Abstract:Linglong granitic complex is a compound rock body characterized by long evolutionary history and multiple reformation and remelting, with Guojiadian type and Guojialing type rock bodies being of Early Yanshanian and Late Yanshanian respectively. Inversion of 16 gravity and magnetic profiles shows that Linglong granitic complex is a rock body in the form of winnowing pan, with Guojiadian as the remelting center. It assumes low angle overlap northward and high angle contact with wall rocks southward, and over 86% gold deposits occur in places with the rock body thickness less than 4km. Different positions of Linglong granitic complex have different source rock compositions. According to spatial forms, source rocks and tectonic frameworks of the rock body, the Linglong granitic complex was divided into different rock areas with different rock forming and ore forming characteristics. The mathematic modeling of the formation of Linglong granitic complex revealed that in the remelting process, the enrichment of gold in fluid facies and the circulation of fluids driven by heat of the rock body constituted the basic factors responsible for the development of gold mineralization.

Abstract:The subduction-accretionary complex/volcanic arcs in the middle sector of North Qilian may be subdivided into subduction-accretionary complex zone and the volcanic arc zone. The former mainly comprises the Early Ordovician ophiolites, ophiolitic melanges and deep-marine flysch with features of ocean crust, within which the Middle to Late Cambrian volcanic rocks and clastic rocks characterized by continental rifting and continent-ocean transitional environment occur as lenticular blocks.Isotopic data show that the deep unit of the subduction-accretionary complex experiencedHP/LTmetamorphism during the period of 489—450Ma and the age of volcanic arcs is 495—466Ma, and that these geological bodies were formed as a result of northward subduction of Paleozoic Qilian oceanic crust beneath the Alxa blocks during the Early to Middle Ordovician.

Abstract:Mesozoic granitoids in the middle and lower reaches of the Yangtze River were formed in the process of adjustment of lithospheric matters after the collision of North China and Yangtze craton. Systematic studies of Sr, Nd, Pb isotopic data show that the two stages of granitoids are characterized by similar magmatic sources and the existence of crust crust mixing. In the crust crust mixed magmatic sources, the main mixing members may be the source rocks of the granitoids in DL and YZL lithozones, the former equal to high grade metamorphic rocks in Dabie complex and the latter being the basic and intermediate basic meta igneous rocks which underplated and midplated into the lower crust during Pt2-3 and the Pt1 sedimentary volcanic rocks in the Yangtze cratonr. Those characteristics indicate that the lower crust in the middle and lower reaches of the Yangtze River was tectonic melange belt between Dabie block and Yangtze block during the Mesozoic collision of the two blocks. Two different substances formed finger like connection texture in the lower crust of YZC block (the middle and lower reaches of the Yangtze River).

Abstract:Kunyushan granite distributed in Muping-Rushan area of Jiaodong is a multiphasic gnessic complex intrusion. It is composed of Duoguding gneissic granodiorite (147 Ma), Bamenzhoujia gneissic porphyritic granodiorite (135 Ma), Washan-Shuidao monzonitic granite and Wuzhaoshan gneissic garnetiferous monzonitic granite (120 Ma), and is geochemically characterized by poor aluminium and rich alkali. According to our work, it was emplaced mainly in Jurassic and, instead of being formed by metasomatism, was formed by condensated crystallization from magma derived from melting of Proterozoic intermediate acid metamorphosed volcanic rocks situated in the lower middle crust or the upper part of the lower crust, as a result of sudden decrease in pressure and temperature in the pliable lower crust. The granite was formed by crystallization and later it underwent plastic and brittle deformation. The different directions of gneissosity of the intrusion resulted from plastic deformation of melt as a result of different directions of stress. Faults and shatter zones formed by brittle deformation constitute the main passageways and host structures. There is a close relation between the emplacement and deformation of granite and the ore forming process of the gold deposits. In the process of brittle deformation of the intrusion, the silica rich hydrothermal solution crystallized and the recrystallization of quartz provided the carrier (quartz veins) for the concentration of mineralized materials. The main ore forming solution was the mixture of deep source auriferous hydrothermal solution and heated circulated groundwater. It extracted gold from metamorphic rocks, granite and lamprophyre, and caused its mobilization, migration and enrichment to form gold orebodies.

Abstract:The Quaternary basalts in Shandong Province contain mantle xenoliths of varied quantities and sizes. These mantle xenoliths are mainly spinel lherzolite characterized by protogranular and porphyroclastic textures.The dislocation substructures of olivine from the xenoliths indicate a deformation process dominated by dislocation creep under the upper mantle condition. The equilibration temperature and pressure of the xenoliths are estimated to be 800—1100℃and this range of depth, the differential stress of the upper mantle should be 13—26 MPa, while the strain rate and the equivalent viscocity are 10-14—10-20s-1, and 1020—1025Pa·s respectively. The thermal structure and rheological features of the upper mantle beneath the studied area coincide with those beneath the continental extension zone and the rift. It is considered that an upper mantle diapir occurred since Early Tertiary in eastern China, giving rise to the thinning of the lithosphere and the formation of extensional environment in this area. It reached its climax in Late Tertiary and has begun weakening since Quaternary.

Abstract:The studied copper(molybdenum) deposits include the Anjishan copper deposit and the Tongshan copper-molybdenum deposit, of which the former lies in the inflexion section of Nanjing-Zhenjiang Mountain arcuate structure, and the latter lies in the middle part of the same mountain chain. Both are medium-size ones. Associated with granodiorite porphyry and quartz diorite porphyrite, the Anjishan copper deposit is mainly of porphyry and skarn type. The single mineral (biotite and hornblende) K-Ar isotope ages of Anjishan rock bodies are between 123.1×106a and 106.0×106a,and K-Ar isochron dating gives an age of 123.0×106a. The Tongshan copper-molybdenum deposit is mainly of skarn type associated with quartz diorite porphyrite, whose K-Ar isotope age is 117.0×106a. Two pure molybdenite samples were collected from fine-grained disseminated ores of Anjishan and Tongshan deposits, with the former determined as 2H1+3Rpolytype and the latter as 2H1by means of XRD analysis. 187Re and187Os contents of molybdenite from the two deposits are determined by Inductively Couple Plasma Mass Spectrometry (ICP-MS), with Re-Os ages calculated by using the formulaλ (187Re)=1.64×10-11a-1. The results are 108×106a for the Anjishan deposit and 106×106a for the Tongshan deposit, which are both younger than the ages of the associated magmatic rock bodies, with the differences being 15×106a (Anjishan) and 11×106a (Tongshan) respectively.

Abstract:This paper studies characteristics of geological modes of occurrence, petrography and mineralogy of tourmaline bearing rocks as well as mineral chemistry of tourmaline, and deals with the genesis of tourmaline. Four modes of occurrence of tourmaline are recognized: (1) tourmaline accompanied with Beiyu granodiorite and granite porphyry, (2) veinlike tourmaline bearing rocks in metamorphic strata, (3) striped tournaline bearing rocks, and (4) tourmaline veins in the host rocks. The main mineral chemical characteristics of tourmaline are as follows: (1) the contents of FeO and MgO vary considerably, and there are four types of mineral species: Fe tourmaline, Fe rich tourmaline, Mg Fe tourmaline and dravite;(2) the relative variations of Al 2O 3, FeO, MgO contents are closely associated with types of host rocks and geneses of tourmaline;(3) Na 2O, Al 2O 3 and FeO, TiO 2 contents of tourmaline assume growth and decline relationship in granite porphyry and granodiorite, which corresponds with the mutual compensational relation of chemical composition of the host rocks. There exist three genetic types of tourmaline: (1) tourmaline formed by post magmatic hydrothermal solution at the late stage of Beiyu granitoid plutonism , including striped tourmaline bearing rocks;(2)tourmaline formed by metamorphic fluids in Zhongtiao Group; (3) tourmaline formed by hydrothermal alteration at the stage of copper mineralization and occurring in the host rocks and the near ore rocks. The third type of tourmaline is characterized by veinlet form, fine grain size, rich MgO and poor FeO and mineral assemblage of quartz, calcite, biotite, pyrite and chalcopyrite. All these characteristics constitute important ore prospecting indicators.

Abstract:Being the most important geothermal area with active hydrothermal manifestations in China,Tengchong is world-famous for its geothermal resources. Tectonically, Tengchong is located close to the junction zone of the Eurasian plate and the Indian plate. The residual magma gradually cooled down and became an ideal heat source for its overlying hot spring system. It is inferred from the thermometry of geyserite and adarce inclusions that underground temperatures for the hot spring system in Tengchong are 157—270℃. Surface hydrothermal alterations are well developed in the Tengchong active hot spring system. Tengchong has a great variety of special surface geothermal manifestations, such as warm springs, hot springs, boiling springs, sinters (geyserite, travertine, efflorescenceetc.), hydrothermal explosive breccias, and hydrothermal altered rocks, which are surface manifestations of geothermal activity in the interior of the earth’s crust. In this paper, mineral composition and chemical composition of geyserite in the Tengchong active hot spring system of Yunnan Province were studied by means of analytical electron microscopy (AEM) including transmission electron microscopy (TEM) and energy dispersive X-ray spectra (EDS),scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared absorption spectra (IR), chemical analysis and optical examination. The results indicate that geyserite consists mainly of amorphous silica (silica gel), opal, chalcedony and quartz, and that silica gel is composed of micron-sized (0.2—2μm) SiO2spherulites. Silica gel has played an important role in the enrichment of gold. Geyserite is only present in a few high-temperature hot water areas, such as the Hot Sea and Ruidia. It is found that the hot spring system contains abundant gold mineralization. Quartz veins and geyserite have remarkably high gold abundance: 0.198 ppm for quartz veins and 0.155 ppm for geyserite (the highest value being 0.39 g/t). The enrichment of gold in geyserite provides an important inspiration for the prospecting of hot spring gold deposits. Hence, Tengchong is a very promising area for ore prospecting. Geyserite may serve as an excellent ore-prospecting indicator and has important geological implications.

Abstract:Based on a systematic summary of research results available on typomorphic characteristics of zircon crystal form, this paper makes an approach to crystal growth mechanism of typomorphic characteristics of zircon with the help of theories of crystal growth, crystal chemistry and geochemistry. The results show that there exist differences in composition and proportions of atoms, links, power of chemical bonds, intervals and densities of crystal lattice faces in different directions of its crystal structure. These differences affect growth velocity of crystal lattice faces in different directions and control corresponding crystal forms under different conditions of crystalline media. For example, alkaline elements can affect diffusion velocity of Zr, Si and O ions although these alkaline elements cannot exist in crystal structure of zircon. However, K rich media and Na rich media exert different effects on the growth of crystal form: in the K rich media, growth speed of prism faces in the vertical direction is much higher than that of pyramid faces, and {111} growth speed in the vertical direction is higher than {311},which decides the formation of bipyramids dominated by {311} pyramids; in the Na rich media, both prism and pyramid grow to a certain extent, but the former is smaller than the latter. {100} growth speed in the vertical direction is lower than {110}, while {111} growth velocity in the vertical diredtion is lower than that of {311},resulting in the growth of the crystal form characterized by {100} short prism and {111} pyramid. With similar research method, this paper has proved the objective nature of the typomorphic characteristics of zircon, brought to light the internal and innate relations among typomorphic characteristics of zircon, and opened up the prospects of applying these characteristics to granite study, thus providing more analytical and applying value to single zircon grain geochronometry.

Abstract:There exists much controversy concerning the genesis of myrmekite, and most geologists hold that myrmekite is of metasomatic origin. Myrmekite occurs invariably in granulite facies metamorphic rocksand corresponding migmatitesand isoften found among plagioclase , orthoclase and quartz; the index of refraction of myrmekite-bearing plagioclase is lower than that of plagioclase without myrmekite. Based on these facts and taking into account the achievements obtained in recent experimental research on melting of granite rocks, the author considers that myrmekite is eventually formed by eutectic crystallization in the process of cooling and crystallization after granitic melts are formed through anatexis under the condition of granulite facies metamorphism.