Granite, as one of the most widely recognized rocks on earth, is distributed in various tectonic environments. However, granite is not as important as basalt as a marker of tectonic setting for two reasons: (1) it is difficult to collect samples of granite from known tectonic settings, i.e., it is often difficult to obtain precise geological evidence of the tectonic setting of the intrusion of these rocks before they are exposed on the surface; (2) the diagenetic history of granite is more complex, e.g., the crystal accumulation and the mixing of crustal materials have made the important geochemical characteristics of granite obscure. Pitcher (1993) pointed out that granite types are widely associated with geological environments, and different tectonic environments will provide different source rock assemblages and produce different formation processes, and he believed that S-type granites were formed in the intracratonic and continental collisional orogenic zones; high-K, low-Ca I-type granites were formed in the post-orogenic uplift environments; and low-K, high-Ca I-type granites were formed in the active continental margins; A-type granites were formed in the postorogenic uplift environments; and low-K, high-Ca I-type granites were formed in the postorogenic uplift environments. active continental margins; A-type granites are produced in stable orogenic belts, Craton uplift and rift valleys, which are non-orogenic environments; and M-type granites are produced in oceanic island arc environments. However, Pearce et al. (1984) believe that there is no clear boundary between the S, I, A and M granites, and there is not always a simple correspondence between them and the tectonic environment. Although there are more scholars using the geochemical illustrations to determine the tectonic environment of granite formation, this method has been opposed by more and more scholars, because the geochemical composition of the rocks mainly depends on the composition of the source rocks, the physicochemical conditions of melting and the later diagenetic process, and is not directly related to the geotectonic background. Therefore, the study of rock assemblages and the physicochemical conditions of rock formation should be a more effective way to trace the tectonic background at the time of rock formation by excluding the influence of later geologic effects (Deng Jinfu et al., 1996), but in this book, we mainly utilize the regional geologic data to examine the tectonic controls on the formation of granites.

1. Conversion of the Paleo-Asian-Pacific tectonic domain

The geologic evolution of the Northeast region has undergone an extremely complex history, and the evolution of the Paleo-Asian domain in the Paleozoic era basically laid down the tectonic framework of the region (Sengor and Natal'in, 1996), but the Pacific domain of the Meso-Cenozoic era has had an important influence on the region. It is mainly manifested in the collage of a series of different age bodies and the development of the strike-slip tectonic system at the eastern margin, while a series of basins and a large area of magmatism were developed at the back margin (Zhao Yue et al., 1994; Wang Xinwen, 1997). Although a series of new insights have been gained from their study, the timing of the transition between the paleo-Asian and Pacific tectonic regimes has been debated (Shao et al., 1997; Li Jinyi, 1998), and this issue actually involves the origin of the paleo-Pacific Ocean. The main reasons for this debate are the disagreement over the properties of the products of geological action during this period, on the other hand, the relatively limited geological construction available for study, and the fact that the transformation of the tectonic domain could not have been completed in a relatively short period of time, but may have been a developmental evolutionary process. Although we believe that the final closure of the Paleo-Asian Ocean occurred in the late Late Paleozoic-early Early Mesozoic, a series of Late Yanshanian events on the northern margin of the North China Platform still implies that it was related to the evolution of the Paleo-Asian tectonic domain, reflecting the intra-terrestrial continuation effect after orogeny.

In the case of this study area, the essence is how to interpret the tectonic properties of Indo-Chinese rock building. Although only one Late Triassic granite body has been identified in this study area, the number of granites in this period is very large from the viewpoint of the Xiaoxing'anling-Zhangguancailing and Yanbian areas in the north (Sun Deyou, 2001; Zhang et al., 2004), and from the viewpoint of the spatial distribution, they are characterized by facies spreading. Therefore, the Late Triassic granites with facies distribution are completely different from the igneous rocks formed by plate subduction with parallel trench banding, and granites of this period occur in Daxing'anling, which is more than 1,000 kilometers away from the Pacific Trench. We believe that the Late Triassic granites in the eastern part of the Xingmeng orogenic belt (including the present study area) were formed in the tectonic context of the disappearance of the Paleo-Asian Ocean and the collision of the two major north-south plates in the Late Permian-Early Triassic, and belonged to the post-orogenic tectonic environment, which is in complete agreement with the fact that the Sandaohe body in this area belongs to the A2 type. The specific rock formation mechanism is, in the collision of mountain building after the lithosphere demolition and sinking caused by the mantle source magma bottom erosion background, high temperature mantle source basaltic magma bottom erosion in the bottom of the lower crust, which brings a lot of thermal energy, caused a large area of the pre-existing basaltic crust partially melted to form granite magma.

The Hongqiling Mg-Fe-Super Mg-Fe rocks located in the Hulan Town area of Panshi County, Jilin Province, are one of the most important sources of Cu-Ni deposits in China, and it was previously believed that these rocks were formed in the Early Paleozoic or at least the Early Late Paleozoic. However, our latest SHRIMP age data show that it actually formed during the Indo-Chinese period; the Drift River rock body to its east was produced in the form of rock veins (more than 150 veins), which are the same age as the Hongqiling rock body. Detailed geochemical studies confirmed that these rocks originated from the crystallization of high-magnesium basaltic magmas (Wu et al., 2004b). Therefore, combining the results of geological and geochemical studies, these rocks should have originated from the partial melting of the lithospheric mantle caused by high temperature, and the most favorable tectonic background for this melting to occur is the dismantling and sinking of the lithosphere after the orogeny.

Therefore, the appearance of A2-type granites in the Indo-Chinese period marks the formation of these granites in the post-orogenic environment and the end of the collision of the north and south plates in the orogeny, and the large-scale appearance of magnesian-ferrous-supermagnesian-ferrous rock bodies (216 Ma) in Hongqiling and Drift River (Wu et al., 2004b) in the same period also the end of such orogeny and the occurrence of the clathrate, which represents the final consolidation of the East Asian continent. The final consolidation of the East Asian continent also marked the end of the influence of the Paleo-Asian tectonic domain on the region, and the transition to the development of the Pacific tectonic domain. However, it must be pointed out that the development of A-type granite in this period may last until the Jurassic, forming the Tianqiaogang A-type granite studied in this book.

2. Collage of the Jiamusi Massif and the beginning of the Paleo-Pacific Tectonic Domain

Research on the timing of the beginning of the Paleo-Pacific Tectonic Domain is still quite limited. The complex ocean-land pattern of the region during the Late Paleozoic-Early Mesozoic, coupled with the collage and rotational deformation of the tectonic blocks in the later period, makes it impossible to judge the time of the beginning of the Pacific tectonic domain simply by the direction of the present tectonic line. It is generally believed that the existence of Late Paleozoic rock building in the eastern part of the Jiamusi Massif may reflect the existence of a subduction regime in this area (Li Jinyi, 1998), which is a product of the Pacific Rim tectonic domain, but the lack of precise chronological data makes it difficult to make a definite judgment on this at present.

On the other hand, most scholars believe that the continental margin of East Asia underwent a qualitative transformation during the Mesozoic. According to the findings by means of magnetic anomaly strips on the seafloor and other means (MaruyamaandSeno, 1986;Maruyama, 1997), passive continental margins predominated in our region during the early Mesozoic, but our dendrochronological data show that strong magmatism and concomitant active continental margins existed in Northeast Asia at that time, at least from the beginning of the Jurassic, a realization that comes mainly from our recent knowledge of the Heilongjiang Group.

The Heilongjiang Group is a set of rock assemblages located along the Mudanjiang Fracture dominated by blue gneisses (including shallowly metamorphosed basaltic rocks), dacites, and ultramagnesian ironstones (Fig. 4-31), and although the Heilongjiang Bureau of Geology and Mining (1993) has done in-depth work on its stratigraphic sequences, it is now basically believed to be a suite of ophiolitic green mélange rocks representing the collocation of the Jiamusi in the east with the Songnen Massif in the west (Yimian), and a combination between the Jiamusi and Songnen Massifs in the west (Yimian). The Heilongjiang Group is now largely believed to be a set of ophiolite mélange, representing the collocation between the Jiamusi on the east and the Songnen Massif on the west (Yan et al., 1989; Zhang Yiman et al., 1998). The question remains, however, when the high-pressure blue schist phase metamorphism of the Heilongjiang Group occurred. Previous chronological data suggest that this type of metamorphism may have occurred in the Early Paleozoic and corresponds to the so-called Garidong granite event in the Zhang Guangcai Ling area to its west (Zhang Xingzhou, 1992), but the credibility of the original data has not been confirmed. Subsequent dating of the blue schists in the Mudanjiang area yielded Mesozoic age data (Yeh Hui-Wen et al., 1994; Li Jin-Yi et al., 1999), but they were mostly interpreted as late tectonic disruptions of the Dumi Fault. In the central Yilan area, Rb-Sr mineral isochron ages around 185 Ma were also previously obtained by the Heilongjiang Geological and Mining Bureau, but were also disregarded because of the suspicion that they might be an effect of the Jiayi Fault.

In order to clarify the time of metamorphic deformation of the blue schist phase of the Heilongjiang Group, we collected mica-bearing gneisses that underwent deformation in the Luobei area for mineral Rb-Sr isochron ages. The protolith of this rock is granite, and the zircon age shows an intrusion age of 265 Ma, which is consistent with the age of the large granite in the Jiamusi Massif, but the Rb-Sr mineral isochron age of mica is 184 Ma, which is exactly the same as the same type of chronology in the Yilan area. This preliminary information suggests that previously obtained Mesozoic ages for the Heilongjiang Group may be of extreme importance.

In order to further verify the reliability of the Mesozoic age of the Heilongjiang Group, we have recently carried out age determinations of mica schists in the Heilongjiang Group at the National Taiwan University using the university's Ar-Ar equipment (Wu et al., 2007a). The results show that the blue amphibole in the blue schists along the Millstone did not give a desirable age because of the small grains; the age of the black mica in the mica in the Yilan area is only about 60 Ma, but the age of the white mica is about 175 Ma. If the particle laser method is used, the age of its occurrence in the high-temperature phase is 195 Ma. Considering the closure temperatures of the Ar-Ar systems of the different minerals, we believe that 175-195 Ma should represent the age of the metamorphism of the blue schist phase in the area. Similarly, similar samples from Tuanshanzi, Huainan, and Luobei areas give ages of 175-185 Ma. Therefore, we are basically certain that the Heilongjiang Group, which tabulates the collocation of the Jiamusi and Songnen Massifs, is an ophiolitic green mélange formed in the Early Jurassic of the Mesozoic. In connection with the end of the Paleo-Asian tectonic domain discussed earlier, we believe that Jiamusi should belong to the accretionary bodies of the Pacific Rim Belt.

Figure 3-43 Distribution map of the Heilongjiang Group and the accretionary body of the Jurassic active continental margin in eastern Asia (according to Wu et al., 2007a)

Corresponding to the above events is the development of a large number of Jurassic granites in the region, with quartz syenite and granodiorite dominating the rock types, and the tectonic attributes of which are very similar to those of the present-day east coast of the Pacific Ocean, although the age of the rocks are not developed in the Jiamusi Massif (Figure 3-43). Therefore, we hypothesize that an active continental margin existed at that time in the Zhang Guangcai Ling area west of the Jiamusi Massif, which should at least represent the beginning of the Paleo-Pacific tectonic domain. From a larger spatial perspective, the Early-Middle Jurassic granitoids spread over the areas of South China, Jiaodong, Liaodong, Yanliao and Yanbian in eastern China (Wu et al., 2005b), undoubtedly as a result of the influence of the Pacific Plate.

From the above, combined with the fact that the Jurassic magmatism in Northeast China exhibits the same rock assemblage and compositional characteristics as the active continental margins, it reflects an extruded geotectonic background in the region. In addition, some scholars think that the Jurassic evolution of the region may be related to the Mongolia-Okhotsk belt in the north, but the seismic stratigraphic data published so far show (van der Voo et al., 1999) that this tectonic belt was subducted northward during the Mesozoic, and that there is a long time interval between the Mesozoic and the end of orogeny of the Xingmeng orogenic belt in the region, and the other reason put forward by those who hold the opposite opinion is that Another argument put forward by the opponents is that there was no plate subduction system in eastern China at that time, and that it might even have manifested itself as a passive continental margin, but this argument does not coincide with the results of the current studies in the Japanese archipelago. According to studies in the last decade, the major blocks that made up Japan were located in the eastern part of the Tohoku region before the opening of the Sea of Japan at about 20 Ma. Currently, there are more reliable data suggesting that the Hida and Kitakami bodies in Japan may be the extension of the Paleozoic geologic bodies in this region (Otoh et al., 1990; Tazawa, 1992, 1999, 2002; Arakawa and Shinmura, 1995). At the same time, a large number of Jurassic accretionary mafic rocks exist in Japan (Isozaki, 1997; Taira, 2001), and some of the mafic rocks of relatively recent age are consistent with similar geologic bodies in Nadanhada, China, and the Russian Far East (Koji-ma, 1987; Parfenov, 1993; Popova et al., 1999; Zyabrey and Matsuoka, 1999; Sato et al. 2002; Hanczyk and Feripov, 1993). Since there are fewer seafloor magnetic anomalies available to constrain the age of formation of the Pacific Ocean (Hilde et al., 1977; Engebreston et al., 1985; Maruyama and Seno, 1986; Bartolini and Larson, 2001), we should give more consideration to specific geologic record conditions.

3. Early Cretaceous crustal evolution

The Late Mesozoic Early Cretaceous geotectonic evolution of the Northeast is one of the most perplexing basic geologic problems at present. Although some scholars believe that the Cenozoic geologic evolution of the region is related to the convergence of the Indo-Eurasian plate (Molar and Tapponnier, 1975, 1977), there is not much evidence for this claim at present (Northrup et al., 1995), and therefore we believe that the subduction of the Pacific plate may have been an important factor constraining the Cenozoic geologic development of the region . For the Late Mesozoic, however, the problem is more complex. The main geologic structures formed during this period are the widely distributed volcanic rocks and granites and the Songliao Basin, which is flanked on the east by a series of NNE-trending strike-slip fractures, such as the Dunhua-Mishan Fault and the Jiamusi-Yilan-Yitong Fault, which have also basically shaped the major geotopographic and lithospheric tectonic units of the present Northeast China.

On the whole, there are currently three views on the mechanisms controlling the Late Mesozoic tectonic evolution of the region. One is that it is related to the subduction of the eastern Pacific plate (Uyeda and Miyashiro, 1974; Hilde et al., 1977; Takahashi, 1983; Deng Jinfu et al. 1996; Zhu Qinwen et al. 1997), and that the existence of the Mesozoic ophiolites in the Nadanhada area is an important manifestation of the existence of the above tectonic regime. However, the opposing view is that even if the subduction system exists in the eastern part of the region, it is too far away from the Daxinganling; the second view is that it is related to the southward subduction of the Mongolian-Okhotsk Sea in the north (Wang et al., 2002), or to the post-orogenic evolution of the Xingmeng orogenic belt (Lin Qiang et al., 1998); the third view is that the Late Mesozoic in the region was dominated by extensional action and controlled by the mantle column with an independent evolutionary mechanism. The third view is that the Late Mesozoic was dominated by extensional processes, controlled by the mantle column tectonics or intra-land tectonic system with independent evolutionary mechanisms (Shao et al., 2001). The main reasons for the failure to reach convergent conclusions on the above issues are: first, the age of the Daxinganling volcanic rocks is unclear; second, the formation mechanism of the Songliao Basin is not known, and it is still difficult to give a definite answer to the above questions with the data accumulated in recent years. Our hypothesis is that the event is related to the evolution of the Pacific Ocean, but the specific tectonic background should be stretching in nature. This hypothesis is mainly based on the following evidence.

1)Uniformity of Early Cretaceous magmatism in eastern China:It is no coincidence that 120-130 Ma magmatism is not only extremely developed in northeast China, but also occurs over a large area in Jiaodong, the eastern part of the Yangzi Massif, and southern China in eastern China (Wu et al., 2005a). Although we can have several explanations for this feature, the simplest explanation is that their formation is controlled by the eastern Pacific system.

2)Early Cretaceous magmatism is related to contemporaneous metamorphic core clasts:During the Early Cretaceous, a certain number of metamorphic core clasts developed in eastern China, of which a representative example is the Liaonan metamorphic core clast located in the southern part of Liaodong. The heterolith is located on the east side of the Tantanlu Fracture, which consists of the Jinzhou Fracture Zone, the Paleozoic-Mesozoic sedimentary rock cover, and the Early Cambrian metamorphic rocks (nuclei), etc. The Early Cretaceous granitic rocks are the most important ones in China. Among them, the Early Cretaceous granitic intrusive body is intruded along the Jinzhou detachment fault zone, and the main rock bodies are Gudaoling, Wanjialing, Miaoling, Drinking Horse Bay Mountain and Qixingtai. These bodies are clearly multi-phase and can be divided into central and marginal phases according to petrography. The center phase lithology is mainly black mica diorite and black mica granite, the rock is medium-grained granite structure, block structure, the rock overall no deformation; edge phase is mainly granodiorite, suffered from strong deformation, mostly gneissic. The facies is identical to the facies in the ductile shear zone, which is a homotectonic rock body. Our zircon U-Pb dating reveals that the intrusion of these rocks mainly occurred between 118 and 129 Ma (Wu et al., 2005a; Guo Chunli et al., 2004), which is consistent with the age of the activity of the detachment faults, and is a strong evidence for the formation of granites in an extensional context.

3)Extensive development of Early Cretaceous A-type granites:A large number of A-type granites were formed in the Early Cretaceous in Northeast China. In the Daxinganling area, there are Balzhe, Mianzishan, Wuduhe, Solun, etc.; in the Zhangguancailing area, the rock bodies of this period are Baishileizi, Qingyangweizi, etc.. In the Liaodong Peninsula in the south of the region, there are Qianshan and Sipingjie rock bodies. In fact, in the Tonghua area east of the Liaodong Peninsula, there are nearly ten rock bodies of A-type granite represented by the Gangshan rock body. In the Yanliao belt, A-type granite bodies such as Shanhaiguan, Ringshan, Qianlianbei, Wulingshan, Gulingshan, and Ashan have been identified so far. The work in recent years shows that almost all the A-type granites in the zone were formed during 120-130 Ma, at the same time as the widely distributed I-type granites. Therefore, we have reason to believe that the evolution of the Northeast region in the Early Cretaceous was related to the extensional regime.

Based on the above considerations, we believe that the Early Cretaceous evolution of eastern China, including Northeast China, was mainly controlled by the subduction orogeny and post orogenic evolution of the eastern oceanic plate, and that the convergence of the plates in the early stage led to the thickening of the lithosphere and the occurrence of magmatism in the nature of active continental margins, and that the thickened lithosphere subsequently underwent dismantling and downsloping and the direct contact between the soft-fluvial mantle and the crust appeared to the east of the region. The unique geological phenomenon of direct contact between the mantle and crust of the asthenosphere occurs in its eastern part. The kinetic effect of the direct contact between the soft flow mantle and the crust is to produce a strong magma plate bottom cushioning effect and the accompanying high-temperature metamorphism of the deep crust and part of the melting effect, the formation of a huge amount of magma intrusion and eruption, which is the reason for the formation of the Early Cretaceous granite.