Metallogenic sub-series of iron, copper, molybdenum, lead, zinc, antimony and pyrite deposits related to Yanshanian syntectic intermediate-acid rocks (5a)

The deposits belonging to this sub-series mainly include: Zhuli iron-zinc-molybdenum deposit (medium-sized) around the Shanxi granodiorite body in Shaoxing-Zhuji (typical deposit 21); Loujiawu iron mine, Ganxiwu iron mine, Huangyoutang polymetallic mine, Siwuling lead-zinc mine, etc. Xianlinbu Fe-Mo-Cu deposit (medium-sized) (typical deposit 22) occurring in the contact zone of Xianlinbu granodiorite in Yuhang; Shangtaimen lead-zinc mine (typical deposit 23), Qianjiacun iron mine and Langjinwu iron mine around Qianjiacun granodiorite in Fuyang; Xikou pyrite polymetallic deposit (large and medium-sized) and Jintiansi silver-cobalt deposit around Mu Chen quartz monzonite in Longyou; Port boron-bearing iron ore of Wushanguan rock mass in Anji, Meng Jie polymetallic mine of Chengjiayaojia rock mass in Chun 'an, Sanbaotai antimony mine (typical deposit 24).

(A) the main ore-controlling conditions

1. All rocks related to mineralization belong to syntectic magmatic rocks.

This kind of rock mass belongs to the first-stage intrusive body in the early Yanshanian period, and it is in the form of small rocks or branches, with an area of 50 km2, SiO2 of 62% ~ 68%, alkali value (K2O+Na2O) of 6.11%~ 8.34%, and Na2O >: K2O, Na2O in general.

According to Shao Shousheng et al. (1990), Shao Shousheng et al. divided the tin ore-forming areas in Zhejiang Province, 1990.

Through the discrimination of 244 rock masses in the whole province, it is considered that Na2O/K2O >: 0.8, C/ACF is 0.30, ankc >: 1, Al'< 0, and the composition of rock-forming minerals, accessory minerals, trace elements and 87Sr/86Sr values, etc. The genetic types of magmatic rocks can be divided into syntectic granite (type ⅰ) and reformed granite (remelting type and S type).

The main ore-bearing rock bodies listed in Table 3-5- 1 belong to the same lava bodies, which were mainly formed in the first stage of the early Yanshan period. The age value is 197 ~ 136 Ma, and some of them belong to the late Yanshanian rock mass (Mu Chen), and the age value is 1 12Ma. Some age values measured in early work are measured by K-Ar volume method, which is too large (such as Shanxi).

Generally, the rock mass intruded along the fold axis in the NE-trending Indosinian period, mainly at the dipping end of the anticline or the section where the fold bifurcates or large transverse structures are staggered.

According to the regional survey data of1:50,000, ore-bearing synlavas are often multi-stage pulsating intrusions, such as the first-stage syntectic granodiorite in Shanxi-Guangshan rock mass, and the second-stage remelted granite in Guangshan area, invading the northwest side of the synlavas (Figure 3-5- 1). Mu Chen quartz monzonite body is characterized by pulsating intrusion of magma, forming units with different rock structures, and then syenite penetrates along the edge in the form of marginal branches. Other ore-bearing rocks are small in area and lack such information.

Table 3-5- 1 Characteristics of Yanshanian syntectic intermediate-acid rocks in Zhejiang Province

sequential

Fig. 3-5- 1 Shanxi-Guangshan rock mass geological schematic diagram (with horizontal zoning of ore body)

(According to the Fourth Geological Brigade, slightly modified)

1- four yuan; 2- Ordovician; 3- Upper Cambrian; 4- Middle Cambrian; 5- Lower Cambrian; 6-Upper Sinian; 7- Lower Sinian; 8— Fine-grained granite; 9- medium grained granite; 10-granodiorite; 1 1- failure; 12 —— the axis of the inverted anticline; 13- ore body location and mineral types; 14-Isotopic Age Sample (Ma)

2. The horizon where the deposit occurs

Subseries are mainly skarn deposits and hydrothermal metasomatic deposits, which occur in carbonate rocks. In Qiantangtai fold belt, it is mainly produced in Sinian-Paleozoic. Relevant horizons mainly include Doushantuo Formation and Dengying Formation of Upper Sinian, Dachenling Formation of Lower Cambrian, Yangliugang Formation and Huayansi Formation of Middle and Upper Ordovician, Wenchang Formation of Upper Ordovician, Wujiangtao of Carboniferous-Permian, etc. Study on metallogenic prediction report and method of metallogenic series of skarn hydrothermal deposits in western Zhejiang, 1989.

. Mineralization related to rock mass in southeastern Zhejiang occurs in metamorphic rocks or volcanic rocks.

3. The control of structure on mineralization

The control of structure on mineralization can be discussed from several levels, such as ore field, deposit and ore body.

Mineralization around the rock mass (and its concealed extension) constitutes the ore field. A single ore field is generally distributed along the fold axis or diagonally across the fold axis. The distribution of several ore fields is controlled by regional faults and the extension of gravity gradient zone. Such as Julie, Qianjiacun, Xianlinbu, Wushanguan and other places, are controlled by the turning point of NW-trending structure and gravity gradient.

The position of the deposit in the ore field is mainly in the tilting position of the fold hinge, the separation, sliding and dislocation between lithologic layers, the twists and turns, abrupt changes, bifurcation and surrounding positions of the contact zone of rock mass (Figure 3-5-2).

The enrichment of ore bodies depends on favorable mineralization horizons, with strong deformation, dislocation and loss superimposed. For example, the horizon error between Dengying Formation and Doushantuo Formation in Lizhuxi Mine is a good condition for bedding mineralization. However, most of the strata in the southeast wing have been lost, and the Ordovician contacted with the Tang Zhi Formation, resulting in extremely strong structural damage and transverse fracture superposition, forming thick iron ore bodies (Figure 3-5-3).

Figure 3-5-2 Julie-Huajie Road Section

(According to "Report on 1:50000 Julie Map Sheet", slightly revised)

1-shale of Changwu Formation; 2- Yinzhubu Formation shale; 3— Limestone of Yangliugang Formation; 4-Tanghe Formation siliceous shale; 5— Limestone of Dachenling Formation; 6— Dolomite and silty mudstone of Xifeng Formation; Sandstone and tuff of 7- Tang Zhi Formation; 8- granodiorite; 9- Fault; 10- orebody

Figure 3-5-3 Geological Plan of East Ore Section of Shaoxing Julie Iron Mine

(According to the summary of regional minerals in Zhejiang Province, 1988)

1-tuff; 2— Silty mudstone; 3- dolomite; 4- limestone; 5- shale; 6- siliceous rocks; 7- quartz porphyry; 8- iron ore body; 9- Fault; 10- geological boundary; 1 1- formation occurrence; 12- exploration route and number; 13- geological profile and number

Mu Chen rock mass is controlled by gravity gradient of Neijiang Shao fault in the area, and its position is controlled by the ductile shear zone under the temple. Zheng Guisong, Metallogenic Prediction Report of Xikou Polymetallic Pyrite Ore-forming Area in Longyou County, Zhejiang Province, 1993.

. Niujiaowan, Xikou and Lingshan deposits are all related to the physical and chemical zones of shear slices and the fault system formed by inherited slip and torsion (Figure 3-5-4).

Figure 3-5-4 Structural Schematic Diagram of Xikou Ore Field

(According to Zheng Guisong 1993, slightly modified)

(2) Mineralization and alteration characteristics

1) The contact zone in the rock mass is self-metamorphic, plagioclase increases, diopside and garnet appear, rock acidity decreases, and calcium and magnesium increase.

2) Contact zone of surrounding rock. The positive contact zone forms cystic and lenticular skarns, which are mineralized in the superimposed hydrothermal stage, and the mineralization and alteration zoning is not obvious, such as Xianlinbu. Or form layered skarns and ore bodies along the horizon, such as Julie and Shangtaimen. The mineralization of layered skarn is generally banded, and garnet skarn, iron, copper and molybdenum mineralization are mainly adjacent to the rock mass. Outward, diopside skarn, polymetallic and lead-zinc mineralization are dominant. When far away from the rock mass, lead-zinc ore and antimony ore are produced separately.

3) The ore-bearing skarns are all superimposed with water-bearing skarn minerals such as epidote and actinolite and hydrothermal alteration minerals such as chlorite, quartz and sericite.

4) The contact metamorphism between sandy argillaceous rocks and siliceous rocks forms hornfels, such as coesite hornfels, diopside hornfels, cordierite hornfels and biotite hornfels. This is related to the composition and thermal metamorphism of the original rock.

(3) Some information about the genesis of the deposit.

1) According to 17 pyrite samples in Lingshan mining area (all containing more than 40% sulfur), the average cobalt content is 26.32× 10-6 (the range is 2.5×10-6 ~150×/kloc.

2) Sulfur isotopes of 30 pyrite samples from Hedong, Niujiaowan, Lingshan, Daniuwu and Dongshan in Xikou area were determined. The δ34S value was 3.48‰, the maximum value was 5.46‰, the average value was 4.40‰, and the coefficient of variation was11.5%. δ34S are all positive values, with narrow distribution range, obvious tower effect and little numerical change in different surrounding rocks, indicating that sulfur isotopes are close to meteorite sulfur. Sulfur isotope differentiation is poor, which is the deep source sulfur brought by magmatic hydrothermal solution.

3) There are/kloc-0 rare earth samples in Lingshan, Niujiaowan, Hedong and Daniuwu, and their characteristic values are shown in Table 3-5-2. Comparatively speaking, the distribution characteristics of rare earth elements in each deposit are similar to those in host rocks. The curve of pyrite in Niujiaowan is similar to syenite, that of pyrite in Hedong is similar to biotite plagioclase gneiss, and that of Lingshan is similar to plagioclase amphibole, indicating that the ore-forming fluid exchanged materials with the surrounding rock during migration and absorbed some materials from the surrounding rock (Figure 3-5-5).

Figure 3-5-5 Comparison of Rare Earth Characteristics of Ores and Rocks in Xikou Area

(According to Zheng Guisong 1993)

Table 3-5-2 Characteristics of Rare Earth Elements in Xikou Deposit

According to the temperature measurement results of mineral inclusions in the above deposits, the temperature is mainly moderate and high, and some of them are high. There are 1 1 sample in Lingshan. The explosion temperatures of four samples are 250 ~ 300℃, four samples are 320 ~ 367℃, and three samples are 4 10 ~ 433℃. The initial temperature of Hedong is 250℃ and 365438 04℃ respectively. Niujiaowan has two samples at 264 ~ 295℃ and 365 ~ 438 05℃, and Daniuwu has two samples at 288 ~ 293℃. The upper limit temperature of each sediment is between 380℃ and 420℃, and the highest is 530℃.

4) According to the data of Shangtaimen Pb-Zn deposit, the main mineralization component of the deposit is about 300℃. Sulfur isotopic composition, δ34S is +5.02 ‰ ~+5.93 ‰, and the value is relatively concentrated. The sulfur source comes from magmatism (Table 3-5-3 and Table 3-5-4).

Table 3-5-3 Sulfur Isotope Determination of Shangtaimen Fe-Pb-Zn Deposit

Table 3-5-4 Temperature Measurement Value of Shangtaimen Iron-Lead-Zinc Mine Blasting Method

(4) Geophysical and geochemical field characteristics of ore fields and deposits.

Ore-bearing granodiorite has weak-medium magnetism, which can cause hundreds to thousands of nT anomalies. Skarns containing magnetite and pyrrhotite have linear and short-axis positive and negative magnetic anomalies because of their different shapes and occurrences, and their occurrences and scale factors can be calculated accordingly. Generally, if there are carbonaceous siliceous rocks, pyrrhotite amphibole will be formed, which will cause strong abnormal interference.

The density of rock mass is slightly less than that of Paleozoic strata, and the gravity field is weakly negative anomaly. Combined with gravity and magnetism, the occurrence and concealed extension direction of rock mass can be inferred (Figure 3-5-6).

Figure 3-5-6 Vertical second derivative diagram of gravity field in Shanxi-Guangshan rock mass area of Zhuji (R=8km)

(According to Zhejiang Geophysical Exploration Brigade 1987)

Due to the mineralization composition of the deposit, there are scattered flows around different rock masses and secondary halo anomalies of copper, molybdenum, zinc, lead and silver.

(v) Metallogenic model

See the model diagram of iron, copper, molybdenum, lead, zinc and antimony metallogenic sub-series (5a) related to intermediate-acid rocks in the early Yanshan period (Figure 3-5-7).

Figure 3-5-7 Metallogenic Models of Two Magmatic Genetic Types in Qiantangtai Fold Belt in Early Yanshan Period

(1) Julie iron mine; ② Xianlinbu Fe-Mo-Cu deposit; ③ Shangtaimen Fe-Pb-Zn mine; ④ Huangyoutang copper-lead-zinc mine; ⑤ Siwuling lead-zinc mine; ⑥ Houling Copper Mine (Yanshan superimposed transformation); A thousand acres of tungsten beryllium ore; Xiaseling tungsten-copper mine; Tongshan iron-tin mine; Huangchuanyuan copper-lead-zinc mine; Shuangxikou tin-bearing sulfide ore; Daxibian lead-zinc mine; Tin-bearing fluorite skarn in front of the rock; Xinqiao fluorite mine; Liu Zhu antimony mine