Characteristics of Cu-Au-Bearing Quartz Veins at Danyore Valley Area, Kohistan Terrane, Northern Pakistan: Evidence from Geological, Geochemical, and Geochronological Studies

1. Introduction

Gold and copper association is reported in several ore deposits worldwide, including porphyry-style ore deposits, Iron Oxide Copper-Gold (IOCG) deposits, epithermal deposits, orogenic gold deposits, skarn deposits, and Volcanogenic Massive Sulfide (VMS) deposits. Porphyry-type deposits are one of the largest gold-copper reservoirs in the upper crust, accounting for over 100 tons of Au and 50% of the global copper resource reserves. These copper deposits primarily originated from low-temperature magmatic-hydrothermal fluids at shallow levels (<5 km depth) in continental and island-arc orogenic settings. It is generally acknowledged that gold can be removed from the porphyry–epithermal system by later hydrothermal fluids, which form Cu-Au-rich quartz veins surrounding the felsic intrusion bodies (Chiaradia, 2020; Garwin, 2019; Hou and Cook, 2009; Kerrich et al., 2000; Kesler et al., 2002; Sillitoe, 2010). Secondary copper staining (malachite, azurite, and chrysocolla minerals) and alteration assemblages (potassic, phyllic, argillic, and propylitic) in bedrock exposures are frequently observed in the vicinity of hydrothermal deposits; they are valuable indicators for prospecting (Ma et al., 2021; Raza et al., 2021; Zhang et al., 2019; Zhao et al., 2021).

Global geologists have collaborated for over a half-century to significantly advance our knowledge of geodynamic mechanisms and ore formation in various tectonic settings, including intraplate regions, continental rifts, and accretionary orogens (Arndt et al., 2005; Candela and Piccoli, 2005; Franklin et al., 2005; Goldfarb et al., 2005; Kerrich et al., 2005). However, a better comprehension of the metallogenesis of orogens originating from continent-to-continent collisions is needed; the formation of numerous giant deposits still needs to be more adequately understood. The surface of the Earth is known for having several mountain belts that formed during the collision of continents, such as the Variscan orogen in Western and Central Europe (Seltmann et al., 1994; Sibuet et al., 2004; Zhang, 1997), the Himalayan-Tibetan orogen in Asia (Yin et al., 2000).

The Himalayan-Tibetan orogen contains many hydrothermal-magmatic ore deposits (i.e., Pb-Zn deposits, porphyry copper deposits, orogenic Au deposits, Sn–W deposits.) (Seltmann et al., 1994; Yin et al., 2000; Zaw et al., 2007). It mainly comprises the Karakorum and Himalayas ranges in the south and the Tibetan plateau in the north. It involves several terranes such as Eastern kunlun-qaidam area, Ladakh-Kohistan arc terrane, Songpan-Ganzi-Hoh area, Qiangtang Terrane (500–600 km wide), and Lhasa Terrane (300 km wide) (Yin et al., 2000).

Ladakh-Kohistan arc terrane covers northern Pakistan and north-western India and is mostly composed of Precambrian basement units, Paleozoic to Cenozoic magmatic rocks, and sedimentary strata (Figure 1). Numerous geological, geochemical, and isotope studies (Miandad et al., 2014; Shah et al., 2012) had been carried out in the Kohistan terrane of northern Pakistan and several ore deposits and mineral occurrences were discovered, such as Copper-lead polymetallic veins deposits (Hussain et al., 2021; Hussain et al., 2023), rare earth elements (REE) mineralization in alkaline rocks (Hussain et al., 2020), placer gold deposits adjacent to the Indus River and its tributaries (Alam et al., 2019).

The Danyore Valley area is located in the Gilgit district at the central part of the Kohistan terrane (Figure 2). It is mainly covered by intrusive granitoid rocks of the Kohistan Batholith. Systematic geological studies relating to the geochemistry of granitoids and their tectonic settings are lacking in the literature. During our field investigations, large surface exposures of green-blue secondary copper stains were found in many places within the gabbro-diorite intrusion bodies of the Kohistan Batholith. In addition, significant hydrothermal quartz veins are recorded for the first time in the Danyore Valley prospect. These veins are characterized by Cu-Au-rich sulfide minerals, surrounded by pervasive alterations. Due to the lack of advanced geochemical data and isotope analyses, the characteristics of hydrothermal metallic ore veins and the geochemical signatures, age, and tectonic setting of the host granitoids are poorly understood. Selected samples were taken from gabbro, diorite host rock outcrops, and metal-bearing quartz veins. The intended outcomes of this research are (a) to constrain the age, tectonic setting, and petrogenesis of the wall rock units, (b) to identify the mineralization style and alteration patterns, and (c) to establish a magmatic-hydrothermal model for the area. In order to achieve the objectives of this work, fieldwork, microscopic observations, whole rock geochemistry (major, trace, and rare earth elements), mineral analysis, LA–ICP–MS zircon U–Pb age dating, and zircon trace elements are conducted to the collected samples from the Danyore Valley Cu-Au prospect. The findings of this study address an enormous research gap relating to the Mesozoic magmatism of the Kohistan Batholith and suggest that the Danyore Valley prospect is a potential porphyry-style/vein-type hydrothermal Cu-Au mineralization, which indicates that further geological and geochemical prospecting research is needed.

2. Geological Background

2.1. Regional Geology

Pakistan has a prominent position in the field of geology owing to its diverse geological features. It encompasses three significant tectonic plates, namely the Eurasian, Indian, and Arabian plates (Molnar et al., 1975). Numerous ore deposits have been documented within the Tethys domain (Figure 1a). These include the porphyry copper (Cu) and gold (Au) deposits in Chaghi and Rekodeq, placer gold deposits in northern areas (Alam et al., 2023); gold (Au) mineralization attributed to sulfide occurrences in the Chitral region known as Awireth-Krinj (Ahmad et al., 2018) and veins-type gold (Au) deposits in the Artsan area of Chitral (Calkins et al., 1981).

The geological formations across Pakistan exhibit considerable variations from one region to another, displaying different rock types that span various ages. During the pre-Cretaceous era, approximately 110 million years ago, the Indian landmass was still undergoing significant tectonic activity, exhibiting geological folding alongside the African continent. According to several studies (Bignold, 2003; Coward et al., 1987; Khan et al., 1993; Searle et al., 1987), a collision/obduction between the Asian and Indian plates happened in the Early Tertiary and Late Cretaceous periods (with the Indian continent at ~60–50 Ma; with the Eurasian continent at 54–34 Ma). Jagoutz et al. (2009) stated that the calc-alkaline Matum Das intrusion indicates the initial stage of subduction. During the Late Cenozoic period (∼45 Ma), the Eurasian and Indian plates encountered, forming substantial mountain chains, such as Karakorum, Hindukush, and Himalayan ranges (Kazmi and Jan, 1997). Two volcanic arc belts are present in north Pakistan, namely the Chaghi and Kohistan arc belts (Bukhari et al., 2010). The Tethyan suture zones of the Himalayas (Figure 1) were used to divide the north Pakistan region into three major blocks: the Karakoram block, the Indo-Pakistan plate, and the Kohistan island arc block (Robertson and Collins, 2002).

The Karakoram block originated in the late Permian–Triassic period on the southern margin of the Asian tectonic plate. The Karakorum Fault separates the Karakorum block from southern Tibet (Zanchi et al., 2011). The major constituents of the Karakoram Block are high-grade metamorphic rocks, consisting mainly of dolomitic marbles, clinopyroxene amphibolites, interlayered sillimanite-grade pelites, and kyanite with garnet (Rolland et al., 2009).

The Indo-Pakistan plate's interaction with the Asian plate triggered the stress, which resulted in the subduction of the Tethys oceanic crust along the Karakoram Suture, which led to the formation of the Karakoram Range. Subsequent stress events caused the Tethys sea plate to subduct under the Kohistan-Ladakh belt alongside the Northern Indus Suture, leading to the formation of the Kohistan-Ladakh magmatic arc (Petterson et al., 1985; Searle et al., 1987; Tahirkheli, 1979). At approximately 68 Ma, the Indo-Pakistan tectonic plate and the Afghan block preliminary were encountered during the Late Cretaceous period. Also, the Indus suture has experienced significant development through the obduction of ophiolites (Malkani et al., 2019).

Kohistan Island Arc block (also called Kohistan terrane or Kohistan complex, Figure 1) is surrounded by Afghanistan to the west, China to the north, and India to the east (Virdi, 1987). The island arc of this terrane is formed during the Cretaceous time (approximately during the period from 120 to 80 Ma) resulting from the intraoceanic diminution (Neo-Tethys ocean) (Shah and Shervais, 1999). The Kohistan Island Arc is situated within north of Pakistan, particularly in the Kohistan region, and continues into the parts of Gilgit-Baltistan and is parted from the Asian plate by the main Karakorum thrust fault (Shyok suture zone) (Jan and Tahirkheli, 1979), and from the Indian plate by main mantle thrust fault (Indus suture zone) (Petterson et al., 1985; Searle et al., 1999). Generally, the Kohistan region is often categorized into three main complexes: Giligit Complex, Chilas Complex, and Southern Plutonic Complex.

2.1.1. Gilgit Complex

(a) Volcano-sedimentary succession includes Teru/Shamaran Volcanic Formation and Dir Volcanics Group. Teru/Shamaran Volcanic is composed of rhyolites, ignimbrites, and volcaniclastics (silicic) found discordantly on a batholith-volcanic basement. The Dir Volcanics has two sections: the bottom one is chiefly comprised of turbiditic sandstones and siltstones with small limestone outcrops, while the upper part has volcanic breccias, sandstones, mudstones, ignimbrites, and rhyolites which have been trespassed by the younger Utror volcanics (Danishwar et al., 2001; Shah and Shervais, 1999; Sullivan, 1992; Tahirkheli, 1979).

(b) Yasin sedimentary Group has several exposures of volcanic sets, consisting of agglomerates, tuffs, and lavas. They principally contain patches of fossiliferous, massive, and shaly limestones. Sandstone layers are also found in some places. Based on the evidence from sedimentary sequences, the sedimentary layers of the Yasin Group were probably deposited during the Aptian-Albian age (i.e., early Cretaceous time) when the intra-oceanic Kohistan island arc was formed (Pudsey, 1986; Tahirkheli and Jan, 1984).

(c) Kohistan Batholith is characterized by intraoceanic and continental magmatism with ages ranging from 112–42 Ma. This huge igneous body intruded into the Juglot and Chalt Volcanic Group to the north and south. Kohistan batholith contains multiple types of lithologies, mainly plutonic rocks consisting of granites, diorite, gabbroic diorite, and gabbroic (Bignold et al., 2006; Coward et al., 1987; Petterson et al., 1985)

2.1.2. Chilas Complex

The Chilas complex is an extensive exposure of intrusive body (Hamidullah and Jan, 1986; Khan et al., 1993), primarily calc-alkaline plutonic rocks with composition ranging from mafic to ultramafic (Bignold et al., 2006). Diorites and gabbronorites dominate the complex, while gabbros, mafic dykes, troctolites, peridotite, anorthosite, and dunites constitute minor components (Khan Tehseenullah et al., 1996). This complex's ages ranged between 84+0.5 Ma of U–Pb zircon age dating (Zeitler and Chamberlain, 1991) and 69.5+9.3 Ma of Sm-Nd isotope dating (Yamamoto and Nakamura, 2000).

2.1.3. Southern Plutonic Complex

(a) Jijal complex: It consists of ultramafic rocks, including harzburgites, websterites, dunites, norites, pyroxenites, garnet granulites, amphibolites, and hornblendites (Jan and Howie, 1981; Tahirkheli et al., 2012). These rock units ages range from 91.8+1.4 Ma (U–Pb zircon dating) (Schaltegger et al., 2002) to 117+7 Ma (Sm-Nd isotopes analysis) (Dhuime et al., 2007).

(b) Kamila Amphibolite: the amphibolite from this rock unit is chiefly composed of plutonic rocks (diorites, gabbros and norites) and metavolcanic (mostly basaltic andesites and basalts). Other lithologies are granites, tonalites, diorites, garnet quartzites and calc-silicates, anorthosites, hornblendites, and hornblende schists (Jan, 1990; Shah and Shervais, 1999). According to Anczkiewicz (2000), the age of the Kamila Amphibolite is 95 to 100 Ma.

2.2. Local Geology

The Kohistan Batholith is a main intrusive complex in northern Pakistan (Figure 1b), forming part of the Trans-Himalayan Batholith. Kohistan Batholith spans approximately two hundred and seventy kilometers from west to east. The batholith covers 168 miles from its eastern extent, starting with the Nanga Parbat Haramosh Massive (NPHM) and extending westward to the Shyok Suture Zone (SSZ). Additionally, it has a width of 34 miles and a north-south dimension ranging from 50 to 60 km, making up a substantial portion of the twenty seven hundred kilometers long Trans-Himalayan Batholith (THB) (Petterson et al., 1985).

The Kohistan Batholith developed in four major magmatic phases: (a) the first phase is composed of foliated gabbro-diorites, Matum Das tonalite, and deformed intrusive rocks of 102 Ma; (b) the second event undeformed gabbros and gabbro-diorites igneous bodies which were generated around 80-60 Ma; (c) the third stage emplaces granites and granodiorites with the age of 60-40 Ma, (d) the younger phase includes granite and leucogranite sheets which formed around 50-24 Ma (Bignold et al., 2006; Heuberger et al., 2007; Petterson et al., 1985; Treloar et al., 1989). Most of these intrusions are volumetric plutons ranging from modest to massive, with significant vertical and horizontal orientation, with several dikes, sills, sheets, and lopoliths also reported (Khan et al., 1998; Khan Tehseenullah et al., 1996; Treloar et al., 1996).

The Danyore Valley area lies in the Gilgit district, within the Kohistan plutonic Batholith of the Kohistan Arc belt (Figure 2). It is situated approximately 13 kilometers northwest of Gilgit City (Northern Pakistan) (Figure 3). Chilas is positioned southwest of the research area, while Utror and Chalt (also known as Dir, Shamran, Juglot, and Yasin) are situated in the north side of research (Khan et al., 1993). Geological characteristics of the research area include gabbro, gabbro-diorite, diorite, and granite bodies. The collected hand specimens from these rock units display that the mineral assemblages are dominantly massive, medium to coarse-grained quartz, plagioclase, mica, potash feldspar, and calcite (Figure 3 and Figure 4).

During the current research investigation, the outcrops of gabbro and diorite bodies (Figure 4a–c) generally exhibit a greenish-to-blue shade due to the presence of minerals that contain copper, primarily malachite and azurite. On the surface, which can easily be identified on hand specimens (Figure 4d–h). Furthermore, Cu-Au occurrences have been recognized for the first time in many places within the study area. The mineralization mainly comprises a stockwork of fractures, veins, and veinlets with NW and NE orientations (Figure 4c). The host rocks display features like silicification and biotite alterations, and they are essentially related to the presence of mineralized quartz veins.

2.2.1. Petrography Characteristics of the Host Units

The diorite rocks of the Danyore Valley area consist of essential minerals such as plagioclase (41%), quartz (36%), and biotite (7%), with a minor amount of muscovite (5%). The accessory minerals are mainly represented by epidote (2%), calcite (3%), and opaque (1%) minerals (Figure 4d–g). The coalescence of smaller sub-grains frequently causes the larger quartz grains to show patchy extinction (Figure 4e). The prismatic euhedral crystal grains of plagioclase have lengths of up to 200 μm and widths of 80 μm. They can be identified by lamellar twinning, particularly in the center of crystals, which has substantially changed to sericite and epidote (Figure 4g). Some quartz grains have a strong, barely wavy extinction and are mixed in with elongated calcite grains. Biotites at the edges of quartz grains are primarily medium-grained subhedral to euhedral crystals that form irregularly. This suggests that some alteration may have happened to these rocks after they were formed. Muscovite is anhedral to subhedral and has parallel-oriented crystals, creating the strips. Iron oxides and sulfide minerals are considered as opaque minerals (Figure 4g). They can be spotted within the plagioclase crystals and along the cracks as inclusions.

On the other hand, the petrographic observation of the Danyore Valley gabbro (Figure 4h,i) indicates the presence of plagioclase (44%) and biotite (38%) as major constituents, while some hornblende (8%), muscovite (5%), chlorite and opaque (2%) minerals occur as minor components. The majority of biotite and hornblende completely changed into iron oxides and chlorite. Many plagioclase crystals are partially or entirely altered to sericites and epidotes. Biotite can be observed as small to medium-sized, highly evolved flakes that show prominent light brown to dark brown pleochroism. It is predominantly correlated to opaque minerals, chlorite, and occasionally muscovite. Green to dark green pleochroism can be observed in chlorite. Its close affiliation with biotite indicates that it was formed by alteration. Some biotite grains are partially changed to chlorite, and some are entirely converted to chlorite minerals (Figure 4i). The topotaxial growth of biotite can be observed by the presence of chlorite along cleavages in some of the slightly changed grains. Muscovite tends to appear in flakes and tabular-shaped crystals around the plagioclase and quartz.

3. Sampling and Analytical Methods

A total of 90 samples from wall rocks and sulfide-bearing quartz veins were obtained from the study area (Figure 3) during three field trips (2021-2022). Twenty-five samples were selected for thin sections for petrographic studies, and 17 polished thin sections were selected for ore microscopic investigations and to carry out an electron probe microanalysis (EPMA) analysis. Four samples from the study area (host rocks) and three from the previous study (Heuberger et al., 2007) were selected for whole-rock geochemical analysis. Five samples from the wall rocks were selected for geochronology studies to investigate the age of host units. The supplementary data material (SDM I) provides the analytical methodologies procedures.

4. Results

4.1. Zircon U–Pb Geochronology

Laser ablation ICP-MS U-Pb analysis and obtained ages for the studied zircons from the Danyore Valley prospect are presented in the supplementary data table (SDT I). 182 spots were selected during geochronological studies. Forty points were obtained on zircon mineral grains from each diorite specimen (SD-1, SD-5, SD-6, and HD-1) and twenty-two spots from the gabbro sample (SD-9). Cathodoluminescence images (CL; Figure 5) were utilized for point selection for the trace element studies (SDT II) to assess the internal structure and outer appearance (morphology) of the specimens. Generally, zircon grains from studied gabbro and diorite samples are brassy yellow to light yellow and mostly anhedral to subhedral crystals that were fractured amidst the ascending of metamorphism or magma and alteration activity, which causes the zircon breakdown (Ayonta Kenne et al., 2021). CL reveals zircon crystals with sizes ranging from large (>210 μm) to short (<60 μm), displaying prismatic and pyramid shapes. However, no clear concentric zonation is observed, as shown in Figure 5.

In sample SD-1 (Diorite), the zircons display prismatic and pyramidal crystal appearances, which vary from euhedral to subhedral, ranging in size between 90 to 190 μm. The measured axial ratios are 1:1 and 2:2. Some grains have weak growth zoning with darker centres (Figure 5a). For the age analysis, twenty-six zircon spots yielded a concordia age of 111.60 ± 0.90 Ma, with a mean square weighted deviation (MSWD) of 0.41 (Figure 6a). The overall average age for the sample SD-1 is reported as 111.60 ± 0.90 Ma with an MSWD of 0.58 (Figure 6a). The 14 remaining grains, showing mild to moderate discordance were removed from the analysis due to substantial evidence of lead loss and metamictization.

The majority of zircons from sample SD-5 (Diorite) lack distinct zoning, although some have distinct clear zoning, and precise prismatic and pyramidal shapes, while other crystals appear colourless. Their size ranges from 60 to 210 μm, and their shapes are particularly euhedral to subhedral (Figure 5b). Thirty-nine of forty zircon spots recorded a concordia age of 112.18 ± 0.74 Ma (MSWD = 0.17). The sample's cumulative mean age is 111.26 ± 0.72 Ma (MSWD = 0.56; Figure 6b).

In sample SD-6 (Diorite), the presence of fluid or mineral inclusions, alteration, and metamorphism suggested a lack of clear zoning in studied zircon crystals. (Ayonta Kenne et al., 2021). The crystal structures of zircons vary from euhedral to subhedral, ranging in size between 90 to 190 μm, and axial ratios of 1:1 and 2:2 (Figure 5c). Thirty-nine spot analysis reported a concordia age of 111.64 ± 0.73 Ma (MSWD = 0.92). The sample SD-6 total mean age is 111.64 ± 0.73 Ma (MSWD = 0.55; Figure 6c).

The analyzed zircons crystal grains of Sample HD-1 (Diorite) predominantly exhibit a dark colour, while some are colourless. Clear pyramid or prismatic shapes are not easily distinguishable in the cathodoluminescence (CL) micrographs of most zircon crystal in the sample. The zircons have euhedral to subhedral shapes and range in size from 90 to 190 μm (Figure 5d). In terms of the age analysis, the Concordia age of thirty of the forty zircon spots showed 112.17 ± 0.81 Ma (MSWD = 0.072). The sample's average age of this sample is 110.81 ± 0.81 Ma (MSWD = 0.074).

Zircon grains in sample SD-9 (Gabbro) lack clear zoning in CL photographs; most grains appear black. Zircon crystals have a size ranging from 60 to 210 μm. (Figure 5e). During age calculation analysis, twenty zircon analyses yielded a concordia age of 110.21 ± 0.99 Ma (MSWD = 0.98). The sample's mean age is 110.57 ± 0.99 Ma (MSWD = 0.35; Figure 7b).

4.2. Zircon Geochemistry

The results of the trace element analyses (i.e., Y, Nb, Ti, Ta, HF, Pb, U, Th, and REE) are given in SDT (II). The zircons chondrite-normalized REE patterns from the Danyore Valley area of Kohistan Batholith are depleted in HREEs and enriched in LREEs (Figure 8), with prominent positive Ce anomalies and moderate negative Eu anomalies, confirming that the zircons are magmatic (Bao et al., 2014; Hoskin et al., 2003; Rubatto et al., 2017).

The Eu/Eu* and Ce*/Ce* values for diorite rocks range from 0.22 to 1.51 and 53.89 to 1581.32. For the SD-9 gabbro rock, the values are 0.2 to 0.63 and 4.67 to 640.28, respectively (SDT II). There are profound variations in trace element concentrations within the same sample for zircons. Hafnium values, which are relatively higher in host rocks (diorite and gabbro) samples, range from 4732.78 to 10851.98 ppm, with an average of 7405.99 ppm. Niobium (Nb) and Tantalum (Ta) have a low content in all samples (diorites and gabbro), with abundances ranging from 0.83 to 18.93 ppm (avg. 3.88 ppm) and 0.11 to 2.63 ppm (avg. 0.51).

In summary, the zircon crystals display an extraordinary composition characterized by elevated concentrations of Thorium (Th), Uranium (U), Hafnium, and Yttrium (Y) alongside notably low levels of Tantalum (Ta) and Niobium (Nb). Furthermore, the Th/U ratio of studied grains indicates values of Th/U >1 (SDT II), confirming the magmatic signatures of the studied wall rocks (Hoskin et al., 2003).

4.3. Major, Trace, and Rare Earth Elements (REE)

Four specimens from the current research (one gabbro and three diorites) were chosen for whole-rock geochemical analysis. Additionally, three diorite samples from the previous research (Heuberger et al., 2007) were added to the analysis to assess the potential origin of the parental magma and the tectonic environment of the studied area. The current research's analyzed sample results and relevant geochemical attributes from the reference data (Heuberger et al., 2007), are given in SDT III.

4.3.1. Diorite

The results of major oxides for diorite wall rock display intermediate to a high content of SiO₂ (53.55 to 66.20 wt.%), intermediate to high Al₂O₃ (avg. 17.68 wt.%), Na₂O (avg. 6.14 wt.%), (avg. CaO 2.69 wt.%), (avg. Fe₂O₃ 1.88 wt.%), low MgO content (0.93 to 3.52 wt.%), P₂O₅ (avg. 0.12 wt.%), TiO₂ (avg. 0.32 wt.%), and LOI (avg. 2.50 wt.%) (SDT III). These geochemical features indicate that the paternal magma is andesitic to basaltic nature (Tahirkheli et al., 2012). According to an AFM (Na₂O + K₂O- FeOT - MgO) diagram, the analyzed diorites fall within the calc-alkaline category (Figure 9a). On the diagram by (Frost and McCammon, 2008), the granitoids from Danyore Valley appear to have magnesian characteristics (Figure 9b). Based on the A/CNK vs A/NK plot, the studied diorites are metaluminous in characteristics, except for one sample that was plotted on peraluminous (Figure 9c). The analyzed diorites exhibit significant similarities in major oxide composition to those found in the Kohistan batholith (Petterson et al., 1985).

The investigated dioritic rock displays varying concentrations of Ni (1.73 ppm), Cr (10 ppm), and Co (4.40 ppm). High field strength elements (HFSEs), including Nb (7.93 ppm), U (4.82 ppm), Ta (0.31 ppm), Hf (3.83 ppm), and Th (17.32 ppm), exhibit depleted levels, with Zr being the exception, showing a slightly more comprehensive range at 146 ppm (SDT III). Conversely, the significant ion lithophile elements (LILEs) exhibit notable concentrations, with Ba at 260 ppm, Rb at 38.83 ppm, and Sr at 617 ppm. The spider-normalized diagrams of Danyore Valley diorites (Boynton, 1984; McDonough and Sun, 1995) possess fragmented trace element structures with lower HREE and elevated LREE element concentrations.

4.3.2. Gabbro

The studied gabbro rock expresses a limited extent of SiO₂ (43.22 wt.%), low MgO (8.97 wt.%), Na₂O (2.23 wt.%), and K₂O (6.08 wt.%). Similarly, low TiO₂ (1.11 wt.%), P₂O₅ (0.20 wt.%), and a moderate range of Al₂O₃ (17.68 wt.%), CaO (5.32 wt.%), and Fe₂O₃ (5.47 wt.%) (SDT III). The LOI value of gabbro rock is 4.31 wt.%. According to the classification graph of alkali-total iron magnesium (AFM) (Irvine and Baragar, 1971), the gabbro rocks predominantly belong to the calc-alkaline category (Figure 9a). Based on the diagram A/CNK vs A/NK (Shand, 1942), the studied gabbros are metaluminous (Figure 9b).

The studied gabbro rock is illustrated by varying concentrations of Co (12.6 ppm), Cr (470 ppm), and Ni (132 ppm). Concentrations of high field strength elements (HFSE) include Ta (0.60 ppm), Nb (8.8 ppm), U (1.61 ppm), Hf (2.4 ppm), Th (1.71 ppm), and Zr (110 ppm). Conversely, large ion lithophile elements (LILEs) have substantial concentrations (Sr = 577 ppm, Ba = 300 ppm, and Rb = 144 ppm). The normalized primitive mantle and REE chondrite behaviors are distinguished by the enrichment of LILE-LREE compared to the decreased HFSE and HREE (Figure 10a,b). The normalized patterns show significant positive deviations in Rb, Pb, and P (Figure 10a). The rare earth element (REE) distribution in the gabbro samples demonstrates a marginal rightward trend, and there are noticeable dips in Eu with weak negative anomaly (Figure 10b).

4.4. Mineralization Style and Sulfide Chemistry

In the Danyore Valley area, mineralization predominantly occurs in association with sulfide-rich quartz veins and extensive alteration assemblages (Figure 11a–c). The orientation of the veins is predominantly NW, although some veins exhibit NE trends. The outcrops of Cu-Au mineralization are visible at over 35 different locations (Figure 11a,d,g,j). They appear as either discontinuous horizontal to vertical quartz veins, sulfide-rich quartz veins, or less commonly massive ore. The mineralized masses have a dimensions ranging from 1 to 5.5 meters, with inconsistent lengths ranging from 14 to over 900 meters.

A significant portion of quartz veins exhibits notable abundance in primary sulfide minerals, including chalcopyrite and pyrite grains, which can be clearly observed in the field and collected hand specimens (Figure 11b). Microscopically, chalcopyrite, pyrite (Figure 11f–i), and bornite are the major components of the quartz veins rich in sulfides (Figure 11l). The most prevalent sulfide mineral is chalcopyrite, which is preceded by pyrite, sphalerite, and bornite in decreasing abundance in the Danyore Valley area. A summary of the paragenetic correlations associated with ore minerals and alteration assemblages is given in Figure 12. The EPMA results for the selected minerals (i.e., chalcopyrite, pyrite, and bornite) are presented in SDT IV.

Chalcopyrite is the predominant mineral found in sulfide-rich quartz veins. It is typically correlated with sphalerite, bornite, and pyrite, the latter usually forming a ring around the major sulfides (Figure 11c,f,l). Chalcopyrite predominantly interacts with silicate minerals and coarse-textured euhedral quartz. It can be distinguished by euhedral or subhedral and irregularly distributed grains/textures. Chalcopyrite commonly forms continuous bands that vary from 500 μm to 5 mm thick. Furthermore, it frequently occurs with sphalerite as chalcopyrite illness. It is primarily interlocked with sphalerite, covellite and bornite, it is often altered by the secondary minerals bornite and covellite across its outer edges. The S and Fe Average concentrations in the chalcopyrite are 33.54 to 53.96 and 29.99 to 46.97 (avg 37.86 & 33.30 wt%), the Cu and Au concentrations are 0.008 to 35.62 wt% and 30 to 1230 ppm (avg 34.73 wt.% & 324 ppm) (SDT IV). The chalcopyrite mineral has also been analyzed for As, Se, Si, Pb, Ag, Zn, Ni, Mn, Te, Sb, Te, and Cd. Average trace element Concentration of Se 264, As 196, Ag 134, and Te 294 ppm, Pb 0.037, Zn 0.035, Ni 0.013, Mn 0.010, Sb 0.012, and Cd 0.023, while Si showed concentration below the detection limit.

Pyrite is the most frequently occurring mineral encountered in quartz veins rich in sulfides, pyrite outgrows sphalerite and is being witnessed forming massive euhedral to subhedral cubic grains and rhomboidal crystals along to cracks (Figure 11d–f). The pyrite crystals have a grain size ranging from 50 μm to 6 mm. It mostly appears with euhedral to subhedral crystals of quartz and infrequently occurs with other sulfides. Most of the pyrite grains show similar contents of S 52.32 to 53.96 (avg. 53.17 wt.%) and Fe 46.14 to 46.93 (avg. 46.5 wt.%) in comparison with their reference concentrations (Farhan et al., 2023) (S = 53.45 wt.% and Fe = 46.55 wt.%) (SDT IV). Trace elements average contents above the detection limit, such as Se 106, As 138, Au 250, Ag 25, and Te 444 ppm, whereas Ni 0.014, Sb 0.005, Si, Mn 0.012, Zn 0.023, and Cd 0.028 wt%. Cu, Si, and Pb are undetectable in all investigated grains (SDT IV).

In large chalcopyrite grains, boronite has been found sporadically and as oriented mineral exsolution flakes, mainly found in association with quartz veins rich in copper (Figure 11k,l). Bornite crystals have a grain size ranging from 10 μm to 2 mm. Chemically, bornite is nearly equimolar, the Cu, S, and Fe concentrations (wt%) are 58.54 to 63.81, 24.99 to 28.19, and 11.21 to 12.68 (Avg. 62.44, 25.97, and 11.70) (SDT IV). Trace elements concentrations above the detection limit are As 330, Se 473, Au 220, Ag 683, and Te 217 ppm, Zn 0.036, Mn 0.007, and Cd 0.013, while Si, Pb, Sb and Ni showed concentrations below the detection limit.

The mineralized quartz veins are located primarily within the altered diorites and gabbros. The boundary between the mineralized region and the adjacent country rock is distinct and accurate, sometimes showing a gradual transition in some places within the study area.

The supergene enrichment assemblage is extensive and is characterized by the presence of large exposure (up to 1-1.5 meters in length) of carbonate copper minerals. They comprise azurite, malachite, chrysocolla, and native copper (Figure 11g-j). These areas are surrounded by high iron-rich gossan materials, consisting of limonite, hematite, and goethite minerals (Figure 11k). It is most likely that post-depositional activities significantly participated in the liberation, transportation, and redeposition of Cu that had probably been extracted from a hidden ore body or pre-existing country rocks. The primary gangue materials include calcite, biotite, and quartz, along with a small percentage of muscovite and feldspar.

4.5. Alteration Assemblages

Hydrothermal alterations appear close to the sheared zones and along the boundary among the wall rock and quartz veins containing sulfides. (Figure 4 and Figure 11). The sulfide-quartz veins are locally surrounding by three pertinent hydrothermal alterations: propylitic, phyllic, and carbonatization assemblages. Among them, propylitic and phyllic alteration are specifically essential for the mineralization process. These alterations patterns typically appear within a range of about 1 to 3 meters away from mineralized masses, displaying a vein-like distribution, particularly evident in close proximity to the veins. The most frequently encountered hydrothermal gangue minerals are quartz and calcite.

4.5.1. Phyllic Alteration

This type of alteration appears in the outer part, at the interface with the host rock (diorite and gabbro). It is identified by the assemblage of sericite + quartz + pyrite. Sulfide-bearing quartz vein is occasionally covered and surrounded by a small parallel muscovite layer (Figure 13a). The microscopic studies reveal that the feldspars of country rocks are typically replaced by sericite and clay minerals (Figure 13b). Sericitization assemblage is composed of subhedral to anhedral sericite with a fine to medium grain size and microcrystalline quartz (Figure 13a). The presence of sericite in fine-grained quartz would have been attributed to silicification, which is the release of silica during plagioclase sericitization. Therefore, sericite and quartz are frequently formed together. (Figure 13a–c).

4.5.2. Propylitic Alteration

This kind of mineralogical aggregate consists of biotite, chlorite, epidote, muscovite, and pyrite with a minor amount of carbonate minerals (e.g., calcite) and bornite. Host rocks close to the mineralized area are relatively altered and contain some disseminated and sulfide stringers, which possess geometric connectivity to quartz veins. All grains of sulfide are euhedral without post-formation changes. Microscopic observation indicates that the biotites were replaced by chlorite and epidote (Figure 13g). Chlorite is mainly recognized as a predominant mineralogical phase commonly resulting from the alteration of hornblende and biotite.

In some places along the Danyore Valley area, the propylitic alteration is generally appeared as unevenly distributed to the pre-ore alteration minerals and sulfide-rich veins (Figure 13i). More specifically, a substantial quantity of quartz, biotite, and epidote assemblages dominate the epidotization alteration. These minerals represent sequential patterns or aligning appearances in any scenario and they have subhedral to anhedral fine grains. The altered felsic granitoids are primarily crosscut by the later phase of calcite veins. (Figure 13e).

4.5.3. Carbonatization Alteration

Carbonatization is occasionally observed away from the mineralized area. The carbonate-quartz region is primarily constituted of sterile quartz and calcite formed in the later stages. Most calcite grains are slightly altered and associated with a minor amount of apatite mineral (Figure 13e). Many euhedral quartz crystals indicate that the growth of hydrothermal ore-forming fluids lessened and was subsequently terminated.

5. Discussion

5.1. Age of Gabbro-Diorite Intrusion from Danyore Valley Area

In general, earlier workers (Auden, 1935; Burg et al., 2006; Griesbach, 1893; McMahon, 1884; Treloar et al., 1989; Wadia, 1928) attempted to determine the ages of the diorites and gabbros from Kohistan Batholith on the basis of structural behaviors, xenolith composition, petrological Imprints, and field correlations. However, the need for accurate geochronology indicates significant uncertainties regarding the timing of the emplacement of these granitoid bodies. (Treloar et al., 1989) initiated the Ar-Ar dating on the Matum Das Pluton (81 Ma) and Naz Bar Pluton (granite 84 Ma, diorite 82 Ma, and granodiorite 80 Ma) in the Kohistan Batholith. Furthermore, according to the tectonic map of the north of Pakistan, neighboring areas of northern Ladakh, and western Tibet by Zanchi et al. (2011), the age of the calc-alkaline gabbro-diorite units of the Kohistan Batholith is 110 to 90 Ma (Rb-Sr dating). The Kohistan batholith's age of granodiorite and granite rocks is 85 to 40 Ma, by the K-Ar and Rb/Sr dating methods (Treloar et al., 1989). Diorites from Shunji pluton and Pingal pluton (Kohistan Batholith) located approximately 101 km from my study area given an age of 64.5 ± 0.5 Ma and 41.0 ± 0.5 Ma based on the U-Pb zircon dating technique (Khan et al., 2009).

Five intrusive rock samples collected from the Danyore Valley region (Kohistan Batholith) were dated utilizing the LA-ICPMS zircon U-Pb age dating technique. (SDT I and Figure 5, Figure 6 and Figure 7). The U-Pb isotopic analysis of studied zircons from the diorite specimens provided a concordia age of 111.60 ± 0.90 Ma (MSWD = 0.41) to 112.18 ± 0.74 Ma (MSWD = 0.17) (Figure 5 and Figure 6). Correspondingly, the gabbro rock sample (SD-9) displayed a concordia age of 110.21 ± 0.99 Ma (MSWD = 0.98). The crystallization age of studied gabbro-diorite units from the Danyore Valley area is largely in agreement with those reported from the Gawuch Village area (Kohistan batholith), situated approximately 227 km northwest of Gilgit. The gabbro and diorite rocks from this area give an age range between 106.7 and 107.2 Ma according to the U-Pb age dating system (Heuberger et al., 2007).

5.2. Tectonic Setting of Gabbro-Diorite Intrusion

There is a debate in the literature about the tectonic context of the Kohistan Batholith, ranging from a continental rift environment (Petterson, 2010) to an island arc setting (Petterson et al., 1991). Besides, some researchers (Treloar et al., 1989; Treloar et al., 1996) contend that the batholith is an instance of magmatism associated with subduction. In contrast, others (Petterson et al., 1985; Searle et al., 1987) have argued that it originates from magmatism originating from continent collisions. However, the Kohistan Batholith is probably the product of the subduction and collision of tectonic plates (Searle et al., 1999). Samples taken from the Kohistan Batholith showed that it represented a continental arc arising from the downward movement of the Indian plate below the Eurasian plate (Searle et al., 1987).

Generally, zircons from continental crust and ocean crust are distinguished using the proposed discrimination diagram of (Grimes et al., 2007). The U/Yb vs Hf, tectonic setting classification diagram predominantly illustrates that the zircons from the researched area fall within the continental zircon domain (Figure 14c), revealing the continental nature of these rocks. On the other hand, there is a dispute regarding which sources originated massive amounts of post-collisional calc-alkaline, predominantly mafic magmas, from which the analyzed zircons formed (Petterson et al., 1991). Several theories propose that these magmas emerged from partially melting either subducted oceanic crust or from the anatexis of earlier island arc crust (Ashraf, 1999). The Sm versus Gd/Yb discrimination plot is usually used to identify the origin of zircon from different tectonic settings based on its trace element content (Grimes et al., 2007). It displays that all analyzed zircons from the Danyore Valley copper prospect have been mainly positioned outside the fields of an arc and a MORB environment, suggesting the continental origin (Figure 14d). Considering the likely association of the study area's diorites with the Gawuch formation in Chitral, which has an age of 110-112 Ma, proposed that these rocks originated in a continental margin tectonic environment (Heuberger et al., 2007).

Identifying the genetic type of granitoids from whole rock geochemistry is crucial for comprehending the evolution, magma sources, and tectonic settings (Pearce et al., 1984; Sylvester, 1998). According to Zr against 10,000 Ga/Al and Ce versus 10,000 Ga/Al discrimination graph (Figure 15a), granitoids from the Danyore Valley prospect fall within S- and I-type granites.

On the tectonic discriminant diagram, the diorites and gabbro from the study area primarily lie on the "volcanic arc granite (VAG)" field, as observed in the Ta+Yb against Rb plot (Figure 15c). Additionally, based on the Yb vs Ta tectonic graph (Pearce et al., 1984), the analyzed granitoid rocks are plotted within the volcanic arc area, with one specimen identified in the syn-collisional granite region (Figure 15d). Spider graphs of the primitive mantle to normalized compositions suggest that gabbros and diorites exhibit depletion in High Field Strength Elements (HFSE), including Eu, Li, Ti, and P, along with enhancement in Large Ion Lithophile Elements (LILE), in particular U and Ba (Figure 10a,b).

The Zr-Nb (ppm) ratio has the potential to indicate mantle depletion or enrichment, as suggested by (Geng et al., 2011). Analysis results from the Danyore Valley diorites and gabbros position within the depleted mantle field (Figure 15b), this depletion pattern suggests similarities to certain island arc basalts. The investigated gabbro and diorite specimens are most likely products of a partially melted or depleting asthenospheric mantle that has undergone metasomatism due to subduction-related fluids. Furthermore, the tectonic setting of the Danyore Valley granitoids is mainly consistent with the geodynamic environment of gabbro-diorite of the Kohistan Batholith, which primarily generated in a subduction-related environment (Jagoutz et al., 2009; Petterson et al., 1985).

To sum up, the host rock units of the Danyore Valley copper prospect predominantly plot within the continental arc field and have calc-alkaline signature with arc-like geochemical features.

5.3. Petrogenesis of Danyore Valley Intrusion

The granitoids from the Danyore Valley area of Kohistan Batholith are identified as calc-alkaline, I-type granitoids, comprising diorites and gabbro. The diminution of high field-strength elements (HFSE): Ta and Nb Figure 10a) is a typical geochemical feature of arc magma generated in the subduction zone (McCulloch et al., 1991), This observation further supports the integral supra-subduction area classification of the Kohistan Batholith, as initially proposed by (Tahirkheli, 1979). Studied diorites exhibit high SiO₂, medium to high K calc-alkaline, metaluminous properties, and possess relatively elevated sodium contents (Na₂O = 2.23–6.61 wt.%, with a mean concentration of 6.14 wt.%). These features suggest that the granitoids of Danyore Valley are typically identical to I-type granite characteristics (Chappell et al., 1992).

The high aluminum with andesitic magma nature is evident in the examined diorites. This type of magma is commonly generated in subduction-related environments, especially at continental edges (Wilson, 1989). Gabbroic rocks may originate from either Arid or moist basaltic magma during a mechanism of fractionated crystallization (Gaetani et al., 1998). The samples exhibit generally comparable trends on normalized-primitive mantle trace element graphs (Figure 10a,b), demonstrating large-ion lithophile elements (LILE) enrichment and notable reductions in Ti, Nb and Ta. These characteristics are typical of magmas associated with arcs (Briqueu et al., 1984; Brown et al., 1984; Gill et al., 1981). Gabbros and diorites show comparable compositions regarding Rare Earth Elements (REE) and trace elements. They also demonstrate comparable chondrite normalized REE distribution trends, with only slight variations in total amount and Eu/Eu* ratios. These similarities suggest a common source for both rock types and imply an evolutionary familial relation.

The studied rock samples display a calc-alkaline pattern, as illustrated in (Figure 9a) and show variations in SiO₂ ranging from 45% to 66%. Also, there is a lesser content in K₂O, MgO, and TiO₂, and an increase in Al₂O₃, CaO, FeO, and Na₂O suggesting a fractionation trend. Gabbros and diorites demonstrate high concentrations in Rb, Ba, U, and LREE relevant to K, Zr, Ti, Y, and HREE, indicating an arc-like geochemical signature. These trends in geochemistry indicates that the primary magma source of the studied plutonic rocks from the Danyore Valley area is generated from the fractional melting of depleted upper mantle source, which is enriched in LREE elements, followed by a fractionation crystallization process during their ascent through the mantle/crust and final emplacement. It is highly harmonic with the proposed formation model of granitoids from Kohistan Batholith by Petterson et al. (1985).

Detectable amounts of high-field strength element (HFSE) were found in all of the analyzed zircons. Ti, Nb, and Ta contents are less than 75 ppm, 62 ppm, and 3 ppm, respectively, suggesting a typically average abundance of magmatic zircons (Faisal et al., 2020; Hoskin et al., 2003). Conversely, magmatic and hydrothermal zircons could be distinguished by using binary diagrams of Hoskin (2005); Kirkland et al. (2015). Based on the data shown in the La against (Sm/La)_N graphs (Figure 14a), the majority of the investigated specimens from the Danyore Valley area had low La and high (Sm/La)_N, which is the characteristic of unchanged magmatic zircons (Grimes et al., 2009; Hoskin, 2005). Some grains plotted between the neo-crystallized hydrothermal zone and magmatic field, indicating that these grains may have undergone subsequently hydrothermal alteration and recrystallization after the gabbro-diorite emplacement.

La (N) versus Hf (Figure 14b) plot illustrates the excessive of LREE in the dated zircons. LREE (La and Pr) typically have sub-ppm to ppm-range absolute overages in igneous zircon, However, Ce abundances may reach up to about 50 ppm, which is considerably more compatible with magmatic zircons (Schaltegger et al., 2009). All examined zircons from the Danyore Valley prospect are plotted within the normal range of igneous zircon abundance in the Hf vs. La discrimination diagram (Figure 14b), confirming the magmatic origin for these zircon grains.

Monitoring changes in oxidation state during magma differentiation can be achieved by studying the trace elements of zircon. It is widely accepted that the impact of mineral crystallization on the abundances of Ce and Eu depletion is dependent on the state of oxidation (Hoskin et al., 2003; Trail et al., 2012; Xia et al., 2011). Therefore, the oxygen fugacity of the magma is often associated with the oxidation phase of rocks. In their comparably low LREE patterns, the zircons displayed substantial positive Ce anomalies, while Eu anomalies are mainly negative. Discremination diagram of Hf vs. Ce/Ce* (Figure 14e) shows that most zircons fall within the restricted spectrum of oxygen volatility with increasing magma growth (elevated Hf), suggesting that relatively reduced settings (low oxygen fugacity) which were employed for the initial crystallization.

For identifying the oxidation state at the magma formation, the Ce/Ce* vs Eu/Eu* (Figure 14f) diagram is an invaluable resource (Trail et al., 2012). Variations in the anomalies of Ce and Au may be understood as indications of the physiochemical crystallization process of zircon. Zircon possesses distinctive properties in its Rare Earth Element (REE) pattern. (Ballard et al., 2002; Barth and Wooden, 2010; Burnham and Berry, 2012; Claiborne et al., 2010; Li et al., 2014; Pettke et al., 2005; Trail et al., 2012; Trail et al., 2011). The recent application of Ce and Eu contents in zircons for oxybarometry is due to their sensitivity to magmatic oxidation states, driven by their ionic states. The degree of negative Eu anomaly can be influenced by the redox condition during the formation minerals from a hydrothermal fluid or molten substance. (Hoskin et al., 2003; Trail et al., 2012; Xia et al., 2011). Most zircons from the units under investigation exhibited an inverse relationship tendency when approaching to the oxidation phases. The Eu-anomaly noticed in this research is considered to originated from the Eu-deficient melt subjected to reduced environments due to the unfavorable incorporation of Eu2+ into the zircon lattice system (Trail et al., 2012).

5.4. Cu-Au Mineralization of Danyore Valley and Implications for Future Exploration

The composition of chalcopyrite in any particular ore system is primarily dependent on the existence or non-existence of various other co-crystallizing sulfides (George et al., 2016). Chalcopyrite exhibits crystallization within a body-centered tetragonal lattice system, where copper, sulfur (S), and iron (Fe) atoms are arranged in tetrahedral coordination (Li et al., 2013; Mikhlin et al., 2005; Todd et al., 2003). Previous studies (Cabri et al., 1985; Harris et al., 1992) have documented that chalcopyrite expresses extraordinary compatibility with solid solutions of Au and Ag. Numerous previous studies have highlighted the favorable hosting capabilities of chalcopyrite for various trace elements incorporated into its structure. Due to this characteristic, the trace element chemistry of chalcopyrite is a valuable tool for interpreting the formation of hydrothermal liquids in various geological settings (Barker et al., 2009; Farhan et al., 2023; Ingham et al., 2014). In the context of chalcopyrite lattice, elements including Ag, As, Co, Au, Ni, Pb, Se, Te, and S can potentially replace S and Fe atoms (George et al., 2015; George et al., 2017). Silver (Ag), gold (Au), arsenic (As), and selenium (Se) are commonly documented as trace components forming solid solutions within the chalcopyrite structure. Conversely, elements such as indium (In), thallium (Ti), gallium (Ga), and mercury (Hg) are rarely mentioned (Brill, 1989; Demir, 2008; Demir et al., 2013; George et al., 2018; Helmy et al., 2013; Huston et al., 2010; Moggi et al., 2002; Reich et al., 2020; Sadati et al., 2016; Wang et al., 2016).

Similarly, the analyzed chalcopyrites from Danyore Valley prospect host significant contents of As, Ag, Au, Cd, Sb, and Te elements, whereas Ti, Ga, Hg, and In are rare or below the detection limit. Gold (Au) was the dominant trace element discovered in the studied chalcopyrite grains, with some individual grains having notable concentrations up to 1200 parts per million. Other metals are commonly present at > 400 ppm.

The integration of trace elements like Fe, Ag, Au, Cu, and Zn into the chalcopyrite composition is more intricate compared to the other typical base-metal sulfides (George et al., 2016). Selenium and Tellurium are important gold carriers because they are frequently found as trace minerals in various copper-gold deposits that mainly contain gold (Cepedal et al., 2006; Ciobanu et al., 2006; Hu et al., 2006; Novoselov et al., 2015; Plotinskaya et al., 2006; Scherbarth and Spry, 2006; Vikentyev and Petrology, 2006; Voudouris, 2010). There is an enormous positive association between Au and Se and Te (Figure 16a,b) implying the episode of Au-tellurides and selenides inclusions. Several studies (Cooke and McPhail, 2001; Seward, 1973) indicated that valuable metals were probably carried through tellurium components, shown by the strong interactions between Te, Ag, and Au (Figure 16c). In addition, Figure 16d,e demonstrate a solid positive relationship between Cu, Ag, and Au. Furthermore, the same relationship is noticed between Sb and Zn, Sb and Ag, As and Ag. Figures 16f–i suggest a moderate to strong correlation between Sb and Zn, and As and Au. In terms of a substantial positive affiliation between Te and Au contents, the Danyore Valley chalcopyrite is closely similar to Kaldom Gol chalcopyrite (Farhan et al., 2023) and the Cayeli deposit Turkey chalcopyrite (Revan et al., 2014).

Based on the fieldwork and microscopic studies, two types of veins have been discovered in the research area (Figure 17). The initial one is mineralized quartz veins which contain high concentrations of sulfides, surrounded by different types of alteration assemblages including chlorite, muscovite, biotite, and sericite (Figure 17a,b). The second one is late-stage barren calcite veins, which intruded on the early-stage preexisting mineralized quartz veins. This type is primarily associated with the carbonatization process (Figure 17c). The tectonic and structural setting of the region played an essential role in their formation. The gabbro-diorite host units were deformed and several cracks, fractures, and fault plans were formed within the wall rock body that allowed the metal-bearing fluids to ascend (Figure 17a,b). The ascending hydrothermal fluids rich in sulfides, filled these structure with undeformed quartz veins. Secondary carbonate minerals (i.e., malachite) and hydrothermal alterations (biotite-muscovite-chlorite-sericite zone) are formed close to these veins. A new calcic hydrothermal solution (rich in carbonate minerals) intrudes into the preexisting quartz veins. As a result, a barren calcite vein is formed, which mainly involves sulfide and quartz grains (Figure 17c).

The high assemblages of base and valuable metals in the analyzed specimens from Danyore Valley associated with the significant exposure of copper enrichment patterns and the field's alteration zones can be used as clues for further geological, geochemical, and geophysical studies and prospecting. The scarcity of detailed geological, structural, and geochemical data and advanced isotope analyses in the literature underscores the need for more comprehensive studies. The primary knowledge gained from the current research can serve as a foundation for understanding the Northern Pakistan region's broader geological and tectonic context and the Kohistan Batholith specifically. In addition, further mineral exploration and subsequent mining activities in the Kohistan Batholith can provide substantial economic opportunities for local communities in Northern Pakistan.

6. Conclusions

The Danyore Valley area, which is located in the Kohistan Batholith, hosts several mineralized quartz veins associated with gabbro-diorite intrusions. The host bodies of Danyore Valley consist mainly of diorites and gabbros which intruded during the Early Cretaceous period (∼110 Ma).

The primary magma source for the diorites and gabbros of the Danyore Valley area was derived from a depleted mantle that experienced partial metasomatization due to fluids originating from subducted slabs. The wall rock units of Danyore Valley Cu-Au prospect are most likely formed in a continental margin environment and from the same magma through fractional crystallization.

The mineralization style is characterized by sulfide-bearing quartz veins which are principally enriched in copper and gold and surrounded by sericitization, chloritization, and carbonatization. The alteration zones, sulfide mineral chemistry, and ore assemblage and textures suggested an intermediate sulfidation epithermal type of mineralization.

Future geological studies in the Danyore Valley and surrounding areas should focus on gaining a deeper understanding of the region's geological processes, mineralization mechanisms, and geodynamic history.