Table 2-2 Comparison Table of Isotopic Ages of Mesozoic Volcanic Rocks in Northeast China
① According to Peng Yu Whale (1995), slightly modified; * k-ar, * * ar-ar, * * u-Pb, other Rb-Sr; Age unit: horse.
(1) The attribution of magmatic activity stages in Early and Middle Triassic.
At present, it is known that the granite intrusions formed in the early and middle Triassic in this area are mainly distributed in the eastern part of Jihei, namely Xiaoxing 'anling-Zhangguangcailing granite belt (Li Zhitong et al., 1988, 199 1). Although the geological history is long, its main body was formed from late Paleozoic to early Mesozoic. In terms of structural development, syntectonic and late-movement granitoids were formed from Permian to early Triassic, and post-structural granitoids were formed from the end of early Triassic to middle Triassic. Mainly A-type granitoids with isotopic ages of 232 ~ 265,438+07 Ma (Rb-Sr, U-Pb) (Li Zhitong et al., 65,438+0992,65,438+0994; Peng Yujing et al., 1995). At the same time, the Lower Triassic Lujiatun Formation (T 1l) belongs to the molasse deposit in a foreland-like basin, and the black fine clastic rock at the top of it is (239 9.5) Ma (Rb-Sr) (Xia Mingxian et al., 1987), and the timely feldspar fine sandstone in the upper layer belongs to the mature continental crust, which indicates a stable deposit. The intrusion of alkaline magma marks the maturity of the crust and the end of orogeny (He,1989; David Hong et al., 1994).
To sum up, the early and middle Triassic granitoids in this area are the products of late Paleozoic tectonic magmatic cycles. The alkaline complex in Marseille, Liaoning Province was also formed in a relatively stable extensional environment in the early and middle Triassic under the mechanism of late Paleozoic tectonic magmatism (Yan Guohan, 1989). Therefore, this part is not included in the description of Mesozoic magmatic activities in northeast China.
Table 2-3 Comparison of Isotopic Ages of Mesozoic Granites in Northeast China
① According to Peng Yu Whale (1995); *K-Ar, **U-Pb, and the rest Rb-Sr; Age unit: horse.
(2) Late Triassic magmatic activity
The establishment of Late Triassic volcanic magmatism in this area began in the late 1970s, and the Late Triassic volcanic rock series was discovered in Yanbian area of Jilin Province (Wu et al., 1980). Subsequently, modern volcanic rocks and some late Indosinian granitoid intrusions (Liu,1981; Peng Yujing,1982; Wang Youqin et al.,1983; Li Zhitong et al.,1988; Ma Jiajun et al., 199 1). Data show that the Late Triassic magmatism played an important role in the development of Pacific tectonic geology in the northeast coast of China (Li Zhitong et al., 1988).
1. Late Triassic volcanic rock series
Based on the discovery of plant fossils in sedimentary interlayer between volcanic rocks (Wu et al., 1980), Daxinggou volcanic group (T3d) was first discovered in Yanbian area, with isotopic ages of 196Ma(K-Ar) and 2 10.03 Ma (Rb-Sr) respectively. The volcanic group of Laoheishan (T3l) discovered later also contains fossils such as cycads, with Rb-Sr age of 23 1.03Ma and Rb-Sr age of Suifenhe volcanic series of 208Ma. The Rb-Sr age of the volcanic rock series of Nanloushan Formation (T3n) in central Hebei Province is (222 10)Ma, which was unconformity covered by the Lower Jurassic Yuxingtun Formation (J 1y) (Li Zhitong et al., 1994). Xitushan Formation (T3x) is similar, with Rb-Sr age of (2 10 19) ma. Predecessors have obtained 2 1 K-Ar ages in the corresponding volcanic strata, ranging from190.8 to 226.2 ma. It can be seen that Rb-Sr age is roughly consistent with K-Ar age.
2. Late Indosinian granitoids
The first granite body with conclusive evidence is the Nozhigou monzonite body, which intruded into the Laoheishan Volcano Group (T3l) and the 72- T granodiorite body (zircon model age 254Ma) in the late Variscan, and was unconformity covered by the Dongning Formation (J3d) of the Upper Jurassic, with zircon model age 189 Ma and Rb-Sr age (206.7 2. There are also some granitoids in the same tectonic belt, which also belong to the late Indosinian period, such as Laotudingzi rock mass (Rb-Sr, (197 10) Ma) in baishan city and Lishugou rock mass ((2 15 26) Ma, Rb) in front of Fushun Nankou rock mass. K-Ar ages of these rocks are 65438 086 ~ 265438 04ma. They formed a volcano-granite belt with volcanic rocks of the corresponding era, which the author called Taipingling-Changbai Mountain Belt (Li Zhitong et al., 1988). In fact, the rock belt can reach Raohe area in the northeast corner of Heilongjiang Province to the north and Fushun area of Liaoning Province to the south.
Wudaoliuhe pluton in the southeast of Jiapigou, central Hebei Province intruded into Archean granite and Upper Triassic Xiaoyingzi Formation (T3x), and was covered by Jurassic Shiren Formation (J3sh), with zircon ages of 20 1.5Ma and 192Ma respectively (Liu Dazhan et al., 1994). The Xinkaihe rock mass in Panshi intruded into the volcanic rocks of Nanloushan Formation (T3n) and was covered by glutenite of Yuxingtun Formation (J 1y). The K-Ar dilution age of muscovite in Maoshan muscovite granite is 265438±03.5ma. In addition, granite intrusions are accompanied by gabbro and diorite small rocks.
3. The age of formation and emplacement of Nadanhala ophiolite.
According to the research (Kang Baoxiang et al., 1990), the Raohe ophiolite in Nadanha Daling is developed in the Mesozoic geosyncline fold belt in eastern China, and consists of relatively complete mafic and ultramafic accumulation complexes and pillow lava (see later). Located in the sandstone slate of Dalingqiao Formation (T3-J 1d), the latest stratum in the geosyncline sedimentary age in this area is Yongfuqiao Formation (J 1y). The subduction age of the oceanic crust in this area occurred in the middle and late Early Jurassic, so the emplacement age of ophiolite is Early Jurassic, which should be earlier than Dalingqiao Formation (T3-J 1d). According to the consistency of geochemical characteristics between pillow lava and basic ultrabasic rocks sandwiched in geosyncline sediments (Dalingqiao Formation), there is a genetic relationship between them, so it is speculated that the ophiolite age is middle-late Triassic.
(3) Early Jurassic magmatic activity
Early Jurassic volcanic eruption activity in northeast China was weak, and the distribution of volcanic rocks was limited. Granite intrusive rocks are exposed in western Liaoning.
The volcanic age of the early Jurassic volcanic system Xinglonggou Formation (J 1x) is mainly based on the overlying fossils of the lower Jurassic Beipiao Formation (J 1b). Its isotopic ages are (198.5 2.5) Ma (Wang Dongfang et al., 1984b)(Rb-Sr) and (199.5 9.8) Ma (K-Ar isochron) (Diao Naichang et al.,/kloc-). The surface ages of K-Ar are 22 1.6Ma, 2 10.8Ma, 204.8Ma, etc. In the southwest of Huludao City, the K-Ar age of Jianchang granite invading the volcanic rocks of Xinglonggou Formation is 214 ~196ma; In addition, the basement conglomerate of Upper Triassic Yangcaogou Formation (T3y) in Beipiao Yangcaogou contains andesite gravel (Wang et al., 1989). To sum up, it is reasonable to suspect that Xinglonggou Formation, like Xingshikou Formation (T3-J 1x) in neighboring Hebei Province (Hebei Bureau of Geology and Mineral Resources, 1989), may have the Late Triassic-Early Jurassic era. There are volcanic clastic rock series of Yuxingtun Formation (J 1y) in central Hebei, including andesite and dacite, which can be regarded as the aftermath of volcanic activity in Nanloushan period, and its Rb-Sr age is 184.7Ma, which is slightly lower. Gaolingzi Formation (J 1g) and Nandashan Formation (J 1n) are exposed in the east of Heilongjiang Province, which are andesite, rhyolite dacite and their clastic rocks respectively. The former was placed in early Jurassic because of its siliceous gravel in late Triassic; The latter is related to the Late Triassic strata, with K-Ar age 1.76Ma, and is temporarily located in the Early Jurassic (Heilongjiang Bureau of Geology and Mineral Resources, 1.993).
Early Jurassic granitoids are widely distributed and often associated with late Triassic and early Jurassic volcanic rocks. ① There are granites in the south of western Liaoning, such as Soda Factory, Jiumen, Yangjiazhangzi and Shengzong Temple. The latest intrusive stratum is the Lower Jurassic Xinglonggou Formation (J 1x), with the age of 2 14 ~ 188 Ma (k-Ar) and 2 1 1 ~ 6558. Wang et al., 1993). ② The surrounding rocks of Changgangling and Qiancuoluo granodiorites in Daheishan molybdenum mine in central Jilin Province are metamorphic rock series of Toudaogou Formation (Pz 1t) and volcanic rock series of Nanloushan Formation (T3n), with ages of 180.8 and 185Ma(U-Pb isochron) respectively, and K-Ar of Congdingzi rock mass in Dahan. ③ The Rb-Sr ages of Beigou and labyrinthine adamellite in Yanbian area are (196.5 6.9) Ma and 192.9Ma, respectively, and the Rb-Sr age of Huanggou syenite is 195Ma. From the geological environment, Beigou pluton is associated with Daxinggou volcanic rock series (T3d), while Huanggou pluton is covered by Tuntianying Formation (J2t). Its time limit is between Late Triassic and Middle Jurassic. ④ The Hamahe granodiorite in Raohe, Heilongjiang Province intruded into the ophiolite pillow lava and siltstone of the lower Jurassic Yongxing Bridge Formation (J 1y), and the K-Ar age 189.3Ma (Kang Baoxiang et al., 1990).
It seems reasonable that some people divide the late Triassic and early Jurassic magmatic activities in this area into a magmatic activity period or a magmatic activity cycle (Peng et al., 1997).
(4) Middle Jurassic magmatic activity
Middle Jurassic volcanic rocks are developed in western Liaoning, central Jilin and Yanbian, but less in eastern Heilongjiang and Daxinganling. At the same time, granite is widely exposed.
Middle Jurassic volcanic rock series. Tiaojishan volcanic rock (J2t) is widely distributed in western Liaoning, belonging to the Middle Jurassic (Cao, 1982), but some people put it between the Middle Jurassic and the Late Jurassic, which is consistent with the existing age data: K-Ar isochron age (156.3 8.5) Ma, Rb. Guo, 1992). The achievement in recent years is (167.2 9.7). Ma-(140.02.0) Ma (Chen Yixian et al., 1997). The Rb-Sr age of the volcanic rock series of the middle Jurassic Haipanggou Formation (J2h) is177.2ma; ; There is a small amount of acid lava in the Zhongnan Duan Xinmin Formation (J2x) in Daxinganling. The volcanic rocks of Tuntianying Formation (J2t) are widely distributed in Yanbian and Dongning areas. Its 40Ar-39Ar age is 170.0 ~ 176.3ma in Hedgehog Gold Mine. Rb-Sr age of acid volcanic rocks in Boli volcanic basin of Heilongjiang Province is 162.3 ~ 173.8 Ma, all of which are products of Middle Jurassic.
Middle Jurassic granitoids. It is widely exposed in this area and intruded into the middle Jurassic and older rock strata, which is supported by isotopic age. ① The Laojiaogou rock mass in central Hebei is 163.5Ma(U-Pb isochron); Chaihe rock mass takes170.1ma (u-Pb); Rb-Sr age of Daheishan porphyry is 175.3Ma (Fang Wenchang, 1992). ② Weizigou rock mass in Yanbian intruded into the late Variscan rock mass and was covered by the Lower Cretaceous, with Rb-Sr age of170ma; ; Miaoling rock mass is covered by Lower Cretaceous, 16 1Ma(K-Ar) (Fang Wenchang, 1992). ③ In eastern Heilongjiang, Rb-Sr ages of Ergu rock mass and Songfengshan rock mass are 177.8Ma and170 Ma, respectively; , respectively; Ning 'anwang Baneke pluton 169Ma (zircon U-Pb); Lin Xiaoxi rock mass 165 Ma (Rb-Sr); Sunwu Sanchahe Rock Mass 169.5Ma(Rb-Sr) (Heilongjiang Provincial Bureau of Geology and Mineral Resources, 1993). ④ Xinjinmiaoling rock mass in Liaodong is180ma (u-Pb); ⑤ Xiaojiayingzi diorite body in western Liaoning is176.5438+0ma (k-ar); The K-Ar ages of the Shajingou rock mass are 163.6,161.2ma.. ⑥ The rock mass in Banshantu of Daxing 'anling is169ma (k-ar); Rb-Sr ages of Budunhua pluton and Ketu pluton are 65438 066 and 65438±064ma, respectively.
(5) Late Jurassic-Early Cretaceous magmatism.
Late Jurassic to Early Cretaceous is the period of the strongest Mesozoic magmatism in northeast China, and its eruptive or intrusive products are also the most widely distributed. It is rich in animal and plant fossils, indicating that its biostratigraphic age is from late Jurassic to early Cretaceous. Judging from the volcanic rock series, its formation is diachronic and shows the characteristics of continuous evolution.
1. Late Jurassic-Early Cretaceous volcanic rocks in western Liaoning.
The volcanic rock horizon of Yixian Formation (JBOY3 -K 1Y) has always been controversial (Liaoning Bureau of Geology and Mineral Resources,1989; Wang et al; Cao,1982; Zang Yaoling et al., 1993), a large number of age data show that its age really belongs to the late Jurassic to the early Cretaceous: Rb-Sr age 142.5Ma, 127.0Ma and 125.9 Ma, K-Ar isochron age/kloc-. Diao Naichang et al.,1983; Zhang Zhaochong et al., 1993), 40Ar/36Ar isochron age 144.0Ma,1/5.0ma [43]. At present, Yixian Formation has been represented by J3 -K 1y in the regional scale of150000.
2. Late Jurassic-Early Cretaceous volcanic rocks in Daxinganling.
The Rb-Sr ages of Manketou Aobao Formation, the lower subgroup of late Jurassic Xing 'an Mountains in south-central China, are 160Ma, and those of Laobai Asphalt Formation are 149.5Ma (Rb-Sr), 145.55Ma (U-Pb),/kloc. The late Jurassic volcanic rocks in the northern section are 144.64Ma(Rb-Sr) and 144.5Ma(K-Ar isochron), the early Cretaceous volcanic rocks are 1 13.57 Ma, and the K-Ar isochron is/kloc-0.
3. Late Jurassic-Early Cretaceous volcanic rocks in eastern Jilin and Heilongjiang.
Rb-Sr ages of Yanbian hedgehog and Diyingou late Jurassic volcanic rocks are 149Ma and 144Ma, respectively, and Rb-Sr ages of early Cretaceous volcanic rocks are130ma. . Rb-Sr ages of early Cretaceous Yingchengzi Formation (K 1y) in central Hebei are 130Ma and 125Ma(Rb-Sr), respectively (Zhao Chunli et al.,1996); The volcanic rocks in the upper part of Didao Formation in Jixi (J3d) and the bottom part of Chengzihe Formation (K 1c) are 146.7Ma and 144.2Ma(K-Ar) and 139.4Ma(Rb-Sr), respectively. The K-Ar dilution age of contemporary volcanic rocks in Bindong is 139.4Ma (Heilongjiang Bureau of Geology and Mineral Resources, 1993).
4. Late Jurassic-Early Cretaceous granitoids
Relating to or invaded by contemporary volcanic rocks, widely distributed. ① Rb-Sr ages of Luohongshan rock mass in western Liaoning are 154.0Ma, Xialanjiagou rock mass is 148.4Ma(K-Ar), and Lushan rock mass is 153.8Ma(U-Pb coincidence line) (Zhongruiyuan,1990; Su Chuanyu et al., 1994). ② Rb-Sr ages of Ma 'anzi, Er04, Baishilazi, Baiyinnuo and Dongshan Bay in the middle-south section of Daxing 'anling are 155.4, 142, 142.05, 148 and134, respectively. Rb-Sr ages of the rocks on the right bank of Ergon and Nianzishan in the northern section are 154.5Ma and 139Ma (Zhang Baocheng,1989; Li Peizhong. ). ③ The U-Pb isochron ages of Shuangyazi and Dajiashan rocks in central Hebei are 147.8Ma and 150Ma, respectively, and the U-Pb isochron ages of Dongjiazi rocks are 159.5Ma(K-Ar) (Fang Wenchang, 1992 ④ The U-Pb ages of rocks in Mayihe and Lanheshan in southern Jilin-Liaodong are 147.7Ma and142 Ma, respectively; They are; The K-Ar ages of Huatong and Longwanzi plutons are 154.2Ma and135.2ma respectively. ⑤ In Bindong, the Rb-Sr ages of Gongpengzi and Erlongshan are 148Ma and 138Ma respectively, and the K-Ar ages of Sanqing and Heilonggong are/kloc respectively. ⑥ The K-Ar ages of some granitoids in Xunke, Nenjiang and Tayuan in northern Heilongjiang are 149Ma, 140Ma and 130Ma, respectively.
(6) Cretaceous magmatic activity
Including magmatic activities from the middle and late Early Cretaceous to the late Cretaceous, with a time limit of 120 ~ 65 Ma.
1. Cretaceous volcanic rocks
The K-Ar age of volcanic rocks corresponding to the Daxing Zhuang cycle in the middle and late Cretaceous in western Liaoning is 1 15 ~ 80ma (Zhang Zhaochong et al.,1993); The Rb-Sr age of early Cretaceous volcanic Xiaoling Formation (K 1x) in Liaodong is 98.9Ma, and the corresponding horizon is Late Cretaceous Sanshu Formation (K2S) in southern Jilin, with K-Ar ages of 77.9 1Ma and 84.85Ma；, respectively. The Rb-Sr age of rhyolite in An Ying, central Hebei Province is 65438±008ma；. ; The four K-Ar ages of volcanic neck facies rocks in Diyingou, Yanbian area are 1 17.95, 102.56, 97.3Ma and 95.25Ma respectively. K-Ar ages of the Early Cretaceous volcanic Dongdaling Formation (K 1d) in eastern Heilongjiang are 107, 104, 10 1Ma and 96Ma, respectively. The Ou Ken River Formation (K2o) in the northern Daxing 'anling Mountains is a set of late Cretaceous acidic volcanic rocks.
2. Cretaceous granitoids
K-Ar ages of biotite granite associated with or invaded by Cretaceous volcanic rocks in Shaoguoyingzi area, western Liaoning Province are 1 16.0,10/0.5ma and 910.8ma, respectively. ; In Jinan-Liaodong, the zircon U-Pb ages of three alkaline granites in Fushun are 107 and 96Ma (National Isotopic Geological Age Data Compilation Group, 1983), the zircon U-Pb ages of Jijiapuzi alkaline granite and Dingqishan alkaline granite in Dandong are1/6.9. In Jiamusi area of Heilongjiang Province, some ultra-shallow small rocks are also the products of this period. The K-Ar age of Huabaoying diorite porphyry in Luobei is 92Ma, and the zircon U-Pb ages of granite diorite porphyry in Tuanjiegou gold mine in Jiayin are 1 14Ma and 105Ma, and the zircon U-Pb ages of associated dacite porphyry are also 105Ma. The Rb-Sr isochron age of Xiaobielakeng adamellite in Raohe River is 1 18Ma. Th-Pb ages of the monazite in Hulingou in the east of Mudanjiang are 103.8 and 89.3Ma, and the Th-Pb age of the monazite in Baoqing Yongfeng is 98Ma.
(7) Cenozoic magmatism
Cenozoic magmatism in Northeast China is also very active. Existing geological and isotopic age data show that volcanic eruptions occurred in Paleocene, Eocene, Oligocene, Miocene, Pliocene to Pleistocene and Holocene, and even volcanic eruptions were recorded in Changbai Mountain and Wudalianchi in15 ~17th century. Liu Jiaqi (1988) divided it into 10 scenes: ① Datun volcanic curtain (β K2-E 1, 86 ~ 6 1ma) and ② Shuangliao volcanic curtain (β E 1, 49 ~ 39ma). 23 ~ 19ma), ⑤ Nitoushan volcanic curtain (16 ~ 13ma), ⑤ Laoyeling volcanic curtain (1 1 ~ 7ma), ⑦ Warship Mountain volcanic curtain (β N2, 4.5 ~ 2.66). In particular, the Eocene alkaline rock intrusion was discovered in Huadian, Jilin [39]; There are even Pleistocene aegirine alkaline granite rocks in Changbai Mountain area.