Characteristics of magmatic rocks in different periods

With the periodic activity of the structure, magma overflowed and invaded in multiple periods (table 1-2), namely Bosi period, Xuefeng period, Caledonian period, Hercynian period, Indosinian period, Yanshan period and Himalayan period.

(I) Bosian magmatic rocks

Table 1-2 Table of magmatic evolution and lithologic characteristics in different periods in Nanling area

Bosian magmatic rocks are scattered, mainly extrusive rocks and ultrabasic rocks, basic and intermediate-acid small rocks.

1. Volcanic rocks

It is mainly found in Rongshui County and Luocheng County of Guangxi, but also in northwest and northeast Jiangxi, Yiyang, Liling and Liuyang of Hunan.

The early eruption in Guangxi was the spilite-amphibole series of Bos Group [8], including spilite, amphibole, tuff, volcanic breccia and agglomerate. It occurs in the upper part of the ninth group of Yuangu Yusibao Group and Yuxi Group, with lava in the lower part and pyroclastic rocks in the upper two layers. Volcanic rocks in each layer are generally tens to hundreds of meters thick. It belongs to submarine eruption rock, mainly fissure eruption, with central eruption, multiple overflow or eruption in some areas. In the early stage, it was mainly overflow, forming the lower four layers of lava; Late eruption dominated, forming two layers of pyroclastic rocks.

There are basalt, andesite and keratophyre in Lengjiaxi Group, Hunan Province. The total thickness of volcanic rock series is greater than 1000m, and there are two eruption cycles [9].

The lower part of Mesoproterozoic Shuangqiao Group [10] in northwest Jiangxi and northeast Jiangxi is ultrabasic rocks and basic rocks, the middle part is calc-alkaline volcanic lava and pyroclastic rocks, and the upper part is turbidite sedimentary rocks composed of tuffaceous mud and fine debris. Lithology includes spilite, keratophyre, quartz keratophyre and metamorphic basalt. Layered, layered, lenticular and so on. Sandwiched in Shuangqiao Mountain Group, it belongs to submarine eruption.

2. intrusive rocks

After magma overflows or erupts, it invades.

In the early stage, there were ultrabasic rocks-basic intrusive rocks, which are a set of deep to shallow diagenetic assemblages mainly composed of metamorphic peridotite, pyroxenite and diabase, and are related to basic volcanic rocks. Except for a few rock bodies in the form of rock basins and caps, most of them are bedrock-like rock bodies. Most of the rock masses are concentrated in the Xibijiao Porphyry Formation of Wentong Formation and its underlying Jiuya Formation Complex. Danzhou Group is deposited on rock mass. Early intrusive rocks are mainly distributed in Jiuwandashan and Yuanbaoshan in northern Guangxi, with more than 500 intrusive rocks.

The late intermediate-acid intrusive rocks are medium-fine grained granodiorite and granodiorite porphyry, which are scattered in Dapoling and Rongshui of Luocheng. The total exposed area of rock mass is about 80km2. The rock mass intruded into Bos Group and early ultrabasic rock mass, and was covered by Danzhou Group. The age of granodiorite in this cave is 1422 ~ 1340 Ma, and the age of rubidium-strontium is 1063Ma.

(2) Xuefeng magmatic rocks

The distribution of magmatic rocks in Xuefeng period is wider than that in Bao Si period, which can be seen in five provinces (regions).

1. Volcanic rocks

Widely distributed, the five provinces (regions) have different degrees of development. Lithology includes spilite, olivine basalt, basalt, andesite, tuff, etc. And some places are bad. Mainly marine extrusive rocks, but there are also continental volcanic rocks.

Early Xuefeng volcanic rocks developed in Neoproterozoic. Volcanic rocks in Guangxi are distributed in the axis of Longsheng and Sanmen anticlines, linearly arranged in the northeast direction, with a length of several tens of kilometers and a width of about 20 kilometers respectively, and extend intermittently to the north in Hunan. Volcanic rocks occur in Danzhou Group and Series Formation, and consist of spilite, amphibole, tuff lava and volcanic breccia. After three eruption cycles, the first cycle is basic overflow; The activity of the second cycle is enhanced, which is accompanied by strong explosive activities in addition to widespread spillover. There are 1 ~ 7 eruption rhythms composed of volcanic breccia-spilite or spilite and amphibole; The third cycle is greatly weakened, characterized by intermittent overflow, including spilite and hornblende. There are andesite-dacite volcanic breccia in floor streams such as Yiyang and Longhui in Hunan Province, which are produced in irregular elliptical cones and belong to central eruption. There are also breccia glass-based basalt and basaltic lava. There are marine and continental volcanic rocks in the lower part of Neoproterozoic in Jiangxi Province. Marine volcanic rocks are mainly distributed in Hanzhai, Pingxiang-Yingshan Village, Geyang and other places. It is a spilite-quartz keratophyre belt, which occurs in the lower part of Shenshan Group and Shangye Group from east to west. Continental volcanic rocks are distributed in northwest Jiangxi, and consist of almond-shaped andesite basalt, andesite porphyrite, andesite, dacite, rhyolite and ignimbrite. , produced in the upper part of Shangye Group. The Luoke Group in Jiulingshan area of northern Jiangxi is a set of volcanic-continental clastic rock formations, which are superimposed in parallel on the uplift belt formed in the first act of Jinning (Bao Si) Movement along the "deep fault in northeastern Jiangxi". It is in false conformity or unconformity contact with the overlying Early Sinian Dongmen Formation and Tang Zhi Formation. Continental volcanic rocks erupt in fissure type and central type, and the latter is dominant.

Volcanic rocks in the late Xuefeng period occurred in the Lower Sinian. Volcanic rocks are controlled by NNE, NE and other structural zones. Yingyangguan area bordering Hunan, Guangxi and Guangdong is a set of metamorphic basic-intermediate acid submarine volcanic eruption rocks, which are distributed in a NE-trending belt, mainly composed of keratophyre and its corresponding pyroclastic rocks, with a small amount of spilite and quartz keratophyre. It can be divided into three eruption cycles, and each cycle consists of more than 2-5 eruption rhythms of volcanic breccia-tuff or volcanic breccia-lava, that is, intermittent eruption, which is characterized by weak magma overflow after strong eruption. Hunan Sinian volcanic activity is weak, and the exposed area is only about 2km2, all of which are basalts. However, volcanic activity in central and southern Jiangxi is strong, mostly submarine volcanic eruption, forming tholeiite and spilite porphyry formations. Wuyishan-Lushan area to the east of Ganjiang River is widely distributed, while Wugong Mountain, Jinggangshan Mountain and Zhuguang Mountain to the west of Ganjiang River are scattered. In Guangdong, except Yingyangguan area, the second subgroup of Sinian Yunkai Group in Xinyi-Luoding-Yunfu and Li Anping-Heping areas contains metamorphic volcanic rocks, including metamorphic basic volcanic rocks, metamorphic andesite, metamorphic acid tuff and rhyolite.

2. intrusive rocks

The distribution of intrusive rocks is smaller than that of volcanic rocks, mainly exposed in northern Guangxi and northern Jiangxi. There are Yuanbaoshan and Sanfang (Motianling) granitoids in northern Guangxi, and Jiuling complex in northern Jiangxi.

Jiuling complex is a compound complex dominated by granodiorite and granite. It intrudes along the axis of Jiuling compound anticline, forming nearly east-west bedrock with an exposed area of 2500km2 (Figure 1- 13). Granite intrusion can be divided into at least three stages. The first stage is cordierite rich in plagiogranite; The second stage is rich plagiogranite; The third stage is fine-grained biotite granite and mica granite. The rock mass invaded the Mesoproterozoic Shuangqiao Group and was covered by the Dongmen Formation of the Lower Sinian. K-Ar isotope age is 805Ma.

Yuanbaoshan and Sanfang (Motianling) granite bodies are located in the northeast of Xuefeng uplift structural belt, respectively, and are bedrock-shaped (Figure 1- 13), with a total exposed area of 1448km2. It is a composite rock mass, which can invade at least four times. The bedrock of medium-grained porphyritic biotite granite was formed by one intrusion, and gneiss porphyritic biotite granite was formed by dynamic metamorphism. The second intrusion formed the bedrock of medium-grained mica granite. The rock mass has obvious phase transition, and the marginal facies are fine-grained mica granite and mica granite porphyry, with massive pegmatite developed. The transition phase is unequal-grained mica granite, and the central phase is medium-grained mica granite. The third intrusion formed anisometric biotite granite, which invaded the gneissic porphyritic granite of the first intrusion. The fourth intrusion formed fine-grained mica granite containing tourmaline, mainly small rock mass in the form of rock plants or dikes. Rock intruded into Bos Group, Beijing No.3 Institute, Yichang Institute of Geology and Mineral Resources, Guiyang Institute of Geochemistry and other units. According to the isotopic age of uranium, lead and rubidium and strontium, it changed from 712 to 808 Ma, with a value of 760Ma, which was designated as the Xuefeng period.

(3) Caledonian magmatic rocks

It is widely distributed and can be seen in all provinces (regions) in Nanling (Figure 1- 14). Mainly intrusive rocks, volcanic activity is extremely weak.

1. Volcanic rocks

Caledonian volcanic rocks are only found in parts of Guangxi and Guangdong. In Guangxi, there are amphiboles in the lower Ordovician and spilite in the lower Silurian, only in Daming Mountain and Cenxi. There is a layer of metamorphic rhyolite in the metamorphic sand shale of Liantan Formation of Lower Silurian in Luoding, Guangdong, with a thickness of 6.49 ~ 25m [1 1]. Upper Silurian volcanic rocks in Mashan, Kaiping are rhyolite, dacite and andesite, which are dome-shaped and bell-shaped.

2. intrusive rocks

Intrusive rocks are very different from volcanic rocks, with wide distribution and strong activity, second only to Yanshanian intrusive rocks. Among them, the magmatic intrusion in Guangxi is the strongest, and the Caledonian magmatic intrusion in central and southern Jiangxi is also more frequent.

The Caledonian intrusive rocks are mainly granite, followed by migmatite and granodiorite, with a small amount of granite porphyry, granodiorite and quartz diorite. These rocks invaded the Lower Paleozoic, and some of them were covered by Middle Devonian sediments, and the isotopic age values obtained were 355 ~ 548 Ma, which can be used as evidence.

Granite bodies are widely exposed, which can be seen in all provinces and regions, and often form large-scale bedrock, some of which are rock plants. Especially at the junction of Guangxi and Hunan, such as Yuechengling, Miaoershan, baimashan and other granite foundations. Granites mainly include medium-grained porphyritic biotite granite, gneiss fine-grained porphyritic biotite granite, biotite adamellite granite and biotite granite. In gneiss granite, the gneiss direction is basically consistent with the regional tectonic direction.

The migmatite and mixed granite are mainly distributed in Wuyi-Yunkai uplift belt and its two sides, forming a north-south-north-northeast rock belt. These rocks include gneiss plagiogranite, gneiss biotite adamellite and plagiogranite.

Granodiorite is distributed sporadically, and there are small rock-like blocks in other areas except Daning rock mass at the border between Guangxi and Guangdong. Most of them are exposed at the intersection of NE or NE deep fault zone and east-west structural zone. Daning rock mass is a NW-trending bedrock dominated by granodiorite, but the edge of the rock mass often transits to quartz diorite (or Shi Ying adamellite). The rock mass intrudes into Sinian and Cambrian, and is covered by Guitou Formation of Middle Devonian.

(4) Hercynian magmatic rocks

Volcanic rocks are more widely distributed than intrusive rocks in Hercynian, and intrusive rocks are mainly small rocks, but generally speaking, the magmatic activity in Hercynian is not strong.

1. Volcanic rocks

Because the crust is in a relatively stable stage, the Hercynian volcanic eruption is also in a relatively weak state. Volcanic rocks are only found in Devonian, Carboniferous and Permian in parts of Guangxi, Guangdong and Fujian provinces. It is mainly intermittent submarine eruption and overflow, forming a set of volcanic rocks with many horizons, small thickness and medium basicity.

Devonian volcanic rocks. Western Guangxi, southern Guangxi and central Guangxi are a set of alkaline intermediate-basic submarine eruption rocks, mainly lava, followed by pyroclastic rocks. The lower part of the Lower Devonian Mo Ding Formation is basalt, which is distributed in Babu area of tianlin county. There are volcanic breccia, tuff lava, basaltic porphyry and coarse porphyry. Upper and middle parts of Donggangling Formation of Middle Devonian. The bottom and middle of Upper Devonian is located in the area from Wang Ban and Ba Du to Wude, Longzhou County, and occurs in the porous almond trachyte at the bottom of Rongxian Formation. Devonian volcanic rocks in Guangxi occur in the above five horizons, forming five eruption cycles. Rhyolite and rhyolitic tuff lava are distributed at the bottom of Dinghushan Group of Middle-Upper Devonian in Enping-Kaiping area, Guangdong Province. Upper Devonian volcanic rocks include tuff and tuffaceous sand shale of Shuangtou Group in Dongshi area of plain, and acid pyroclastic rocks and tuff in the upper part of Dawushi Formation in Jinji area of Kaiping. There are intermediate-basic volcanic rocks in Taozikeng Formation of Upper Devonian in Fujian.

Carboniferous volcanic rocks can only be seen sporadically in Guangxi and Fujian. There are early Carboniferous volcanic rocks in Jingxi, Guangxi, which are scattered in the middle and lower parts of the Yan 'an Stage, including basalt, breccia lava and tuff. Guangdong, on the other hand, is a middle-late Carboniferous Hutian Group with volcanic rocks, and pyroxene andesite, andesite, potash feldspar felsic, rhyolite, andesite tuff and pyroclastic rocks can be seen at the top of Li Anping.

Permian volcanic rocks can be seen locally. Early Permian volcanic rocks of Tongziyan Formation are found in Xingning, Heyuan and Ang Lee in eastern Guangdong Province, and occur in interlayer coal measures strata. They are mainly andesite and neutral tuff containing volcanic breccia and acid tuff. Late Permian volcanic rocks with a thickness of 0.5 ~ 3m are only exposed in some areas of Jiubeishitang and Li Antang in Lianxian County, Guangdong Province, Huashan in Guangzhou suburb, Longlin, Chongzuo-Ningming, Qinzhou and Liuzhou, and are basalt. These volcanic rocks are thin in thickness and poor in continuity, showing the characteristics of eruption first and then overflow.

2. intrusive rocks

Hercynian intrusive rocks have almost no stratigraphic basis, and their ages are mainly determined by age data. According to the current1:500,000 geological map of the region and the regional geological records of various provinces, there are diorite, granodiorite and granite. These rock bodies are distributed in northern Guangdong, western Guangxi, Fujian Pu, Zhenfengding, Jiangxi Gaojiatian, Maixie and other places. Rock mass occurs in the form of bedrock, rock plant or dike.

Both the Piaotang depression in Renhua, Guangdong Province and the upper Long Yun gabbro in Nanxiong intruded into the Middle Devonian. They were invaded by Indosinian ophiolite adamellite and Yanshanian granite. Zircon and amphibole ages measured from Yunhui monzonite are 365, 438+065, 438+0 Ma and 240Ma respectively.

Granite bodies distributed in Xiaju, Zhenfengfeng, Liu Qing, Liancheng, Bao Si, Xiping, Longxi and Mianhuawo, Nanxiong, Guangdong, have not yet obtained the data of intrusion relationship. Pu Ru pluton intruded into upper Devonian quartzite and was covered by lower Cretaceous. According to its time data (196 ~ 273 Ma), it is tentatively called Hercynian period.

(5) Indosinian magmatic rocks

During this period, magmatic activities developed locally and distributed sporadically.

1. Volcanic rocks

The activity is weak, mainly developed in parts of Guangxi, Guangdong and Fujian.

Early Triassic basic-intermediate acid volcanic rocks. Napo area in Guangxi is a set of basic volcanic rocks, which consists of spilite, tuff breccia and breccia lava, and occurs in the middle and upper parts of Luolou Group in layers. Pingxiang area is a set of intermediate-acid volcanic rocks, which consists of breccia lava, intermediate-acid lava and tuff lava. There is a layer of vitrinite tuff with a thickness of 65438±0.5m in the Lower Triassic Daye Formation in Jiubeishitang, Lian County, Guangdong Province.

The Baifeng Formation in western Guangxi, central Guangxi and southwest Guangxi produces acidic and intermediate-acidic volcanic rocks in the Middle Triassic, and there is still acidic tuff in the middle of Hekou Formation in Baihe area of Napo County. There is a set of quartz porphyry (possibly subvolcanic rocks) under the volcanic rocks in Naguanshan area.

The Lower and Middle Triassic is marine deposit, and volcanic rocks are submarine eruption or overflow.

The late Triassic Banba Formation in Guangxi consists of rhyolite porphyry, perlite, tuff lava and fused tuff, which belongs to continental eruption. The Jiaokeng Formation and Wenbinshan Formation in northern and southwestern Fujian produce late Triassic andesite and andesite tuff lava, with occasional pyroclastic rocks such as rhyolite and tuff. Wenbinshan Formation is lacustrine deposit, Jiaokeng Formation is inland intermontane basin deposit, and volcanic rocks are continental eruption.

According to the development history of volcanic activity and crustal movement in the two regions, the early and middle Indosinian period was submarine eruption and later became continental eruption.

2. intrusive rocks

At present, reliable stratigraphic basis is only found in acidic-intermediate acidic intrusive rocks in southeastern Guangxi, and intrusive rocks in other areas are mainly determined by isotopic age. The acid intrusive rocks in southeast Guangxi, represented by Darongshan granite, can be divided into two sub-periods. The first sub-stage is mixed granite as bedrock, which is divided into four intrusions. The first time is cordierite biotite granite, which generally has strong assimilation and contamination, and is produced as a huge bedrock with an exposed area of 6450km2. The phase transition is obvious, the marginal phase is narrow, sometimes there are granite porphyries, and the transitional phase is developed. Invasion in Paleozoic strata, extensive keratinization zone. The second intrusive rocks are mostly distributed in the northwest of Darongshan rock mass or intruded into it, and the lithology is garnet biotite granite, cordierite perilla granite porphyry, cordierite biotite granodiorite, cordierite biotite plagiogranite, etc. The third intrusive rock is a small rock mass, mainly composed of perilla granite porphyry, with obvious contamination and many xenoliths. This time, Matai rock mass intruded into the Dasi rock mass invaded for the second time. The fourth intrusive rock is a small rock mass, the stable rock mass is composed of biotite perilla granite, and the other rock mass Dongna rock mass occurs in northeast belt. It is mainly composed of biotite granite in Wen Xiang. This rock mass intruded into the third Matai rock mass. The rocks invaded from the first time to the third time were all covered by the sediments of the Lower Jurassic. The latest stratum of Darongshan intrusion for the first time is Upper Permian, but the isotopic age is mostly between 238 and 289 Ma, which is on the high side. Yichang Institute of Geology and Mineral Resources and Guiyang Institute of Geochemistry believe that it belongs to Hercynian period. Matai intrusive body intruded into Lower Triassic for the third time and was covered by sediments of Upper Triassic and Lower Jurassic (Figure 1- 16), that is, it invaded in Indosinian after Early Triassic and before Late Triassic, but the zircon age was 285Ma, which was inconsistent with geological phenomena. In addition, the mineral composition and chemical composition of Matai rock mass are similar to those of Darongshan rock mass invaded for the first time and the second time (Table 1-3), and they all have characteristic minerals such as cordierite and garnet, which should be the product of the intrusion of homologous magma at different stages in the same period. In particular, the composition of these intrusive rocks (Table 1-3) is similar to that of Triassic volcanic rocks (Table 1-4), but it is quite different from that of late Triassic volcanic rocks dominated by basalt, so it is considered that Triassic volcanic rocks and Darongshan intrusive rocks are the products of simultaneous homologous magma evolution. According to the above factors and intrusion relationship, it is determined that the Darongshan rock body is an Indosinian intrusive body.

Figure 1- 16 Indosinian Matai rock mass covered by Upper Triassic sediments

(Beside the l00m River in the west corner of Guangxi Bureau of Geology and Mineral Resources)

Indosinian rock mass (): 1- perilla granite porphyry; 2- Antique Perilla Granite. Upper Triassic (T3):3- granitic conglomerate; 4- feldspar siltstone; 5- Coarse grained sandstone in cuttings; 6— Fine-medium grained feldspathic sandstone; 7— Silty mudstone

In the second sub-stage, intrusive rocks mostly exist in the form of rock plants, which are distributed in southeast and northeast Guangxi, mainly including Niumiao, Du Nan and Xishan. The lithology is complex. In addition to biotite granite, there are granodiorite, syenite and quartz monzonite, most of which invaded the late Paleozoic strata and were covered by Cretaceous, so the basis for age division is insufficient. In addition, there are basic and ultrabasic intrusive rocks such as diabase, gabbro, peridotite-gabbro, and the latest intrusive stratum is Lower Triassic.

(6) Yanshanian magmatic rocks

The Yanshanian magmatic rocks in Nanling area are the most widely distributed and have frequent and intense activities, which is the heyday of magmatic activities in this area. Mainly intrusive rocks, but volcanic rocks are also well developed. Among them, the late Jurassic magmatic eruption and intrusion activities were the strongest and most widely distributed, and Nanling distributed from east to west.

1. Volcanic rocks

The Yanshanian magmatic eruption was unprecedented. Intermittent eruption began in the early Jurassic and reached its peak in the late Jurassic. Its scale and intensity greatly weakened in the early Cretaceous, and basically ended in the late Cretaceous.

(1) Early Jurassic volcanic rocks

Widely distributed, but sporadic, that is, local areas in various provinces and regions are developed. Acid volcanic rocks in Liangjiangkou, Hunan, basic volcanic rocks in Hengshan, Rucheng and Beixi in eastern Guangxi, andesite in Laomengshan, Changning, and intermediate-acid volcanic rocks in Yueliang Village, Guiyang. Guangxi is only found in the western margin of Liu Ma Basin in Beiliu County. The top and bottom of the Lower Jurassic are tuff clastic rocks and tuff, and the middle part is volcanic breccia or intermediate acid tuff. Early Jurassic volcanic rocks in Guangdong are exposed in Jiaoling-Meixian-Dabu area in northeast Guangdong. Huiyang-Heyuan in central Guangdong and Yangchun in western Guangdong. It can be divided into two types: the volcanic eruption subcycle of the Lower Jinji Formation and the volcanic eruption subcycle of the Upper Qiao Yuan Formation. Jinji Formation is a set of basic-intermediate acid volcanic rocks with strong volcanic activity in shallow sea. Qiao Yuan Formation is composed of clastic rocks mixed with acidic volcanic rocks, alternating between land and sea, with weak volcanic activity (Figure 1- 17).

Table 1-3 Petrochemical Composition Table of Indosinian Granite (wB/%)

According to the regional geological records of Guangxi.

Table 1-4 petrochemical composition (wB/%) and numerical characteristics of Triassic volcanic rocks

According to the regional geological records of Guangxi.

Figure 1- 17 eruption rhythm of early Jurassic volcanic rocks in eastern Guangdong

(According to the regional geology of Guangdong Province)

J3GJ-Upper Jurassic Gaojiping Group; J 1q—— Lower Jurassic Qiaoyuan Formation; J 1j—— Lower Jurassic Jinjiling Formation; T3gn—— Upper Triassic Genkou Formation

(2) Middle Jurassic volcanic rocks

The distribution range is narrow, and it is distributed locally, mainly in parts of Guangdong, Jiangxi and Fujian. There are volcanic rocks of Zhangping Formation and Maziping Group in the Middle Jurassic in Guangdong. Zhangping Formation consists of continental pyroclastic rocks and lava interlayers, which are mainly exposed in Shenzhou, Huiyang and Huidong in central Guangdong, and Li Anping, Meixian and Dabu in northeastern Guangdong, among which Meixian-Dabu area is the most developed and distributed in northeast belt. The volcanic rocks of Maziping Group are exposed in Maziping and Renhua Huangkeng in Qujiang, northern Guangdong.

(3) Late Jurassic volcanic rocks

Late Jurassic is the peak of volcanic activity, and the activity east of Nanling is the strongest. It is mainly controlled by NNE or NE-trending faults, and erupts at the crack or crack center, forming an NNE or NE-trending volcanic belt.

The late Jurassic volcanic activity was particularly strong in the eastern coastal areas of Nanling, that is, eastern Fujian and eastern Guangdong, and volcanic rocks were distributed all over the region. The lithology has obvious eruption cycle of intermediate-acid magmatic evolution. The Upper Jurassic in Fujian is almost entirely composed of volcanic rocks, and the sandstone of Changlin Formation at the bottom is sandwiched with andesite and tuff, forming a magmatic evolution series. The central part of Nanyuan Formation is dominated by volcanic rocks, sandstones and shales, which can be divided into four lithologic sections from bottom to top. The first section is mainly andesite, dacite mixed with volcanic breccia, agglomerate and a small amount of rhyolitic crystalline tuff lava. The second section is rhyolitic microcrystalline lava, rhyolite, tuff and ignimbrite. , sand shale. The third section is dacite, dacite tuff, rhyolite dacite tuff lava and ignimbrite, which often transits with intermediate-acid porphyry lava and is mixed with thin layers of sand and mudstone. The fourth section is rhyolitic crystalline tuff, tuffaceous lava, rhyolitic ignimbrite, gabbro rhyolite, rhyolite mixed with tuffaceous siltstone, sand shale, siliceous rock and pea-shaped tuff. Two semi-magmatic evolution and eruption cycles from neutral to acidic and intermediate acidic were formed. The Xiaoxi Formation in the upper part of Upper Jurassic is dominated by acidic volcanic rocks: rhyolitic crystalline tuff, ignimbrite, stone bubble rhyolite, etc. The eastern Fujian volcanic belt, like the eastern Guangdong volcanic belt, extends to the south and west, and also develops along the NE-NE fault zone, forming a 500-600 km long NE-to-East volcanic belt in eastern Guangdong. Among them, Lianhua Mountain Belt and Nan 'ao-Chaoan Belt are the largest. Late Jurassic volcanic rocks are produced in Gaojiping Group, which is a set of continental and continental lacustrine andesite-dacite-rhyolite formations, forming a set of thick neutral-intermediate acid lava, corresponding pyroclastic rocks and a small amount of sedimentary rocks. It can be divided into four eruption sub-cycles: the first sub-cycle is andesite clastic rock mixed with neutral volcanic rock; The second sub-cycle is composed of neutral volcanic rocks, with sedimentary layers and iron ore layers; The third cycle is acid volcanic mixed sedimentary rocks (Figure1-18); The fourth sub-cycle is intermediate-acid and acidic volcanic rocks mixed with sedimentary rocks and iron ore beds (Figure 1- 19). Among them, the third eruption sub-cycle is the most developed, with sporadic outcrops not only in eastern Guangdong, but also in the whole province, while the first and second eruption sub-cycles are only distributed in the west of Lianhuashan fault zone, and the fourth eruption sub-cycle is only distributed in the east of Lianhuashan deep fault zone. Therefore, in time and space, the western horizon is low, the eastern horizon is complete, and it changes gradually from west to east from old to new.

Late Jurassic volcanic rocks are distributed in the middle of Nanling, northeastern Jiangxi, southern Jiangxi, central Guangdong and western Guangdong, and mainly gush out along the NNE deep fault zone, east-west and other structural intersections. There are several NE-trending volcanic belts in Heyuan-Xunwu, Xinfeng-Li Anping-Longnan, Wuchuan-Sihui and Yunan-Lianxian, and volcanic rocks are exposed sporadically along these belts. Lithologic assemblage and rock types are complex and diverse, and all belong to basalt-andesite-dacite of calc-alkaline volcanic rock series, which can be generally divided into 2 ~ 4 eruption cycles.

Late Jurassic volcanic rocks have not been found in the west of Nanling.

Late Jurassic volcanic activity and subvolcanic complex activity occurred simultaneously or later. A subvolcanic rock with a gradual relationship with erupting volcanic rocks, whose lithology includes dacite porphyry, syenite porphyry, andesite porphyry, quartz porphyry, granite porphyry and syenite porphyry; The other is ultrahypabyssal-hypabyssal intrusions, all of which have the characteristics of cryptoexplosion. There are not only cryptoexplosive breccias cemented by magma, but also volcanic or subvolcanic veins in the cracks around them.

(4) Cretaceous volcanic rocks

Now it is the late Yanshanian eruption, which is coming to an end, and there are few large-scale volcanic magma eruptions. Magma often erupts and invades along several groups of structural intersections, especially the NNE deep fault zone that runs through the crust and the east-west structural intersection, with the central eruption as the main one. These volcanic institutions are arranged along the NNE or NEE, and are distributed in beads (Figure 1- 15). It is divided into several NE-trending rock belts from west to east, mainly including: scattered basalt belts in the NE-trending structural belt from Huilongxu, Jiangyong, Hunan to Xilou, Liuyang; Middle-acid volcanic rocks in Bobai-Cenxi northeast secondary deep fault zone of Yunkai northeast deep fault zone; And the acidic volcanic rocks in the northeast deep fault zone of Lianhua Mountain.

2. intrusive rocks

Yanshanian intrusive rocks are the most widely distributed and the largest in scale. Like volcanic rocks, their activity intensity and breadth are unprecedented, and they are in their heyday. Rock types are complex and vary greatly. Ultra-basic rocks, basic rocks, intermediate rock, acid rocks and alkaline rocks are exposed, and granite is absolutely dominant.

Yanshanian intrusive rocks are the product of multi-stage and multi-stage intrusions, which can be divided into early and late stages.

Early intrusive rocks can be divided into three stages: the first stage intrusive rocks, mainly granite, followed by basic-ultrabasic rocks. Rock mass is mostly produced by rock foundation and rock plants; The intrusive rocks in the second stage are mainly granite, followed by basic rocks. The intrusive rocks in the third stage are mainly granite, followed by basic, neutral and alkaline rocks. At this stage, the intrusion strength and scale of granite slurry reached the peak. Most of them form a huge granite foundation, and some of them are produced as rock plants and rock walls.

Figure 1- 18 Rhythm diagram of the first, second and third lithologic members of the volcanic rock series of Gaojiping Group in Conghua and Meixian areas.

Late Jurassic volcanic rock series: the third lithologic member (J3G JC); The second lithologic member (J3GJB); The first lithologic member (J3GJA); Lower Jurassic (J 1)

The intrusive rocks in the late Yanshan period are mainly granite, followed by basic-ultrabasic rocks, neutral and alkaline rocks.

(7) Himalayan magmatic rocks

Magmatic activity is not only weak, limited in distribution and small in scale, but also mainly the overflow and eruption of basic magma and the eruption of acidic magma dominated by rhyolite. Magma overflows and then invades.

1. Volcanic rocks

It is distributed in some areas in the southeast of Nanling, mainly including Zhangpu Buddhist altar in Fujian, Xuefeng in Mingxi in Pingnan, Xiacun, Heyuan, Sanshui and Li Anping in Guangdong, and Xinxu in Hepu, Guangxi. The ejecta are mainly olivine basalt, followed by andesite, trachyte and rhyolite, with pyroclastic rocks in the middle. Generally, it occurred in Tertiary, and some occurred in Quaternary Pleistocene or Holocene. Spillover activity has the characteristics of multiple cycles, generally 2 ~ 4 cycles. The trachyte in Zoumaying, Sanshui, Guangdong is 47Ma, and the basalt in Xiaotang, Sanshui is 64Ma.

Figure 1- 19 Rhythm Diagram of the Third and Fourth Lithologic Members of the Volcanic Rock Series of Gaojiping Group in Late Jurassic in Lianhuashan Area

Late Jurassic volcanic rock series: the fourth lithologic member (J3GJD); The third lithologic member (J3G JC); Lower Jurassic (J 1)

2. intrusive rocks

Scattered in parts of Fujian, Guangdong, Guangxi and Jiangxi. It is produced by rock plants and dikes (walls). Gabbro is dominant, followed by gabbro and gabbro (porphyrite); In Bai Han, Nanfeng County, Jiangxi Province, there are two granite bodies, Ou Long and Guojiashan, which are fine-grained and medium-grained biotite granites, invading the tertiary Xinyu Group with an age of 37Ma.

Most rocks intrude into Upper Cretaceous or Tertiary.