potassic and propylitic alterations were developed in the granodiorite and wallrock (mainly phyllite), respectively, defining concentric zones around the granodiorites.These early-formed alterations were overprinted first by chlorite-sericite and then by sericitic alterations along granodiorite/wallrock boundaries and fractures/faults (Fig. 1b).Silicic alteration (silicification) has been documented in previous works 38 , but no discrete zones have been distinguished.Our field and petrography observation suggest that there are wide zones of silicification overprinting the propylitic alteration in the shallow levels and grading into the sericitic alteration at depths (Fig. 1c).Systematic mapping is needed to further constrain the extent and shape of the silicic zone.
Detailed SEM-CL petrography by Liu et al. 26 revealed six generations of quartz and four generations of anhydrite.Combining fluid inclusion and TitaniQ geothermometry, the authors also obtained formation temperatures for quartz.The CL textures and deposition temperatures are listed in the Table 2 and are briefly described below.The earliest quartz (Qz1) is characterized by mottled-CL texture (Fig. 2a) formed at 600-650 °C.The second quartz generation (Qz2) is characterized by an oscillatory core (Qz2a) and mottled rim (Qz2b), formed at 529-618 °C, and 473-551 °C, respectively.The third quartz generation (Qz3) commonly contains a dark interior (Qz3a) and oscillatory overgrowth (Qz3b) (Fig. 2b), and was formed at 374-392 °C and 350-450 °C, respectively.The fourth quartz generation (Qz4) is low in abundance and shows dark CL (Fig. 2a), and was formed at 310-390 °C.The fifth generation of quartz (Qz5) commonly consists of a dark core (Qz5a) and oscillatory overgrow (Qz5b) (Fig. 3a,b), which were formed at 356-360 °C and 344-351 °C, respectively.The latest quartz generation (Qz6) consists of dark to grey homogeneous domain (Qz6a) and very bright domain (Qz6b) (Fig. 3a), which were formed at 287-327 °C and 241-276 °C, respectively.
The first generation of anhydrite (Anh1) exhibits bright homogeneous to slightly patchy CL.It is subdivided to Anh1a and Anh1b according to CL intensity (Fig. 4a).The second generation (Anh2) has bright to grey CL with "wavy" oscillatory zoning (Fig. 4a).Anh2 is subdivided to brighter Anh2a and darker Anh2b.The third generation (Anh3) has euhedral morphology and display slightly oscillatory or homogeneous CL (Fig. 4a).The fourth generation (Anh4) is anhedral and CL-dark (Fig. 4b).All anhydrite types but Anh3 have been found in the A.V aq and B.V macpq and B.V cpq veins due to repeated vein reopening 26 , whereas Anh3 occurs only in the A.V aq vein in a minor amount.

Fluid sources
There were possibly three types of hydrothermal fluids in the Tongchang deposit based on previous H-O isotope studies.Bulk H-O isotopic analyses revealed the presence of magmatic fluid and groundwater, with the former one having δ 18 O values of 7.0-8.8‰and 87 Sr/ 86 Sr of 0.70455 29,30,35 , whereas the latter one having a δ 18   of − 8.2‰ 27,28 .In-situ O isotope analyses of this study also revealed a 18 O-depleted Qz3 (δ 18 O = 4.4‰, Fig. 3b), likely indicating precipitation from the groundwater that was circulating in the phyllite and slate.The host terrain was metamorphosed at greenschist conditions 34 , and the resultant metamorphic fluids had δ 18 O values of 10.4-11.2‰ 41.
The isotopic composition of these preexisting fluids can be modified by interacting with the host rock.Mass balance calculation suggests that groundwater can become 18 O-enriched at a temperature of 600 °C and water/ rock (w/r) ratio of 0.001(δ 18 O up to 13.0‰, Fig. 6b).Sr isotopes of the groundwater can approach that of the phyllite ( 87 Sr/ 86 Sr (170 Ma) = 0.71215) 22 .Similar w/r reactions may have occurred for the metamorphic fluid between the timing of metamorphism (ca.800 Ma) and ore formation (ca. 170 Ma).At temperatures above 300 °C, the metamorphic fluids can become 18 O-enriched and D-depleted, for instance, reaching a δ 18 O value of 13.0‰ at 600 °C and w/r of 0.01 (Fig. 6c).

Pinpointing non-magmatic components
Paragenetic relation and O-Sr isotope analyses suggest that the early and early-intermediate fluids have a common fluid source, pointing to a mixture of magmatic and non-magmatic fluids.The relative proportion of the magmatic and non-magmatic end-members depends on Sr content (denoted as [Sr] thereafter) of the two fluids.
For the early-, early-intermediate stage, 10 ppm [Sr] is assumed for the non-magmatic fluids according to an overview of global metamorphic fluids by Wagner et al. 42 .The same value is assumed for the magmatic fluids based on studies of the Butte and Bajo de la Alumbrera porphyry deposits 43,44 .A binary mixing model suggests  26 ).(b) A quartz grain consisted of brecciated core (might be Qz3) and euhedral Qz5b overgrow (the vein photograph was adapted from Liu et al. 26 ).The ellipses were the analytical spots with spot numbers.Noted that spots 6 & 7 in the Qz3 had low δ 18 O values (ca.4‰).The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).that Anh1, Anh2 and Anh3 predominantly comprise magmatic Sr (92%, 93% and 97%, respectively), and equivalently, 3% to 8% non-magmatic Sr (curve 1 in the Fig. 6a).Higher non-magmatic [Sr] values decrease the nonmagmatic proportion (curve 2 in the Fig. 6a), whereas higher magmatic [Sr] values up to 100 ppm increase the non-magmatic proportion to ca. 45% (curve 3 in the Fig. 6a).
For the late-intermediate stage (Qz4-Anh4), using [Sr] of magmatic fluid of the Butte porphyry deposit (ca.480 ppm 43 ) and 100 ppm [Sr] for non-magmatic fluid 45 , calculation suggests 43% of magmatic and 57% of non-magmatic component (curve 4 in the Fig. 6a).This estimation, if correct, would indicate a highly-evolved groundwater and/or metamorphic water (δ 18 O = 12‰) that requires w/r interaction at low ratios (< 0.01).A fluid process that is capable of generating this fluid is similar to one developed for the Bingham porphyry Cu deposit 16 .In that model, the authors recognized a deep exchange zone where small patches of groundwater  www.nature.com/scientificreports/became 18 O-enriched at high temperature and low w/r.These fluids were subsequently pumped to the deposition site at shallower levels where sulfide deposition and alteration occurred.The Qz5-precipitating fluids were most likely the evolved groundwater and metamorphic fluid according to the O isotope results (Fig. 5).This inference is also supported by other observations First, bulk-rock Sr isotope analyses suggest that sericitic altered porphyry have high 87 Sr/ 86 Sr (up to 0.709), indicating a dominance of phyllite-derived Sr (curve 5 in the Fig. 6a).Second, the large volume of sericitic alteration requires large volumes of fluids that cannot be provided by magmas already cooled to low temperatures around 350 °C46 .
The Qz6 exhibits high yet variable δ 18 O values with some being the highest in porphyry deposits (up to 27‰), corresponding to a parent fluid with high and variable δ 18 O values (from 9.4 to 17.1‰).This large spread in δ 18

Mechanisms of non-magmatic fluid incursion
The Sr mixing calculation revealed a decreasing trend in the proportion of non-magmatic components (from 8 to 3%) between the early and early-intermediate stages.The decreasing trend is compatible with a scenario where non-magmatic fluids are progressively consumed in a closed system.Formation mechanism of a closed system in porphyry environments was studied by Fournier 3 .The author demonstrated the formation of an impermeable shell in the host rock through retrograde precipitation of quartz surrounding the porphyry intrusion at temperatures between 400 and 350 °C.The heat dissipated from the magmas also changes the rheology and thus hydrology of the host rock, forming a brittle to ductile transition interface (BDT) separating an internal ductile/ lithostatic zone from an external brittle/hydrostatic zone.Interestingly, the BDT interface commonly coincides with the impermeable shell, and thus separates the internal magmatic fluids from the external groundwater.
Nevertheless, the Fournier model did not consider possible entrainment of residual metamorphic fluid in the internal zone, and thus cannot explain the high δ 18 O signatures of the late-intermediate stage of the Tongchang deposit.Additionally, the Fournier model was built on multi-intrusion systems, where heat dissipation took place cyclically as opposed to a monotonic cooling in the mono-intrusion Tongchang deposit.In a mono-intrusion system, monotonic cooling would cause the BDT interface to migrate downward continuously and, therefore, create an intermediate region between the impermeable zone and the retreated BDT (Fig. 7a,b).This intermediate region is similar to the so-called "carapace" in many other orthomagmatic models 47 .The carapace zone can be repeatedly ruptured due to overpressures from the underlying cupola.
The late-intermediate stage at Tongchang may have undergone a major rupturing of the intermediate region as evidenced by the brecciation in Anh4, while the impermeable shell remained intact.Rupturing of the carapace zone may have released the enclosed non-magmatic components (Fig. 7c).Subsequently at the late stage, magmatic fluid production may have significantly decreased so that fluid pressure inside the magmatic-hydrothermal region was greatly reduced, causing volumetric contraction and breach of the impermeable shell.The breach may have induced invasive infiltration of the external groundwaters.www.nature.com/scientificreports/

Establishing and extending the Tongchang model
A genetic model is proposed for the Tongchang porphyry deposit based on the understanding of fluid reservoirs and spatiotemporal evolution (Fig. 7d).Similar to orthomagmatic models 47 , it commences with the establishment of a magmatic cupola, where magmatic fluids are accumulated.This is followed by the formation and downward migration of the impermeable shell and BDT interface.The early and early-intermediate stages are dominated by magmatic fluids, which produced disseminated Cu sulfides through chemisorption reaction and potassic alteration 48 (Fig. 7a), succeeded with vein-type Cu sulfides through fluid cooling and chlorite-sericite alteration (Fig. 7b).The late-intermediate stage was marked by incursion of non-magmatic fluids (metamorphic fluid) and subsequent mixing with magmatic fluid.The dilute and cool non-magmatic fluid caused chalcopyrite deposition due to rapid destabilization of CuCl − 2 complexes 13 and increase of H 2 S activity 2,3 (Fig. 7c).The late stage was dominated by evolved groundwater, forming a high- sulfidation assemblage of pyrite and tennantite in the phyllic altered rocks (Fig. 7d).This is similar to the Butte porphyry deposit where deep protores (chalcopyrite-pyrite-magnetite) with potassic-chloritic alterations were remobilized by circulating oxidized groundwaters 49 .
The Tongchang model is further extended to account for variability in fluid availability of non-magmatic components and intrusive history (Fig. 8a).In porphyry deposits without non-magmatic fluids, such as those emplaced in contemporaneous volcanic and igneous rocks 50 , a thick impermeable shell cannot form due to a lack of external groundwater.Non-magmatic incursion would not happen, instead, such deposit would be dominated by magmatic fluids.Ore and alteration styles would resemble the early and early-intermediate stages of the Tongchang model, generating disseminated sulfides and chlorite-sericite alteration in the case of single intrusion (Fig. 8b), but potassic alteration in the case of multiple intrusions 49 (Fig. 8c).
In multi-stock systems involving non-magmatic fluids, common in most porphyry deposits 5 , three scenarios are distinguished depending on the spatial configuration of the intrusions and the resulting thermal history.If repeated magma intrusion maintains the BDT interface at a location close to the impermeable shell until mineralizing fluid is completely consumed (Fig. 8d), little non-magmatic incursion would happen so that ores would be dominated by high-temperature disseminated sulfides.These ores would be remobilized by external groundwater at low temperatures if the impermeable shell was breached.In contrast, if repeated magma intrusion occurred in a way that allowed incursion of entrained non-magmatic components (Fig. 8e), ores would resemble that of Tongchang, for instance, in the El Salvador deposit the pre-mineral intrusions acted merely as host rocks 52 .If repeated magma intrusion caused the impermeable shell to breach at high temperatures, magmatic fluids would surge out and displace external groundwater circulation (Fig. 8f).This scenario similar to the Fournier model would result in phreatic brecciation of the country rocks, and led to breccia-related mineralization at depths and epithermal mineralization atop.

Conclusion
Combined O and Sr isotope analyses provided new lines of evidence pointing to a transition from early magmatic-dominant to late non-magmatic dominant fluid system in the Tongchang mono-intrusion porphyry deposit.Non-magmatic components including isotopically evolved groundwater and metamorphic fluids were  28 ; metamorphic fluid values are from Zhao et al. 41 .The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).distinguished.The hydrological evolution of the deposit was largely controlled by dynamic interplay of the impermeable shell formed by retrograde mineral deposition and BDT interface.The initial non-magmatic incursion into the magmatic fluid promoted the major period of Cu sulfide deposition due to the diluting and cooling effects.The Tongchang model is applicable to mono-intrusion porphyry deposits where non-magmatic components are available.The Tongchang model is extended to six scenarios with broader implications.

Methods
Nine selected quartz vein samples cover all vein and alteration types.Guided by SEM-CL petrography, quartz is analyzed for oxygen isotope with secondary ion mass spectrometry (SIMS) and anhydrite is analyzed for Sr isotopes with multi-collector LA-ICP-MS.Water-rock interaction and mixing models are constructed based on O-Sr isotope data.

In-situ O isotope analyses
In-situ quartz oxygen isotopic compositions were measured using a Cameca IMS 1280 SIMS at the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS).A Cs + primary ion beam with an intensity of about 2 nA was accelerated at 10 kV and focused on an elliptic spot of ~ 10 × 20 µm in size.Oxygen isotopes were measured using multi-collection mode on two off-axis Faraday cups, with 16 O counts being typically 109 cps during the analytical session.Obtained 18 O/ 16 O ratios were normalized to the VSMOW waters ( 18 O/ 16 O = 0.0020052), and then corrected for instrumental mass fractionation using NBS-28 (δ 18 O VSMOW = 9.5‰ 51 ).A quartz standard (Qinghu, δ 18 O = 8.4 ± 0.2‰) was used to monitor instrumental drift.Measured δ 18 O values for Qinghu are between 8.3 and 9.1‰, with a mean of 8.6 ± 0.2 ‰ (1σ, n = 22).Analytical uncertainty for each analysis was normally better than 0.3-0.4‰(2σ).

In-situ Sr isotopes
Strontium isotopes in anhydrite were determined with a Neptune Plus MC-ICP-MS equipped with a MICRO/ Las Pro 193 nm ArF excimer laser ablation system at IGGCAS.Laser parameters were set at a repetition rate of 8 Hz, a fluence of 10 J/cm 2 , and 90-μm spot size.Ion signals of 83 Kr, 84 Sr, 85 Rb, 86 Sr, 87 Sr, and 88 Sr were monitored by six Faraday cups at low-resolution mode.Prior to analysis, the ICP-MS was tuned to a maximum sensitivity using a standard solution.Analytical runs started with measurement of Kr gas for 40 s with laser-off, followed by laser ablation for 60 s.A piece of shark tooth ( 87 Sr/ 86 Sr = 0.709179 ± 0.000007, 2σ) as the primary standard, and Slyudyanka apatite ( 87 Sr/ 86 Sr = 0.70766-0.70773)as the quality-check standard, were analyzed twice every ten unknowns 52 .Data reduction was conducted offline and potential isobaric interferences were resolved following the protocols described in Yang et al. 52 .Results of the Slyudyanka apatite suggested an analytical precision of ± 0.000113 (1σ) and accuracy of ± 0.000129.

Oxygen and Sr isotope modeling
Oxygen isotopic compositions of fluids in equilibrium with quartz were calculated with the following equations 51 : Water-rock interaction models were derived using the following mass-balance equation (See the Tab "Water-rock interaction modeling" in the Appendix) 53 : where C , w , i , r , f , and HO stands for wt.%H or O, water, initial value, phyllite, final value, and δD or δ 18 O.

Figure 1 .
Figure 1.(a) A geological map of the Dexing porphyry Cu district showing distribution of granodiorite (zircon U-Pb age ca.170 Ma) and diorite porphyries (zircon U-Pb age ca.154 Ma) intruding phyllite and slate (Pt3, Neoproterozoic) along with potassic, propylitic, chlorite-sericite, and sericitic alteration zones (adapted from Liu et al. 26 ); (b) A cross section profile of the ore district showing vertical distribution of rocks, alterations, and ores (adapted from Liu et al. 26 ).Locations of samples examined in this study and for whole-rock Sr isotope study by Jin et al. 27 are also shown; (c) A simplified column showing strong silicification in the phyllite and slate at shallow depths in drill core ZK821.The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).

Figure 3 .
Figure 3. Cathodoluminescences microtextures and O isotopic analyses of D.V pd veins hosted in a sericitic altered phyllite.(a) A profile traversing Qz3b, Qz5b, Qz6a and Qz6b revealed distinctive oxygen isotopic compositions (the CL image was adapted from Liu et al.26 ).(b) A quartz grain consisted of brecciated core (might be Qz3) and euhedral Qz5b overgrow (the vein photograph was adapted from Liu et al.26 ).The ellipses were the analytical spots with spot numbers.Noted that spots 6 & 7 in the Qz3 had low δ18 O values (ca.4‰).The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).

Figure 4 .
Figure 4. Cathodoluminescence microtextures and Sr isotopic analyses of anhydrite in A.V aq and B.V macpq veins in altered porphyry.(a) Four generations of anhydrite (Anh1 to Anh4) have distinctive CL and 87 Sr/ 86 Sr ratios (the vein photographs and CL images in the middle and upper right were adapted from Liu et al.26 ).Note that the Qz in the middle CL image contained two generations of quartz (Qz2 and Qz3), which is visible in Fig.7dof Liu et al.26 ; (b) The anhydrite (Anh4) intergrown with quartz (Qz4), pyrite (Py) and chalcopyrite (Cpy) had high 87 Sr/ 86 Sr ratios (the vein photographs were adapted from Liu et al.26 ).Note that the overexposed strips in the CL images were caused by presence of tiny carbonates that had very high CL responses.Yellow cycles were laser spots accompanied with 87 Sr/ 86 Sr values.The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).
value is possibly due to Rayleigh distillation.It is worth noting that quartz Qz6a contacting directly Qz5 shows δ18 O values close to that of Qz5 (Fig.3a), likely indicating that Qz5 and Qz6a precipitated from the same fluid.Assuming the isotopic composition of Qz5-deposit fluid as the starting composition for the Qz6-depositing fluid, Rayleigh distillation modeling can produce the O isotope signatures in the Qz6a and Qz6b by cooling from 250 to 205 °C and vapor loss up to 70% (Fig.6d).

Figure 6 .
Figure 6.(a) In-situ Sr isotopic compositions of anhydrite (Anh1 to Anh4) compared with the porphyry (Pp) 35 and phyllite (Pl) 27 .Also shown are modeled mixing curves between magmatic and non-magmatic fluids.(b) A fluid-rock interaction model for equilibrium fractionation between groundwater (G.W.) and phyllite.(c) A fluid-rock interaction model for equilibrium fractionation between metamorphic water (M.W.) and phyllite.(d) A Rayleigh distillation model showing O isotope fractionation during vapor loss between 340 and 250 °C.H-O isotope values of groundwater are from Zhang et al.28 ; metamorphic fluid values are from Zhao et al.41 .The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).

Figure 7 .
Figure 7.A genetic model for the formation of an impermeable shell and brittle/ductile transition (BDT) interface in the Tongchang porphyry Cu deposit.(a) In the early stage, retrograde precipitation of quartz formed a hydrologically impermeable shell, coinciding in space with the BDT interface.Non-magmatic components were trapped within the ductile phyllite.Disseminated chalcopyrite was formed by magmatic fluid reacting with mafic minerals in the porphyry.Early barren quartz veins were formed in fractures.(b) In the early-intermediate stage, the BDT moved downward, leaving behind a hydrostatic intermediate zone, which was ruptured upon fluid overpressures and formation of intermediate-temperature disseminated ores.(c) In the late-intermediate stage, the trapped non-magmatic components migrated upward and mixed with magmatic fluids, forming veintype Cu sulfides.(d) Magmatic fluid production came to an end and induced external groundwater infiltration and ore remobilization.The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).

δ 18 OFigure 8 .R
Figure 8. Six generic scenarios for porphyry ore formation, considering variabilities in non-magmatic availability (colored or grey background denoting with non-magmatic or without non-magmatic fluids) and intrusive history.(a) This scenario is the same as the Tongchang model.Ore style consists of intermediatetemperature ores, low-temperature ores, and remobilized ores.(b) and (c) represents mono-and multipleintrusion system without non-magmatic components.The former will be dominated by intermediate-T ores, whereas the latter dominated by high-T ores.(d-f) represents multi-intrusion system with non-magmatic components and variable thermal histories depending on spatial configuration of intrusions.Ore style varies accordingly.The figure was reproduced using CorelDRAW2019 (http:// www.corel draw.com/ en/).

Table 1 .
O value A summary of sampling locality and petrography of the analyzed rock samples of the Tongchang porphyry Cu deposit.

no. Sampling location Vein type Host rock alteration
The rock is significantly affected by chlorite-sericite alteration.Primary mafic minerals are replaced by chunks of chlorite, sericite, hematite, muscovite, and chalcopyrite.Feldspar phenocrysts are replaced by sericite.Quartz phenocrysts remain largely unaffected.Groundmass is replaced by fine-grained hematite and chalcopyrite.The rock is intensively crosscut by hematite quartz veins (V hq ), which are subsequently cut by chalcopyrite pyrite quartz veins and veinlets (V cpq ) The host rock is a diorite porphyry.Feldspars are completely replaced by sericite in the center and chlorite in the rim.Groundmass mainly consists of small biotite, sericite, and minor amounts of quartz The center of feldspar phenocryst is replaced by chlorite while rim is replaced by sericite.Primary mafic minerals are replaced by chlorite, rutile, chalcopyrite, hematite, and magnetite.Aggregations of chlorite-rutile-magnetite, chlorite-chalcopyrite-rutile-anhydrite are present.Groundmass consists of quartz, anhydrite, rutile, and muscovite.
mqp Feldspar phenocrysts are pseudomorphed by sericite.Mafic mineral pseudomorphs are not common.Where observed, they consist of chlorite and pyrite.The rock is intensely silicified.Quartz in the groundmass is medium-sized, intergrowing with abundant muscovite and chlorite.Sulfides are dominated by pyrite and occur as aggregations and bands 10DX220 Drill hole ZK8-4 601 m The immediate host rock consists of strong Sericitic alteration halos of the molybdenite quartz pyrite vein.In the halo, primary minerals except quartz are completely replaced by large muscovite, rutile, quartz, and pyrite.No mineral pseudomorphs are eliminated.Groundmass consists of fine-grained quartz and large muscovite 10DX140 Drill hole ZK0-2 337 m D.V pd The rock is a sericitic altered phyllite, consisting of oriented sericite, quartz, pyrite, and rutile 10DX145 Drill hole ZK4-4 410 m It is a sericitic altered phyllite, consisting of oriented sericite, quartz, pyrite, and rutile 10DX201 Drill hole ZK8-4 738 m It is a breccia consisting of pyrite, quartz, and carbonate

Table 2 .
A summary of generations, mineral assemblages, CL textures, and formation temperatures.

Table 3 .
In-situ O isotopes of hydrothermal quart of the Tongchang porphyry Cu deposit.

Table 4 .
In-situ Sr isotopes of hydrothermal anhydrite of the Tongchang porphyry Cu deposit.