Deep Exploration Porphyry Molybdenum Deposit in Dasuji, Inner Mongolia: Insight from Aeromagnetism and Controlled-Source Audio-Magnetotellurics

Abstract

Porphyry molybdenum deposits hold significant potential for deep exploration. However, in the Dasuji molybdenum deposit, quartz porphyry, granite porphyry, and syenogranite are sporadically exposed beneath low mountains and hilly terrain, limiting the effectiveness of traditional geological methods. Consequently, geophysical techniques have become essential in this region. This study provides new magnetism and resistivity data obtained through high-precision aeromagnetic surveys and controlled-source audio-magnetotellurics (CSAMT) profiles. These results reveal concealed deep porphyries, identify deep-seated molybdenum ore bodies, and establish a porphyry-type molybdenum metallogenic model. The porphyries exhibit the lowest magnetic values (about −200 to 370 nT), suggesting that molybdenum mineralization-related granitoids have exceeded the Curie temperature and undergone an intense magnetic weakening effect. Ferromagnetic or ferromagnetic substances have transformed into paramagnetic substances. The CSAMT results indicate that the mineralized granite porphyry generally has medium to high resistivity (300 Ω·m to 500 Ω·m) and dips southward with a 60° inclination angle. Additionally, an unclosed low-resistance anomaly in the deep region of site 0 indicates promising potential for further mineral exploration and the discovery of deeper mineralized porphyries. We interpret weak magnetic anomalies and variations in resistivity as caused by high crystallization temperatures, low oxygen fugacity, and hydrothermal alteration in the context of porphyry molybdenum deposit mineralization.

1. Introduction

Porphyry molybdenum deposits, closely associated with intermediate to acidic porphyry bodies in terms of time, space, and origin, represent the most significant source of molybdenum, accounting for 95% of the global supply [1,2]. Numerous studies on molybdenum deposits have emerged from Inner Mongolia [3,4,5]. Traditionally, the Tailong–Liangcheng fault-uplift zone was regarded as a blind spot for exploring large metal deposits due to its low mountains and hilly terrain [6]. However, with the rapid advancements in geological and geophysical exploration techniques, substantial molybdenum deposits have been successively discovered in Dasuji, Caosiyao, and Quanzigo [6]. This has elevated the region to the third-largest molybdenum ore belt in China, following the Lesser Khingan Mountains and Zhang Guangcai Ridge molybdenum ore belts. Geochronological and geochemistrical data suggest that the ore-bearing granite porphyry in Dasuji is primarily I-type granitoid [5,6]. Studies on micro-thermometry, fluid inclusions, and other mineral chemistry suggest that the Dasuji porphyry molybdenum deposit has undergone four developmental stages: (1) K-feldspar with minor molybdenum mineralization, (2) molybdenum mineralization associated with silicification, (3) lead–zinc mineralization accompanied by carbonatization and fluorination, and (4) non-mineralization. Despite these findings, questions remain about the metallogenic mechanisms and potential for deep mineral exploration [6]. For example, the physical and chemical conditions for molybdenum ore formation are not well understood, and the potential for further exploration in peripheral and deep regions remains a topic of debate.

Compared to the numerous geochemical and geochronological studies focusing on the Tailong–Liangcheng fault-uplift zone, relatively few studies have explored the geophysical aspects of the Dasuji porphyry molybdenum deposit. Traditionally, the induced polarization (IP) method is combined with controlled-source audio-magnetotellurics (CSAMT) for ore body detection [7,8,9]. The long-offset transient electromagnetic method (LOTEM) has been applied to geophysical investigations of the Earth’s crust [10,11,12,13,14,15,16]. Aeromagnetic surveys can be very useful for regional-scale generation of porphyry copper deposits and for constraining the planar distribution of magmatic rocks. Additionally, ground electromagnetic methods are effective tools for identifying supergene copper mineralization. Hypogene porphyry systems, characterized by clay- and silica-rich advanced argillic alteration, can be detected by their high resistivity [17,18,19,20,21].

This study introduces the latest large-scale, high-precision magnetic data to identify the quartz porphyry, granite porphyry, syenite granite, plagioclase granite, and diorite porphyry veins. Furthermore, CSAMT data are presented to elucidate the spatial distribution of deep-seated molybdenum ore bodies.

2. Geological Setting

2.1. Regional Geological Setting

Inner Mongolia hosts three molybdenum mineralization periods: Triassic, Jurassic, and Early Cretaceous. The earliest ore formation is closely linked to the evolution of the Paleo-Asian Ocean; and occurred during post-collisional extension [22] (Figure 1). The Dasuji molybdenum deposit is located in the northeastern part of the Khondalite Belt, which is formed around 1.95 Ga due to the collision of the Yinshan and Ordos Blocks (Figure 2a). The region’s stratigraphy includes the Paleoarchean Xinghe Group, Middle Archean Jining Group and Ula Mountain Groups, Neoarchean Serteng Group, Paleozoic Huaigou Group, and Mesozoic and Cenozoic strata. The Xinghe Group mainly consists of banded perilla plagioclase granulite, two-pyroxene granulite, and plagioclase amphibolite. The Jining Group is widespread across Zhuozi, Liangcheng, Jining, and Xinghe with prevalent lithologies such as leptite, granulite, and gneiss. The Ula Mountain Group primarily comprises gneiss, plagioclase amphibolite, and diopside marble. The Serteng Group mainly includes quartz rock, granulite, schist, and diopside marble. The Huaigou Group is mainly dominated by conglomerate, sandstone, and shale, representing Middle Jurassic clastic formations. The upper Jurassic Manketoubo Group contains terrestrial volcanic rocks. The lower Cretaceous Lisangou and Bainvpan Groups comprise terrestrial clastic and volcanic rocks, respectively. Cenozoic strata are prevalent in the central low-lying basin [5]. The region is characterized by significant fault activity, volcanic processes, and magma events. Three major west-to-east faults dominate the area, namely the Guyang–Wuchuan–Shangyi fault (F1), Linhe–Baotou–Jining fault (F2), and Daihai–Huangqihai fault (F3). Additionally, the north–south-trending Shangdu–Xinghe–Weixian fault (F4) plays a critical role. Mesozoic volcanic and intrusive rock distributions are influenced by these fault systems. Mineralization is closely associated with faults F3 and F4, which directly control the distribution of Mesozoic volcanic and intrusive rocks [22,23] (Figure 2b).

2.2. Geological Setting of Dasuji Molybdenum Deposit

The exposed strata at the Dasuji molybdenum deposit include Precambrian Jining Group gneiss, Tertiary shale, and Quaternary loess. Magmatic rocks in the area mainly consist of Late Archean fragmented plagioclase granite, Triassic quartz porphyry, granite porphyry, alkaline granite, Jurassic granite porphyry, and a minor diabase and diorite porphyry veins. Among these, the Triassic granite and quartz porphyry are closely associated with molybdenum mineralization [6] (Figure 3).

Triassic quartz porphyry is gray-white, with porphyritic and blocky structures. It comprises quartz (80%) with minor potassium feldspar (10%) and plagioclase (10%). This rock intruded Archean plagioclase granite as small stocks or veins, producing strong iron–manganese staining (resembling burned skin), and forming early molybdenum ore bodies. Granite porphyry is flesh-red, with spotted and blocky structures. Its phenocrysts consist of quartz (30%), potassium feldspar (30%), and a small amount of plagioclase (5%–10%). This rock intruded quartz porphyry, creating rupture zones and forming the main molybdenum ore bodies [6] (Figure 4).

The porphyry evolved through distinct stages: early potassium mineralization, middle sericite mineralization, and late kaolin and carbonate mineralization. Molybdenum ore bodies are mainly located at the top or within the contact zones between quartz porphyry and syenogranite (or syenogranite porphyry). These ore bodies are tightly controlled by sericite alteration and typically occur as lens-shaped formations, predominantly displaying micrograin-disseminated and veinlet-disseminated structures.

2.3. Petrophysical Parameters of Dasuji Molybdenum Deposit

Significant differences in petrophysical parameters are a prerequisite for geophysical surveying and research.

Table 1. Petrophysical parameters of core samples in No. zk 101, Dasuji molybdenum deposit.

Lithology	Drilling Depth	Length	Area	I	U	ρ	K
	(m)	(mm)	(mm2)	(μA)	(mV)	(Ω·m)	(10−5 SI)
Quartz porphyry	4.50	12	23.74	20	12,517.57	1238.20	7.54
Quartz porphyry	5.00	18	23.74	16	12,567.67	1035.96	8.80
Quartz porphyry	7.65	13	23.74	17	12,552.34	1348.38	5.03
Quartz porphyry	7.85	15	23.74	13	12,615.83	1535.90	15.08
Quartz porphyry	8.45	16	23.74	18	12,538.54	1033.56	6.28
Quartz porphyry	8.65	15	23.74	9	12,675.16	2228.95	10.05
Quartz porphyry	9.05	15	23.74	12	12,621.08	1664.58	18.85
Quartz porphyry	10.45	9	23.74	19	12,521.62	1738.38	11.31
Ore-bearing quartz porphyry	12.55	16	23.74	24	12,481.51	771.64	2.51
Ore-bearing granite porphyry	39.70	14	23.74	38	12,362.76	551.68	32.67
Alkaline granite	43.55	17	23.74	7	12,776.35	2548.83	16.34
Alkaline granite	45.80	10	23.74	19	12,523.01	1564.72	40.21
Alkaline granite	121.35	10	23.74	14	12,586.20	2134.26	18.85
Alkaline granite	122.15	14	23.74	13	12,584.46	1641.51	21.36
Alkaline granite	122.30	11	23.74	16	12,599.47	1699.50	30.16
Plagioclase granite	230.30	18	23.74	26	12,445.88	631.34	541.59
Plagioclase granite	231.10	20	23.74	68	12,170.51	212.45	625.79
Plagioclase granite	231.35	20	23.74	19	12,520.37	782.19	412.16

lists the petrophysical parameters, including specific resistivity and magnetic susceptibility, where I represents the supply current, U represents the supply voltage, and ρ and K denote resistivity and magnetic susceptibility, respectively.

Core samples, ranging from shallow to deep, consist of quartz porphyry, ore-bearing quartz porphyry, ore-bearing granite porphyry, alkaline granite, and plagioclase granite. Measurements were conducted using the water immersion method. Porphyry as a whole exhibited high specific resistivity (1016.62 Ω·m to 2548.82 Ω·m) and relatively low magnetic susceptibility (5.03 × 10⁻⁵ SI to 40.21 × 10⁻⁵ SI). Ore-bearing quartz porphyry and ore-bearing granite porphyry were characterized by moderately high specific resistivity (551.68 Ω·m to 755.90 Ω·m) and low magnetic susceptibility (2.51 × 10⁻⁵ SI to 32.67 × 10⁻⁵ SI). In contrast, plagioclase granite exhibited low specific resistivity (212.45 Ω·m to 782.19 Ω·m) and high magnetic susceptibility (412.16 × 10⁻⁵ SI to 782.19 × 10⁻⁵ SI).

3. Geophysical Analytical Methods

This study used aeromagnetic and CSAMT geophysical methods.

Table 2. Key survey parameters for the aeromagnetic and CSAMT methods.

Method	Key Parameter	Company	Measurement Range	Measurement Points	Spatial Resolution
Aeromagnetism	Total magnetic field	Danian, China	10 km2	222,811	0.1 m × 50 m
CSAMT	Apparent resistivity	Phoenix, Canada	1000 m	20	50 m

presents and compares the specific parameters of these two geophysical instruments for clarity.

3.1. Aeromagnetic Survey

This aeromagnetic system consists of five components: a quadcopter unmanned aerial vehicle, an airborne navigation and positioning system, an airborne aeromagnetic survey system, ground station instruments, and a ground-based post-processed kinematic differential base station (Figure 5) [25]. The aeromagnetic survey included evaluations for flight altitude quality, deviation distance, static noise level, dynamic noise level, and compensation accuracy. The dynamic noise level before compensation was ±14.13 nano teslas (nT), which was reduced to ±1.17 nT after compensation. Similarly, the standard deviation before compensation was ±16.58 nT, which was improved to ±1.18 nT after compensation.

The normal field calculation was performed using the International Geomagnetic Reference Field (IGRF) formula published by the International Association for Geomagnetism and Aeronomy (IAGA). The three components of the total geomagnetic field strength are defined as follows:

$$\mathrm{X}(t)={\displaystyle \frac{1}{r}}{\displaystyle \frac{\partial u}{\partial \theta }}={\displaystyle \sum _{n=1}^{n-N}{\displaystyle \sum _{m=0}^{m-n}{(\frac{a}{r})}^{n+2}\left[g_n^m(t)\cos m\lambda +h_n^m(t)\sin m\lambda \right]}}\times {\displaystyle \frac{d}{d\theta }}{P}_n^m(\cos \theta )$$

(1)

$$\mathrm{Y}(t)={\displaystyle \frac{-1}{r\sin \theta }}{\displaystyle \frac{\partial u}{\partial \lambda }}={\displaystyle \sum _{n=1}^{n-N}{\displaystyle \sum _{m=0}^{m-n}{(\frac{a}{r})}^{n+2}•\frac{m}{\sin \theta }\left[g_n^m(t)\sin m\lambda -h_n^m(t)\cos m\lambda \right]}}{P}_n^m(\cos \theta )$$

(2)

$$Z(t)={\displaystyle \frac{\partial u}{\partial r}}={\displaystyle \sum _{n=1}^{n-N}{\displaystyle \sum _{m=0}^{m-n}-(n+1)•{(\frac{a}{r})}^{n+2}\left[g_n^m(t)\cos m\lambda +h_n^m(t)\sin m\lambda \right]}}{P}_n^m(\cos \theta )$$

(3)

where u represents the geomagnetic potential, and r, θ, and λ denote the Earth’s spherical coordinates. The formula incorporates the n-th-order and m-th-degree Schmidt alkaline adjoint Legendre function, with N indicating the highest order, and $g_n^m$ and $h_n^m$ are the Gaussian spherical harmonic coefficients. The components $X^{(t)}$, $Y^{(t)}$, and $Z^{(t)}$ represent the northward, eastward, and vertical components of the total geomagnetic intensity in Earth coordinates, respectively. According to the 2020 IGRF model, the central geomagnetic dip in the Dasuji molybdenum deposit is 60.6958°, the magnetic declination is −6.6210°, and the normal geomagnetic field strength is 55,819.5 nT. Using these data, the geomagnetic total intensity (∆T) can be calculated.

3.2. CSAMT Survey

The transmitter generated electromagnetic signals at various frequencies (1 Hz to 8192 Hz), while the receivers measured the electrical and magnetic signals in the far field using polar and magnetic probes, respectively (Figure 6). The simplified expressions for the apparent resistivity (ρ_s) and exploration depth (H) are calculated using Equation (4):

$${\rho }_s={\displaystyle \frac{1}{5f}}{\displaystyle \frac{{\left|E_x\right|}^2}{{\left|H_y\right|}^2}}$$

(4)

$$H\approx 356\sqrt{{\displaystyle \frac{\rho }{f}}}$$

(5)

where E_x and H_y represent alkaline horizontal electromagnetic fields, and ρ and f denote resistivity and frequency, respectively. CSAMT data were collected along a north–south-trending section (500 m), aligned with the inclination of the molybdenum ore body. The transmitter current ranged from 20 A to 3 A, with the distance between the transmitter and receiver approximating 9.8 km. The length of the electric dipole transmitter was about 1500 m.

4. Geophysical Results

4.1. Aeromagnetic Results

The interpretation of magnetic anomalies involves data preprocessing, conversion, and analysis. The data processing software used in this study was the RGIS software 2010. A critical step in preprocessing is dividing sub-regions that exhibit significant discrepancies in the magnetic field. In the polarized magnetic anomaly total field (∆T), two remarkable east–west-trending negative value zones and two positive zones appear in a parallel, staggered pattern, labeled as A, A’, B, and B’, respectively. In sub-regions A and A’, the central negative magnetic zone aligns with the Dasuji molybdenum deposit. The western section corresponds to Tertiary shale, while the northern area consists of Quaternary loess. In sub-regions B and B’, the highest positive magnetism corresponds to Mesoarchean plagioclase granite, while the higher positive magnetism is associated with Mesoarchean porphyritic alkali feldspar granite (Figure 7a). On the conversion map, ∆T is decomposed into three components: the vertical Z-direction magnetic anomaly (Za (A)), the horizontal X-direction magnetic anomaly (Hax (T)), and the horizontal Y-direction magnetic anomaly (Hay (H)). Within sub-region A’, the migration direction of the three negative magnetic components indicates that the porphyry molybdenum bodies extend east–west and dip southward (Figure 7b–d). Upward continuation in the spatial domain, performed at different altitudes (50 m, 100 m, 200 m, and 300 m), reveals a southeastward migration of sub-region A’ with decreasing negative magnetic intensity (Figure 7e–h). This supports the inferred trend and inclination of the porphyry molybdenum bodies. The first vertical derivative, combined with upward continuation, highlights details at various depths. The negative magnetism in sub-region A’ is further divided into three minor anomalies (Figure 7i). Additionally, a new negative magnetic zone is identified in the southeast, becoming more prominent at greater upward continuation depths (Figure 7j–l). These findings suggest that the porphyry was emplaced along a northwest–southeast-trending fracture system, leading to the formation of the Dasuji molybdenum deposit.

4.2. CSAMT Results

Accurately predicting complex geological bodies requires integrating information from multiple geophysical datasets [26,27,28]. A two-dimensional inversion was conducted using commercial software Scs2d 3.2.exe, developed by Zonge Company (Texas, USA). The results of the smooth Cagniard resistivity and impedance phase analyses confirmed that the field survey data were accurate and reliable (Figure 8b,c). The software collected observed data and built a new model section, incorporating line annotations, survey configurations, and inversion controls. After multiple iterations, the initial inversion resistivity was obtained. The software then automatically updated the model section to refine the resistivity through further inversion. Finally, the inversion errors were approximately 2.41%, which were below the required threshold (less than 5%).

The apparent resistivity generally ranges from 100 to 1000 Ω·m. However, shallow low-resistivity (below 50 Ω·m) and high-resistivity bodies (above 4000 Ω·m) are superimposed to form a complex geoelectric structure. Lateral variation: the CSAMT results can be divided into two segments. The first segment (sites 19–16) exhibits intermediate resistivity (100–500 Ω·m) and corresponds to Archean gneiss exposed at the surface. The second segment (sites 15–0) displays intermediate to high resistivity (1000–3000 Ω·m), representative of Triassic granite porphyry. Vertical variation: the resistivity sounding curve follows an H-type curve, indicative of a three-layer electrical structure comprising high-resistivity, low-resistivity, and high-resistivity layers. The thickness of the top high-resistivity layer decreases from south to north, varying from 150 m to 10 m. Meanwhile, the second low-resistivity layer becomes progressively thicker, corresponding to the third high-resistivity layer. To verify the geoelectric structure, three drillings were conducted at different depths. These revealed that (i) the shallow low-resistivity layer corresponds to oxidized molybdenum ore found at elevations ranging from 1470 m to 1346 m, (ii) the middle low-resistivity layer corresponds to sulfide molybdenum ore located at elevations from 1345 m to 1056 m. The ore bodies align with the low-resistivity zones, forming an inverted, gently tilted, half-bell-shaped structure (Figure 8a).

5. Discussion

5.1. Why Does the Dasuji Ore-Bearing Porphyry Exhibit Negative Magnetism?

Granitoids are widely distributed in the continental crust and serve as records of early geodynamic processes. Generally, they are classified into I-, S-, or A-types based on their formation environment and material composition [29,30,31]. S-type granitoids, due to their high SiO₂ content and low ferromagnetic material content, typically exhibit lower magnetic characteristics compared to I- or A-type granitoids [32]. At the Dasuji molybdenum deposit, quartz porphyry, associated with early-stage molybdenum mineralization, is classified as an A-type granitoid, Granite porphyry, which forms the main molybdenum ore bodies, belongs to high-K calc-alkaline and peraluminous rocks, characteristic of I-type granitoids [6]. Unlike S-type granitoids, I-type granitoids generally contain more ferromagnetic substances due to their crust–mantle mixing origin. This would theoretically result in higher levels of geomagnetic total intensity values compared to A- or S-type granitoids. However, the magnetic data from the Dasuji deposit contradict this expectation. The granitoid porphyry exhibits strong negative magnetism (−100 to −300 nT), while the quartz porphyry shows weakly positive to neutral magnetic characteristics (−100 to 0 nT). This unexpected result raises an important question: why does the Dasuji ore-bearing porphyry display negative magnetism?

Several critical factors can reduce granite’s magnetism, including low oxygen fugacity, high crystallization temperatures, and hydrothermal alteration. During the magmatic mineralization stage, a low-oxygen-fugacity environment may oxidize magnetite (or pyrrhotite) into hematite or ilmenite. As is well known, the temperature at which ferromagnetic or ferrimagnetic materials transform into paramagnetic substances is called the Curie temperature. The Curie temperature of iron is approximatively 770 °C. Studies indicate that the granite porphyry under investigation is highly siliceous (up to 76.2%), with calculated zircon saturation temperatures (TZr) ranging from 762 °C to 774 °C (average 768 °C) [33,34,35]. Additionally, the quartz porphyry, classified as an A-type granitoid, also likely exceeds this critical temperature. Consequently, the granitoids associated with molybdenum mineralization have surpassed the Curie temperature and experienced a magnetic weakening effect [36]. Moreover, hydrothermal alteration can further destroy magnetic minerals. Consequently, the Dasuji ore-bearing porphyry exhibits weakly magnetic or paramagnetic properties [37,38,39].

5.2. Deep Mineral Exploration in the Dasuji Molybdenum Deposit

Most large or super-large porphyry deposits are typically identified as massive ore bodies in the second prospecting space (500–2000 m depth). Examples include the Mount Pleasant W-Mo deposit, the Qulong Cu-Mo deposit, and the Dexing Cu-W deposit [35,36,37].

Successful deep mineral predictions have been achieved at the Qulong porphyry deposit using the magnetic and CSAMT methods [40]. Upward continuation and first vertical derivative analyses of magnetic data indicate that the porphyry molybdenum bodies trend eastward and incline southward. The second low-resistivity layer detected by CSAMT correlates with oxidized molybdenum ore located at elevations between 1470 and 1346 m, while the middle layer corresponds to sulfide molybdenum ore situated from 1345 to 1056 m (Figure 9a). The southern inclination of the molybdenum ore bodies and the unclosed low-resistivity layer suggest significant potential for deep mineral exploration. Additionally, negative magnetism along the north–south-trending magnetic profile implies that the porphyry extends to a depth between sites 12 and 40. To assess the potential for deep-seated mineralization, the Inner Mongolia Nonferrous Metal Geological Exploration Bureau conducted five deep drillings in the southern region between 2015 and 2018 (Figure 9b). All drillings successfully intersected industrial-grade molybdenum ore bodies. By 2018, the estimated molybdenum resource was approximately 112 million tons, with about 149,358 tons of molybdenum metal at an average grade of 0.13% by the control block segment method (see

Table 3. Block method estimates of Mo resource in No.1 ore bodies.

Ore Type	Elevation (m)	Resource Reserve Type (code)	Control Block Segment Volume (m3)	Density (t/m3)	Ore Content (kiloton)	Mo (ton)	Average Degree (%)
Oxidized ore	1470–1346	−331	1120,623	2.57	2880	2726	0.10
		−332	762,110	2.56	1951	1616	0.08
		−333	628,516	2.56	1609	1403	0.09
		All	2511,249		6440	5745	0.09
Sulfide ore	1345–1056	(122b)	14,832,558	2.58	38,268	50,679	0.13
		−333	12,907,751	2.58	33,302	44,268	0.13
		All	41,186,434	2.58	106,261	143,613	0.14
Total	1470–1056	(122b)	14,832,558	2.58	38,268	50,679	0.13
		−331	1120,623	2.57	2880	2726	0.10
		−332	762,109	2.56	1951	1616	0.08
		−333	1353,140	2.58	34,911	45,671	0.13
Total			43,682,558	2.58	112,701	149,358	0.13

for details). To ensure reliability, the horizontal projection and block methods were applied and compared. The differences in ore and metal tonnages are reported in

Table 4. Mo resource estimates verified by the horizontal projection method.

Block Number	Block Method		Horizontal Projection Method		Estimated Difference
	Ore Content (Kt)	Mo (ton)	Ore Content (Kt)	Mo (ton)	Ore Content (Kt)	Mo (ton)
122b-7	967.20	1508.86	1022.30	1686.71	−55.10	−177.85
122b-8	1347.10	2357.55	1672.40	3093.92	−325.30	−736.37
121b-1	1694.00	2608.76	1628.90	2557.39	65.10	51.37
121b-2	2100.20	3045.32	1980.60	2911.48	119.60	133.84
121b-3	2328.90	3283.86	2295.30	3305.29	33.60	−21.43
121b-4	2645.10	3491.65	2720.30	3617.96	−75.20	−126.31
121b-5	3348.80	3817.73	3325.50	3890.79	23.30	−73.06
121b-6	1388.60	2180.17	1382.70	2212.32	5.90	−32.15
121b-7	1446.20	2097.02	1495.70	2228.59	−49.50	−131.57
121b-8	1706.70	2508.88	1702.20	2570.35	4.50	−61.47
121b-9	2029.30	2678.75	1889.00	2512.36	140.30	166.39
121b-10	1379.20	1668.84	1224.20	1469.00	155	199.84
Total	22,381.30	31,247.39	22,339.00	32,056.16	42.30	−808.77
Difference					0.19%	−2.52%

. The differences in percentage on the total ore content and Mo are 0.19% and −2.52%, respectively (see Table 3 and Table 4 for details).

6. Conclusions

(1)

New magnetic data further confirmed that the Dasuji molybdenum mineralization-related granitoids have surpassed the Curie temperature and experienced a magnetic weakening effect.

(2)

According to the CSAMT and drillings results, the molybdenum resources are estimated at about 112 million tons, with a molybdenum metal content of approximately 149,358 tons and an average grade of 0.13%.

(3)

Geophysical results identify that the porphyry molybdenum bodies tend to extend eastward and southward, respectively, playing an important role in deep molybdenum prospecting.