Abstract:Cenozoic allkaline basalts in Northeast China contain abundant upper mantle- derived ultramafic nodules.According to the pressure and depth of the formation of the ultramafic nodules estimated by geobarometric method, the depth of generation of the basaltic and pyroxenitic magmas and geophysical data, a preliminary compositional model of the upper mantle beneath Northeast Chiria has been established. If the overlying crust-mantle transition zone above the Moho is included, five layers have been recognized as follows:l)the crust-mantle transition zone (28-35km)，2) the spinel 1herzolite layer (35-120 km)，3 the low-velocity zone containing trace amount of silicate melt from 60 to 120km; 4) the spinet harzburgite layer (120-200 km);5) the garnet peridotite layer (>200km).An oceanic geotherm for the upper mantle beneath Northeast China has been deduced from the calculated result by geothermometry. Compared with the typical craton geotherm, the low-velocity zone is at higher level and the oceanic geotherm nature indicate a condition for the upper mantle beneath Northeast China is "overheat". We suggest this is an interior cause of the continental rift generation in Cenozoic Era. Understandingthe composition, structure and thermal condition much better constrain the geophysical and petrological model of the upper mantle.

Abstract:The Qianlishan granite, which emplaced in the Sinian and Middle-Upper De- vonian eystems at the early stage of the Yanshanian movement (172-141Ma)， is a composite instrusive body. In instrusive sequence, it consists of fine-rainec porphyritic biotite monzonitic granite γ5(2-1)，medium to coarse-grained biotite monzonitic granite γ5(2-2)，fine-grained biotite monzonitic granite γ5(2-3)and granite porphyry (γπ). The Qianlishan granite is of magmatic origin. It has high SiO2 and relati- vely high A1 contents;Na2O/K20=0.5-0.9; 87Sr/86Sr=0.7328 and δ18O=+ 10.8%0 . The REE distribution pattern is of Eu-depleted type with intensive negative Eu- anomaly. Therefore, this intrusive body belongs to S-type granite. Based on the characteristics of its emplacement, the source rocks of the Qxanlisha.n granite might be Pre-Sinian sediments. From γ5(2-1) through γ5(2-2) to γ5(2-3) the evolution of magma shows obvious trend, i. e., the differentiation index (DI)，alkalinity, the IiREE content. anti they degree of Eu depletion become higher and higher; the contents of granitophile increase, whereas those of granitophobe elements decrease, but the granites of πγ doesn't follow these trends. Based on the above, it is thought that γ5(2-1),γ5(2-2) and γ5(2-3) are aslated to comagmatic fractional differentiation but γπ is not. Ju-dging from its mode of occurrence granites γπ probably came from a level dee-per than the others in origin.

Abstract:The Lengshui volcano-intrusive complex occurs in the Mesozoic volcanic depression of the northeastern Jiangxi province. Its country rocks are mainly metamorphic rocks of Banxi Group. This complex consists of extrusive rocks which are mainly rhyolite-pyroclastic rocks, different kind of subvolcanic rocks and shallow-plutonic rocks from the basic basalt-porphyrite to the acidic granite-porphry. It belongs to a calcalkalie rock series, but it exhibits some features of the potash-rich subalkalic rocks formed at the late stage of the magmatic differentiation. The regularity in the development of the zoned magma chamber can be seen in the perfect fractional crystallization, gravitational differentiation and intrusive sequence. The Rb/Sr and Li/Mg ratios of the rocks increase, while the Ba/Rb ratio decrease with the evolution of the petrochemical composition from basic to acidic. The content of siderophile elements is quite low and that of chalcophile elements is high in the complex in comparison with the same kind of rocks in South China. The REE distribution patterns of the rocks show similarity with the syntectic granitoid in South China. The initial ratio of (87)Sr/(86)Sr is 0.7139. The rock-forming materials originated mainly from partical melting of lower crust of the earth. The authors have concluded that the volcano-intrusive complex is comagmatic rock and it is resulted from the different evolvementary stage of the s yntectic magma.

Abstract:Some small isolated masses of ultramafic lavas have been found in the Upper Pillow Lava of the Troodos ophiolite complex, Cyprus. The ultramafic outcrops described here occur some 13 miles to the south-west of Nicosia, near the village of Margi. Two samples (79-4-2 and 79-4-4) were collected from this area in 1979. In this paper an account is given of their petrography, mineralogy and chemistry. We wish to emphasize some of these rocks are analogues of komatiitic basalts. Our study, although preliminary, shows that there is a remarkable similarity in texture, mineralogy, marjor element and trace element composition of the rocks for comparison with komatiitic basalts.

Abstract:Based on large amounts of data, this paper makes an analysis of the petrochemistry, ngnferrous metals, trace-element and the REE distribution of the granites in Pingquan district of Xinglong. This study deals mainly with the geochemical characteristics of two types of rocks related to minerahzation in this district, i. e., granite-granite porphyry and granodiorite. The paper points out that the geochemical difference between these two types of rocks is mainly related to the origin of their rockforming materials, beside their different petrological characters.

Abstract:Petrogenetic grids of greenschist facies of metavolcanic and metavolcani- elastic rocks can be fundamentally represented by an assemblage of six phases of ternary system:. actinolite-biotite-calcite-chlorite-epidote-muscovite; and an- other assemblage of six phases of ternary system; albite-actinolite-biotite-calcite -chlorite-epidote, Generally quartz is an excess component. On the premise that the petrogenetic grids discussed possess dual similar intepsity variables. each assemblage of the six phases of ternary system has only a pair of petrogenetic grids. But the non-closed divariant fields of that pair of petrogenetic grids are similar. The slopes of boundaries (corresponding univariant curves) between non-closed divariant fields of the pair of petrogene- tic grids are of the same too. Also the arranged sequence of the non-closed divariant fields and corresponding univariant curves is the same. Therefore, the relationship between the petrogenetic grids of the pair may be considered as topological homomorphic transformation. The relationships between numbers of invariant points and univariant cur- ves, as well as, between numbers of invariant points and divariant fields in each petrpgenetic grid of six phases of ternary system, can be expressed by two equ- ations; u=i/2(11-i) (1) anmd d=i(9-i)/2+g+1 (2) where u=number of univariant curves; i=number of invariant points; d=num- ber of divariant fields; c=number of indifferent cross points. Besides, another notable point is in that, in the natural world the most widespread paragenetic mineral assemblages are generally of those in the non- cosed divariant fields of the petrogenetic grids.

Abstract:In this study, 109 chemical compositions of clinopyroxene (Cpx) megacrysts were collected from Cenozoic basalts in eastern China. The main characteristics of the. occurrence, physical properties and mineralogical chemistry of the Cpx megacrysts are studied 1 liy. means of large amounts of calculations and projec- tions. The authors present in this paper their own views on the genetic informa- tion of Cpx megacrysts. The compositions of megacrysts were characterized by higher contents of Al2O3 and Al(v1) and moderate Ti and Mg'. But in the "reaction rim" the contents of A1203 Na20, A1 and Al(v1) obviously decreased. The main species of Cpx megac- rysts is augite, while diopside, salite and endiapside are rare. And, the composi- tions of Cpx megacrysts are somewhat varied in .different regions of China.In southern China，the content of Wo' is relatively high with lower A1203; in the north, .Es and Al2O3 are higher; while in the northeast En is higher with mode- rate A1203. The opinions of the authors concerning the genetic information of Cpx me- gacrysts are; 1. The Cpx megacrysts are the products of crystallization of the host basal- tic magma in the upper mantle, but not xenocrystals derived from mantle disin- tegration. 2. The crystallization temperature and pressure of CpX megacrysts in China are 1021-1209℃and 1.4-3.2 Gpa respectively. Therefore the depths of Cpx me- gacrysts crystallization are approximately 48-104 km. The depth is shallower in southern China,deeper in northeastern China and deepest in northern China. The "reaction rim" was formed. at amore shallower mantle`=crust depth. 3. The Cenozoic basalts in eastern China all occur within the continental plate, dominated by alkalibasalts,with little tholeiite the basalts in areas along the basalts, since regions are close marginal sea.

Abstract:The orebodies occur in quartz diorite-porphyry and diorite-porphyrite; which were formed in the early Yanshaniaw orogenic phase and are both: parent !rocks and host rocks of the orebodies. The main metallic minerals are chalcopyrite, pyrite, bornite, native gild and, eiectrum: The main ..gold-containing minerals are pyrite and chalcopyrite. The mode of occurrence of gold in minerals has-been studied by means of ore microscopy, mineral chemistry, phase analysis and electron microprobe and transmission-electron microscope. It is found that micro-goad occurs in chalcopy- rite as inclusions with diairieters of 5-20µ, while submicrogold appears as sphe- rules, chains,. or. in irregular shapes, occurring on the crystal faces or in the microcracks of pyrite. According. to electron probe analysis, the fineness of gold is 790-850 with an average value of 815. Phase analysis showed that the content of gold reach ed 85一95 percent, which indicates that gold occurs as minerals. In China, there is more or‘ less gold' in the porphyry copper ores in districts as Yulong, Dexing, Duobaoshan etc. To find out the enrichment zone such and horizon of gold and its mod-of occurrence will have important significance to development comprehensively the porphyry copper deposits so as to raise their commercial value.

Abstract:In this paper, the typomorphic peculiarities of pyrite in Dachang ore field of Guangxi, China, have been investigated according to chemical compositions and physical properties. It is showed that typomorphic peculiarities of pyrite in Dachang ore field are: higher in S/Fe ratios, richer in As and Se, poorer in Co, Ni and Te, Co/Ni<1, higher positive thermoelectric coefficient, higher unit cell a0 and weak paramagnetism. The microelements of pyrite show that the mineralization of Dachang ore field is related to magmatic hydrothermal solution, and also indicate the evolution trend of mineralization. The different types deposits in the ore field can be distinguished by using Sn/Cu ratios of pyrite. The As-rich pyrite is one of the characteristics of cassiterite-rich ore.

Abstract:The main mineral compositions and microstructures of the low-tenor bauxites from the Xiaoguan deposit, Henan province have been studied with SEM and EDX. These bauxites have been compared with the high-tenor bauxites. It is considered from this that for the low-tenor bauxites the mineral compositions are more complex; several kinds of mineral association are common; the main aluminium mineral is diaspore, but it is lower in purity; the microstructure is more compact than that of the high-tenor bauxites. There are less secondary leaching holes; the crystallinity is also lower. It may be one of the reasons why the performance of technical processing for the low-tenor bauxites is less.