Fig. 3- 1 Geological Schematic Diagram of the Periphery of Baolige Silver-Gold Mine in Jilin Province
I. Occurrence characteristics of granite
(1) Early and Late Ages of Aqin Chulu Rock Body
A Qin Chuluyan is located 5 km to the northwest of Lige Silver Gold Deposit in Lin Bao, Jilin Province, and distributed in the areas of Budun Huanaote and A Qin Chulu to Junggar (Figure 3- 1). The length of NE-SW is about 26-38 km, and the width of NW-SE is 7- 14 km, which is in the shape of a wedge with narrow NE SW. The rock mass intruded into the argillaceous slate and siltstone of the Devonian Anglyinwula Formation, and was baked by the intrusion heat source of the rock mass. The argillaceous slate and siltstone of Anger Yinwula Formation often appear angular near the rock mass and produce thermal metamorphic spots. Detailed field investigation and isotopic dating work show that the Aqinchulu rock body is a bedrock with two intrusions. The early intrusive body is medium-fine grained adamellite, and the late intrusive body is fine grained biotite adamellite.
Spherical weathering (plate ⅰ-2), mainstream structure and joints developed in the early intrusive rock mass, and the occurrence of joint surface was 140 ∠ 72. Rock mass can be divided into marginal facies and transitional facies. The marginal facies is located in the periphery of the rock mass with fine-grained to medium-grained structure, and the transitional facies is located in the middle with fine-grained porphyritic structure (Geological Bureau of Inner Mongolia Autonomous Region, 1978b). Due to magmatism, the rock mass produced strong autometamorphism and formed greisenization, which gradually weakened from both sides of the rock mass to the inside. Veins and traps in the rock mass are well developed, and the derived dikes are mainly fine-grained adamellite veins, which generally run through the joints in the northeast direction, and a few are in the northwest direction and SN- direction. In addition, chronological veins, diorite, diabase and syenite veins are also found in the rock mass, most of which are NW-trending, and a few are NE-trending and nearly EW-trending.
In contrast, the grain size of the late intrusive rock mass is fine, and it intrudes into the early rock mass along the joint, and has obvious contact boundary with the surrounding rock, or captures the early rock mass, and has a gradual contact relationship with the early rock mass (Plate I-3).
(2) Baolige Rock Mass in Jilin Province
Jilin Baolige rock strain is located in the east of Jilin Baolige silver-gold deposit (Figure 3- 1). Deep drilling and tunnel exploration show that the strain of Baolige rock mass in Jilin Province extends westward to the deep part of Baolige mining area in Jilin Province. The exposed area of rock mass on the surface is about 1 km2, which is distributed in the east-west direction. The landform is dome landform, the contact zone between rock mass and surrounding rock is not obvious, and the surrounding rock is covered by Quaternary remnants. The main lithology is fine-grained porphyritic adamellite. Limonite, pyrite and silver-gold mineralization are developed in the rock mass, which are often distributed in a plane and disseminated manner, and the mineralization in the fracture development area is strong.
Second, the petrological characteristics
(1) Early and Late Ages of Aqin Chulu Rock Body
The early intrusive medium-fine adamellite is grayish white, fleshy red, and grayish yellow after weathering. Adamellite texture. The main minerals are plagioclase (30% ~ 35%), potash feldspar (35% ~ 40%) and syenite (20% ~ 25%), and a small amount of biotite (5% ~ 7%), zircon (< 1%) and apatite (1%). Plagioclase is mostly self-shaped-semi-self-shaped plate. Potash feldspar is mostly shaped plate, some of which are authigenic plate, with undeveloped micro-stripe structure and twin spindle lattice. A part of the timing is granular, most of them are shaped, and a part of the timing forms a schlieren structure with potash feldspar. The biotite is irregularly flaky and evenly distributed. The particle size of minerals is generally 0.5~2 mm, and a small amount of syenite and plagioclase can reach 2 ~ 5 mm, even15 mm.
The late intrusive body is fine-grained adamellite, grayish white and fleshy red. Adamellite texture. The main minerals are plagioclase (30% ~ 35%), potash feldspar (≥40%) and syenite (20% ~ 25%), and a small amount of biotite (5% ~ 7%), zircon (< 1%) and apatite (1%). Plagioclase is mostly self-shaped-semi-self-shaped plate. Potassium feldspar is partly authigenic-semi-authigenic plate with Cartesian twins, and partly abnormal plate. Most of them are shaped and granular. The biotite is uniformly distributed in sheets. The mineral particle size is small, generally 0.5 ~1mm.
(2) Baolige Rock Mass in Jilin Province
The representative rock is fine-grained porphyritic adamellite with porphyritic texture. The main minerals are plagioclase (35% ~ 40%), potash feldspar (30% ~ 35%) and syenite (20% ~ 25%), and a small amount of biotite (5% ~ 7%), zircon (< 1%) and apatite (1%). Porphyry crystals are mainly plagioclase, which is self-plate-shaped, and the particle size is generally between 5 ~ 5 ~ 8 mm. In the matrix, plagioclase is mostly semi-self-shaped-shaped plate, and potassium feldspar is also semi-self-shaped-shaped plate. It is granular in time, and biotite is mostly flaky. The mineral particle size is 0.5 ~ 2mm (Plate I-5).
There are diorite black inclusions in the rocks. Plagioclase is often replaced by sericite and clay minerals, while biotite is replaced by chlorite.
Third, the characteristics of constant elements
See Table 3- 1 for the contents of major element oxides in Aqin Chulu rock mass and Baolige rock mass in Jilin Province. As can be seen from the table, there are many similarities among the three rock masses, as follows: ① Silicon-rich: SiO2 _ 2 content is 68.59% ~ 74.42%, and the differentiation index di is 55.94 ~ 62.94. ② rich in alkali, K2O>Na2O, with K2O content of 4.28% ~ 5.3% and Na2O content of 3.32% ~ 3.67%; K2O+Na2O is 7.68% ~ 8.75%; The ratio of K2O/Na2O is 1.20 ~ 1.54, which is similar to the K-rich calc-alkaline granite classified by Barbarin( 1999). On the SiO _ 2-K2O diagram (Figure 3-2), the sample belongs to the "high potassium calcium alkaline series" area. ③ Al is weakly supersaturated, and Al2O3 is13.63% ~14.21%; The values of A/CNK are 1.04 ~ 1. 15, all of which are greater than 1, but most of them are between 1 ~ 1, which is different from the typical peraluminum s in A/NK-A/CNK diagram. ④ Corundum molecules appear in all CIPW standard minerals, all of which are larger than 1%, similar to typical S-type granite (Miller et al.,1980; Chapel et al., 200 1).⑤ The content of iron, magnesium, calcium, titanium and phosphorus is lower, but higher than that of peraluminous granite in Mai Sha, Inner Mongolia (Hu Peng et al., 2006). The molecular number of Mg # is 35.57 ~ 43.65. Rietmann assemblage index σ is 2. 13 ~ 2.58, belonging to calc-alkaline rock series.
Figure 3-2 wSiO2%-K2O% Map of Baolige and Aqinchulu Rock Bodies in Jilin Province
Figure 3-3 A/NK-A/CNK Diagram of Baolige and Aqin Chulu Rock Bodies in Jilin Province
By comparing the major elements of Baolige, Jilin and Chulu, A Qin, we can find that there are some subtle differences among the three rock masses: with the intrusion sequence of Baolige adamellite in Jilin-Chulu early adamellite in A Qin-Chulu late adamellite in A Qin, the elements such as iron, magnesium, calcium, manganese, titanium and phosphorus gradually decrease, while the potassium and differentiation index gradually increase. This law shows that the degree of crystallization differentiation of adamellite increases with time, and elements such as iron, magnesium, calcium, manganese, titanium and phosphorus are gradually depleted in the later rock mass, while potassium is continuously enriched.
Fourthly, the characteristics of rare earth elements
See Table 3- 1 for the analysis results of rare earth elements in the early and late rocks of Baolige and Aqin Chulu in Jilin Province, and the analysis results of rare earth elements are as follows.
(1) Jilin Baolige adamellite
The total amount of rare earth elements in the five samples is (192.27 ~ 205.64 )×10-6, and the average value is199.13×10-6. LREE/HREE is 5.75 ~ 6.36, with an average of 6. 1.3, and LREE is slightly higher than HREE. (La/Yb)N ranged from 5.37 to 6.37, with an average of 5.94; δEu is 0.39 ~ 0.42, with an average value of 0.40, showing a strong negative anomaly of Eu. Ce has weak positive abnormality. On the spider web diagram of rare earth elements (Figure 3-4), the rare earth distribution curves of the five samples are very similar, and the distribution curves are generally inclined to the right, among which the heavy rare earth Ho-Lu is flat.
Table 3- 1 Analysis results of major elements (wB/%), rare earth elements and trace elements (wB/ 10-6) in Baolige, Jilin and Chulu, A Qin.
sequential
(2) Early adamellite in Aqinchulu.
The total amount of rare earth elements in the three samples is (140.53 ~151.40) ×10-6, and the average value is145.39×10-6. LREE/HREE is 9.75 ~ 9.95, with an average of 9.85. LREE is slightly richer than HREE. (La/Yb)N varies from11.25 ~11.88, with an average of11.57; Δ Eu is 0.52 ~ 0.54, with an average value of 0.53, showing moderate negative EU abnormality; Ce anomaly is not obvious. On the spider web diagram of rare earth elements (Figure 3-4), the distribution curves of rare earth elements of the three samples are generally right oblique, and the distribution curves of heavy rare earth Ho-Lu are flat.
(3) Late Achin Chulu adamellite
The total amount of rare earth elements in the three samples is (120.71~147.82) ×10-6, and the average value is135.22×10-6. The ratio of LREE/HREE is11.34 ~13.81,and the average value is 12.33. LREE is weak and rich compared with HREE. (La/Yb)N ranges from 14. 16 to 18.68, with an average of16.05438+0; Δ Eu is 0.54 ~ 0.57, with an average value of 0.55, showing moderate negative EU abnormality; Ce has a weak negative anomaly. On the spider web diagram of rare earth elements (Figure 3-4), the distribution curves of rare earth elements of the three samples are generally right oblique, and the distribution curves of heavy rare earth Ho-Lu are flat.
To sum up, the total amount of rare earths in Baolige, Jilin and Chuluyan, A Qin ranges from (120.71~ 205.64) ×10-6. With the intrusion sequence of Baolige adamellite in Jilin-early adamellite in Chuzhou, A Qin-late adamellite in Chuzhou, A Qin, the total amount of rare earths gradually decreased, and LRs. Therefore, these three rocks should have the same magma source area, and it is speculated that there are plagioclase and garnet in the same source area.
Figure 3-4 Standardized curve of rare earth chondrites in Baolige and Aqinchulu rocks in Jilin Province.
The characteristics of trace elements in verb (abbreviation of verb)
(A) the content of trace elements
See Table 3- 1 for trace element analysis results of early and late adamellite in Baolige and Aqinchulu, Jilin. The analysis results show that the average K/Rb of early and late adamellites in Baolige, Jilin and Aqinchulu are 158.54, 148.08 and 169.438+0 respectively. Although the contents of trace elements in the three rock samples are different, their curve shapes in the original mantle standardization map (Figure 3-5) are basically the same, indicating that they have the same (or similar) material sources. As can be seen from the figure, this kind of rock is rich in MagmaElemental (Rb, Ba, Th, U, K). On the contrary, elements with high field strength (Ta, Nb, Ti, P) show loss characteristics. In addition, the contents of ore-forming elements such as lead, zinc, gold and silver are higher than the Clark value of the crust, while copper (generally less than 10× 10-6) is much lower than the Clark value (100× 10-6, Clarke et al., 65438+). The comparative analysis shows that the contents of Cu, Pb, Zn, Au, Ag and Mo in Baolige rock mass in Jilin Province are all higher than that in Aqinchulu rock mass, especially the contents of Au and Ag are more than two orders of magnitude higher than Clark value. However, the contents of ore-forming elements in Aqinchulu rock body are almost the same in two periods, and the contents of Au and Ag are lower than Clark value. The above phenomenon shows that the ore-forming materials of Baolige silver-gold deposit in Jilin Province may mainly come from Baolige rock mass in Jilin Province.
Fig. 3-5 Original Mantle Standardization Curve of Trace Elements in Baolige and Aqinchulu Rock Bodies in Jilin Province
(2) Discrimination of tectonic environment of trace elements
The theory of plate tectonics lays a foundation for identifying various tectonic environments. With the continuous updating of various testing instruments, the progress of analysis methods and the continuous accumulation of data, there are many methods to distinguish the tectonic environment of granite-like source areas: the principal element index discrimination method proposed by Maniar et al. (1989); The discriminant diagram of R 1-R2 factor proposed by Bechelor et al. (1985); The Rb-Hf-Ta triangle diagram proposed by Harris et al. (1986) and the trace element discrimination diagram proposed by Pearce et al. (1984). Among many methods to distinguish the source environment of granitoids, Pearce et al. (1984) is the most widely used one. Pearce et al. (1984) classified all intrusive rocks with a seasonal content of more than 5% as granitoids. Firstly, the geochemical characteristics of granite with known tectonic background are systematically studied, and it is considered that elements Y, Yb, Rb, Ba, K, Nb, Ta, Ce, Sm, Zr and Hf can effectively distinguish different tectonic environments in which granite was formed.
On Pearce et al.' s (1984) discriminant diagram of tectonic environment, no matter the discriminant diagrams of Nb× 10-6-Y× 10-6 and Ta× 10-6-Yb× 10-6,
Figure 3-6 Discrimination of early and late adamellite Nb× 10-6-Y× 10-6 (Figure A) and Ta× 10-6-Yb× 10-6 (Figure B)
Isotopic composition of intransitive verbs
(1) lead isotope
Because the content of uranium and thorium in potash feldspar is very low, the radioactive lead accumulated since the formation of the rock can be ignored. Usually, the lead isotopic composition of potash feldspar in granite represents the initial lead isotope of rock mass (Zartman et al.,1981; David Hong et al., 2002), therefore, this study selected potash feldspar in granite as the determination object. The analysis and calculation results of lead isotopic composition of seven samples of Jilin Baolige and Aqinchulu adamellite are listed in Table 3-2. The results of lead isotope analysis listed in Table 3-2 show that the lead isotopic composition of adamellite in different periods in Baolige, Jilin and Chulu, A Qin is obviously similar. The whole rock of potash feldspar and adamellite is rich in radioactive lead, and the values of 206 Pb/204 Pb, 207 Pb/204 Pb and 208 Pb/204 Pb vary in a narrow range. The ratio of 206 Pb/204 Pb of seven samples ranged from 17.987 ~ 18.470, with an average of 18.207. The value of 207 Pb/204 Pb is 15.467 ~ 15.520, and the average value is15.498; The value of 208 Pb/204 Pb is 37.762 ~ 38. 1 12, and the average value is 37.9 1 1. The lead isotopic composition of adamellite is close to the mantle value of 206pb/204pb =18.10, 207 Pb/204 Pb= 15.42 and 208 Pb/204 Pb=37.70 (Doe, 1979. The parameters such as μ, ω and Th/U calculated by single-stage lead evolution model have little change in different samples. The μ value is between 9.25 and 9.32, which is lower than the continental crustal evolution line with μ value of 9.74. Th/U value ranges from 3.55 to 3.65, which is close to chondrite (3.58) and close to the earth (Wedepohl,1974; Female deer and so on. , 1979; Wei Juying et al., 1996), indicating that the consistency of the source areas of the three rock masses is related to mantle-derived magmatism.
Fig. 3-7 Early and late adamellite Rb×10-6-(y+nb )×10-6 (Figure A) and Rb×10-6-(Yb+Ta )×/kloc-0.
Table 3-2 Lead Isotopic Composition of Baolige and Aqinchulu adamellites in Jilin Province
Note: Analysis results of Analysis and Testing Research Center of Beijing Institute of Geology, Nuclear Industry.
Shen Weizhou (1997) studied the lead isotopic composition of feldspar in granite bodies in South China. The results show that the 206Pb/204Pb values of crust-derived granite and crust-mantle mixed granite are similar, but the 207Pb/204Pb values are different. The 207Pb/204Pb value of crust-derived granite feldspar is usually greater than 15.600, and the 207Pb/204Pb value of crust-mantle mixed granite feldspar is usually less than 15.600. As can be seen from Table 3-2, the 207Pb/204Pb values of early and late feldspar in Baolige and Aqinchulu of Jilin Province are lower than 15.600, indicating that it may be related to the addition of mantle or young crustal materials. On the 207Pb/204Pb-206Pb/204Pb and 208pb/204pb maps (Figure 3-8a, B), the distribution pattern shows the evolution trend from mantle lead to orogenic lead. In Figure 3-8c, the lead isotope composition is located on the right side of the earth's isochron, in the lead distribution area between the lower continental crust and EM ⅱ. The above-mentioned lead isotope structure model diagram reveals that the three rock masses have the characteristics of mixing mantle-derived components and lower crust components.
Fig. 3-8 lead isotope structure model of early and late adamellite in Baolige and Aqinchulu, Jilin Province.
(ii) Rubidium-strontium isotope
The contents of Rb and Sr in seven samples of early and late adamellite from Baolige and Aqinchulu in Jilin Province are not much different (Table 3-3). The contents of rubidium and strontium vary between (164 ~ 229) × 10-6 and (99 ~ 158). The 87Rb/86Sr ratio of seven samples varied from 3.00 1 ~ 6.45438+066, with an average of 4.5626. The ratio of 87Sr/86Sr is relatively large, ranging from 0.716302 to 0.726028, with an average value of 0.72 1329. The initial ratio of (87Sr/86Sr)i ranges from 0.695 14 to 0.70456, with an average of 0.705438+078. White et al. (1983) think that the initial ratio of (87Sr/86Sr)i of S-type granite is greater than 0.707, while that of I-type granite is less than 0.707. The above results show that the initial ratios of (87Sr/86Sr)i of the early and late rocks in Baolige and Aqinchulu, Jilin Province are less than 0.707, indicating that these three rocks have mantle-derived characteristics.
Table 3-3 Isotopic Analysis and Calculation Results of Rb, Sr and Sm, Nd in Jilin Baolige and Aqinchulu adamellites
(3) samarium neodymium isotope
See Table 3-3 for the results of Sm-Nd isotopic analysis of seven samples from early and late three adamellite granites in Baolige and Aqinchulu, Jilin. As can be seen from the table, the ratio of 147Sm/ 144Nd changes from 0.0777 to 0. 10 19, with an average value of 0.08827, which is smaller than the initial value of chondrite homogeneous library (0. 1967).
1. Model age
In the single-stage model, the TDM values of the three rock masses are between 664 and 775 Ma, all exceeding their formation ages (286-365,438+04 Ma). Jiangfeng Chen et al. (1999) think that the two-stage model can effectively correct the error of TDM value caused by crystallization differentiation of granite slurry. However, the two-stage model age calculation results of three granites in this area show that the T2DM value is 723 ~ 982Ma, which is larger than the TDM value and quite different from the actual age of granites. Therefore, the two-stage model does not conform to the evolution characteristics of granite in Baolige area of Jilin Province. It is generally believed that the model age of granitic rocks can be used to estimate the age of their source areas. For mantle-derived granite, the model age gives the time when basaltic rocks evolved into granite by mantle fractionation, which is close to the crystallization age of granite (Hugh, 1993). For granite, the model age represents the time when the sample separated from the mantle, on the premise that the sample originally originated from the mantle. However, for granite with mixed source of crust and mantle, the calculated model age often deviates greatly (Goldstein et al., 1984). The above calculation results show that the age of single-stage model and two-stage model are quite different from the actual age, indicating that the material sources of the three granites in this area may be related to the mixed pollution of crust and mantle. On the other hand, the TDM values of three rock masses in Baolige area of Jilin Province vary in a small range of 664~775 Ma, and the TDM values of igneous rocks in orogenic belt (concentrated in 800~600 Ma) (David Hong et al., 2000; Ji Shaoan et al., 2002), indicating that there is a close genetic relationship between them.
2.εNd(t) value
The value of εNd(t) reflects the relative deviation between the initial value of 143Nd/ 144Nd and the original unmelted mantle during rock crystallization. If εNd(t)=0, it means that the rock comes from mantle reservoir with Sm/Nd ratio of chondrite. The positive εNd(t) value indicates that magma comes from the source region with higher Sm/Nd than CHUR, such as the depleted mantle source region. A negative value of εNd(t) indicates that the Sm/Nd of magma source region is lower than that of CHUR, such as rich mantle source region or crustal source region (Hugh, 1993). As can be seen from Table 3-3, the εNd(t) values of three rock masses in Baolige area of Jilin Province are all greater than 0, ranging from 0.8 to 4.3. The value of εNd(t) indicates that three rock bodies in Baolige area of Jilin Province may come from depleted mantle endmembers. On the plot of εNd(t) value and model age (Figure 3-9a), all sampling points fall within the range of Meng Xing orogenic belt delineated by Hong Dawei et al. (2000). On the graph of the relationship between εNd(t) value and intrusion age (Figure 3-9b), most of the projection points fall in or near the granite in the orogenic belt circled by David Hong et al. (2000).
Fig. 3-9 Relationship between εNd (t) value of early and late adamellite in Baolige and Aqinchulu, Jilin Province and intrusion age (the original figure is based on David Hong et al., 2000).
Seven, SHRIMP zircon U-Pb age
(1) zircon characteristics
Most zircon crystals in Baolige adamellite in Jilin Province are complete in crystal form, clear in crystal face, transparent and clean, mostly in short column or long column shape, with a grain size of 100 ~ 200μ m, a general aspect ratio of 2 ~ 3, and a few less than 2. More than 65,438+000 zircons were photographed by cathodoluminescence. Some zircons contain ancient zircon cores surrounded by young accretion layers, and the photos show obvious rhythm zones of magmatic oscillation (Figure 3-65,438+00). Zircon crystals of early adamellite in Aqinchulu are complete, crystal faces are clear, and the crystals are transparent and clean, mostly in short or long columns, but mainly in long columns. The particle size is generally 100 ~ 300μ m, the aspect ratio is generally 3 ~ 5, and the individual aspect ratio is 8. More than 100 zircons were photographed by cathodoluminescence method, and it was found that some zircons had ancient zircon cores with young accretion layers around them. The photo shows obvious magmatic oscillation rhythm zone (Figure 3- 1 1).
Zircon crystals of the late adamellite in Aqinchulu are in good shape, transparent and clean, mostly short columns or long columns. The particle size is generally 50 ~ 150μ m, and the aspect ratio is generally 1 ~ 3. Zircon cathodoluminescence photography shows that there is no old zircon core, and the photo shows the obvious rhythm zone of magma oscillation (Figure 3- 12).
Fig. 3- 10 Cathodoluminescence Image of Zircon in Baolige adamellite in Jilin Province
(ii) Test results
The test results of 10 zircon in Baolige adamellite in Jilin Province are listed in Table 3-4. The content of 206Pbc in 10 measuring points ranged from 2.81%to12.79%, most of which were less than 10%. The contents of uranium and thorium are (131~ 680 )×10-6 and (44 ~ 4 10) × 10-6, respectively. Th/U ratio is 0.30 ~ 0.73, with an average value of 0.43, slightly lower than 0.5 (Vavra et al., 1996,1999; Liu Dunyi, 2003). The 206Pb/238U ages of nine zircons were corrected with 204Pb, ranging from 272.6 8.3ma to 34612ma+02ma with an average of 314 8.8ma.. The weighted average age of 206Pb/238U is 314 8.8ma, and MSDW= 1.7 (fig. 3- 13a) on the age charts of eight measuring points from 207pb/235u to 206pb/238u. The older age of 206 Pb/238 u (565,438+06 20ma) was obtained from the zircon center of 65,438+0 (measuring point 8.0), indicating the age of inherited zircon from the source rock. See Table 3-4 for the test results of early adamellite 12 zircon in Aqinchulu. The content of 206Pbc in 12 measuring point ranges from 0.35% to 7.29%, and is concentrated between 2% and 6%. The contents of uranium and thorium are (235 ~ 1064) × 10-6 and (23 ~ 65 1) × 10-6, respectively. Th/U ratio is 0.06 ~ 0.89, with an average value of 0.45, which is slightly lower than that of magmatic zircon (Vavra et al., 1996,1999; Liu Dunyi, 2003). The age of 1 1 zircon of 206Pb/238U is corrected by 204Pb, and the range is 286.01ma ~ 322.17.4ma, with an average of 299.5ma ... at 207pb/235. The weighted average age of 206Pb/238U is 299±5ma, and MSDW= 1.4 (Figure 3- 13b). The older age of 206Pb/238U (807 17 Ma) was obtained at the center of 1 zircon (measuring point 8.0), indicating the age of inherited zircon from source rocks.
Table 3-4 lists the five SHRIMP test results of five zircons in the late Ahengqiulu adamellite. The content of 206 Pbc in five measuring points ranged from 3.85% to 65438 00.04%. The contents of uranium and thorium are (79 ~ 444 )×10-6 and (51~ 223 )×10-6, respectively. Th/U ratio is 0.22 ~ 0.66, with an average value of 0.54, which is higher than 0.5 (Vavra et al., 1996,1999; Liu Dunyi, 2003). The 206 Pb/238 U ages of four zircons are corrected by 204 Pb, ranging from 276.5 9.8ma to 29612ma+02ma, with an average of 284.3±9.7Ma. On the age chart of 207 Pb/235 U-206 Pb/238 U, the data points are distributed in the harmony line and its vicinity. The weighted average age of 206 Pb/238 U is 284.3±9.7ma, and MSDW=0.77 (Figure 3- 13 c). The older age of 206 Pb/238 U (429 15 Ma) is obtained from the edge of 1 zircon (measuring point 4.0), which may be related to the loss of the female U in it.
Fig. 3- Zircon Cathodoluminescence Image of Early Achchulu adamellite +0 1
Fig. 3- 12 Cathodoluminescence Image of Zircon in Late Achechulu adamellite
Table 3-4 Early and Late Zircon SHRIMP U-Pb Age Analysis Results of Baolige Rock Mass in Jilin and Chulu Rock Mass in A Qin
Fig. 3- 13 zircon U-Pb harmony map of early and late rocks in baolige and aqinchulu, Jilin province