Major Rock Types Research Articles

The Lithofacies Palaeogeography and Control of the Reservoirs in Middle Ordovician Ma5<sub>4</sub><sup>1</sup> Submember in Western Jingbian Tableland

The major rock types of Ordovician Majiagou Formation Ma541 Submember in western Jingbian Tableland include muddy dolomite, gypsum-bearing dolomite, gypsum dolomite, limy dolomite, and muddy powder crystal dolomite. This paper is based on the theory of sedimentary petrology and with the methodology of comprehensive mapping by using single factors to analyze multiple factors.Using stratum thickness, the content of gypsum and penecontemporaneous dolomite as single factors, we studied the lithofacies palaeogeography in Ma541 Submember.The results show that Ma541 is generally a set of sedimentation from supratidal limited evaporation environment and in the period of sea level decline with shallow water. The sedimentary microfacies are mainly composed of gypsum-bearing dolomitic flat and gypsum dolomitic flat ,dolomitic gypsum flat comes second. We combined the areas regional geological background with lithofacies palaeogeography to construct the limited evaporation tidal flat sedimentation maps of Ma541 Submember. Meanwhile,the control of reservoirs was studied. We thought that gypsum-bearing dolomitic flats and dolomitic flats provide a foundation for the development of large-area reservoirs.

Spatial correspondence of knickzones and stream confluences along bedrock rivers in japan: implications for hydraulic formation of knickzones

Knickzones, defined here as locally steep reaches including distinct knickpoints, in bedrock river morphology, have often been investigated in relation to local anomalies in lithology, tectonics, hydraulics, climate and associated base‐level change, and/or deformation of valley‐side slopes. However, exact formative causes of many knickzones in a humid, tectonically active island arc remain unclear. Using databases of geology, streams and knickzones, we examine knickzone distribution across the apanese rchipelago to evaluate the effects of the stream network structure and rock type boundaries on knickzone formation. Knickzones are frequently found just upstream and downstream of major stream confluences along mainstreams, whereas knickzones are less frequent around major rock type boundaries. While the major confluences do not form hanging valleys due to similar catchment size, this observation suggests that many knickzones have been formed by the long‐term effect of flow turbulence scouring bedrock at the confluences. Such a hydraulic control on bedrock erosion in the steep apanese mountains under humid climate conditions indicates that the formative cause of many knickzones therein can be autogenic by means of stream hydraulics.

Spatio-temporal Variation in Radon Concentration in Groundwater with Respect to Rock Types: A Case Study from Chitradurga District, Karnataka

Abstract: An attempt was made in the present study to delineate how the radon concentrations vary with respect to different geological formations and to evaluate annual effective dose exposure due to ingestion of radon. A total of 60 groundwater samples were collected from layered sequential aquifers in Chitradurga district having major rock types such as Bababudan Group, Charnockite, Chitradurga Group, Closepet granite, migmatites and granodiorite – tonalitic gneisses and Sargur Schist complex during pre-monsoon and post-season of the year 2011. Radon measurement was made using Durridge RAD-7 radon-in-air monitor, connected to RAD H2O accessory with closed loop aeration concept. In the present study, the radon activity ranged from 0 to 186.6 Bq/L and 0 to 150.6 Bq/L during pre- and post-monsoon seasons of the year 2011, with 56.67 % (17 samples) of samples during both the seasons exceeding the EPA’s MCL value of 11.1 Bq/L. The annual mean radon activity in the groundwater was higher in the area having Chitradurga rock group formations (78.1 Bq/L) followed by Sargur-Satyamangalam schist complex group (56.8 bq/L), migmatites and granodiorite – tonalitic Gneisses group (56.3 Bq/L), Closepet granite (42.7 Bq/L), Charnonkite (29.1 Bq/L) and Bababudan Group (22.2 Bq/L). It is inferred that radon concentration found to depend on the tectonic structure, geology of the area and on the presence of uranium minerals in these rocks. The annual effective dose resulting from radon in groundwater in the Chitradurga district were significantly lower than UNSCEAR and WHO recommended limit of 1 mSv/y.

Geology and Geochemical Assessment of Metal Contamination of Stream Sediments at Igun and Its Environs, Ilesha Area South Western Nigeria

The cause of heavy metal contamination in stream sediments is probably related to mining activities in Igun study area. Hence the degree of contamination of major and trace elements was carried out to ascertain environmental impact assessment of Igun and its environs, the geology of the study area shows that talc schist, quartzite, amphibolite and granite are the major rock types within the study area, while petrographic studies show quartz, microcline feldspar, biotite, muscovite and hornblende as the main mineral constituents. Total numbers of ten (10) stream sediment samples were collected, air dried at room temperature and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) techniques. From the result of geochemical analysis of the stream sediment samples, the mean concentration for trace elements revealed that Manganese (Mn), Strontium (Sr), Zinc (Zn), Gold (Au) Nickel (Ni), Cobalt (Co) and Lead (Pb) have the mean values of 1704 ppm, 75.11 ppm, 55.80 ppm, 40.22 ppm, 26.15 ppm, 20.94 ppm, 10.60 ppm respectively. The contamination of metals was noticed from the geo accumulation index (Igeo), for stream sediments such as Nickel (0.1), copper (0.5), Manganese (0.6) with Igeo < 1 depicting that these metals are practically uncontaminated. Cobalt (0.1), Zinc (1.1) with Igeo number > 1 < 2 are moderately contaminated and Gold with Igeo of (9.6) indicate very high contamination. In conclusion the results shows that some part of the study area are contaminated and this includes Imoo (location 4), Owena (location 9) and Oke - Ipa (location 1) compared to other locations in the study area which are not contaminated.

Malaysian geotourism – The Langkawi Geopark as a model area

The Langkawi Geopark is one of the first geoparks in the region, created under the auspices of UNESCO and can be considered as a role model not only in South East Asia, but also on a global scale. Presently, the approach towards tourism is holistic, therefore, combining the benefits for the environment, local population and tourists (under the idea of sustainable tourism generally and geotourism in particularly) is essential. On the Langkawi Islands, natural conditions for the development of geotourism are outstanding. They exhibit all the major rock types, beginning with those from the Cambrian period, fossil and faults. The most important however, is the fact that all those geological features are well exposed, and they are easy to reach, since the infrastructure on the island is developed excellently. This paper presents the strategy of development of sustainable tourism / geotourism at the governmental level, the geographical settings of Langkawi and geology of Langkawi, infrastructure of Langkawi Geopark and its applied use.

Identification of the Recharge Sites Using Remote Sensing and GIS in Hard Rock Terrain

Upper Yerrakalava river basin, a part of the Kolleru-Upptuteru catchment lies between Krishna and Godavari river delta is experiencing fall in groundwater levels in recent years. It was identified that groundwater fall is more in sandstone terrain than in khondalitic terrain. To improve the groundwater levels, a study on multi layer analysis was conducted to identify the recharge sites. This included the rainfall and groundwater level analysis, preparation and integration of spatial maps like drainage, lithology, structures, geomorphology and land use/land cover. The final integrated layer was prepared by using weighted aggregation method and was classified into areas of high to low recharge using standard deviation as classification parameter. Remote sensing and GIS techniques were used in preparation of the thematic maps. Geologically, the area had three major rock types namely sandstones, khondalites and granite gneisses. Geomorphologically, 80% of the area was occupied by pediment deeply weathered and pediment moderately weathered material. Crop land and cropland mixed with plantation covered 59% of the area. Rainfall registered an increasing trend in most of the area. The final integrated layer had the recharge areas of very good (2.07%), good (7.15%), moderate (22.8%), poor (56.53%) and very poor (11.44%). Very good recharge locations were identified where fractures were available with good drainage in sandstone terrain, pediplain deeply weathered and double cropped lands. Very poor recharge locations were identified where no fractures and no drainage, steep slopes in khondalitic terrain occupied with forested lands.

Geochronology, petrogenesis and tectonic significance of the Jitang granitic pluton in eastern Tibet, SW China

The Jitang granitic pluton, which is situated in the southern margin of the North Qiangtang block in eastern Tibet, may provide critical information about the source and derivation of the North Qiangtang block during Gondwana breakup and dispersion. In this paper we report relevant data such as zircon U–Pb age, whole-rock major and trace element abundances, and Sr–Nd isotopes for the Jitang pluton. The major rock types of the pluton are granodiorite and biotite granite. Whole-rock major element data reveal that the Jitang pluton is a peraluminous S-type granitic pluton. The U–Pb age of zircons from the pluton is 219.1±1.7Ma, which is ~10Ma younger than the age of high-pressure metamorphism in the Longmu Co–Shuanghu collisional suture between the North and South Qiangtang blocks. The Jitang granitoids show pronounced negative Ba–Eu–Sr anomalies, high initial 87Sr/86Sr ratios from 0.7266 to 0.7389 and low εNd(t) values for from −11.1 to −13.2, which are remarkably similar to the gneisses and meta-sedimentary rocks from the Indian craton as well as the North Qiangtang block. The results from this study indicate that the Jitang granitoids formed by melts derived from a crustal source with Sr–Nd isotopic compositions similar to those of the Indian cratonic crust. We concur with the previous interpretation based on detrital zircon records that the North Qiangtang block was derived from the Indian Gondwana.

Engineering Geological Evaluation of the Spillway of Dam (II-B) of Bunakha Hydroelectric Project, Chukha Dzong, Bhutan

Abstract The 200m long and 106.2m wide spillway of Bunakha Hydroelectric Project is proposed at the centre of the dam to pass the flood discharge. The spillway area was investigated through detailed engineering geological mapping, geophysical survey, exploratory drilling and laboratory testing. The rock mass properties, i.e. joint sets, weathering grade, RQD, RMR, permeability, P-wave velocity etc. of the rock masses to be encountered during the excavation of spillway have been analyzed in detail. Core samples from the exploratory drill hole drilled at the spillway alignment were tested for physico-mechanical properties of rocks in the laboratory. The mapping details indicated that the major rock types which are exposed to the surface and cover the entire spillway area are foliated gneisses with bands of banded gneisses. On the basis of detailed investigations and laboratory testing, inferences and recommendations have been made which will be helpful during the construction of the project.

Textural and Compositional Relationships of Rutile and Chromite in Sittampundi Anorthosite Complex, Tamil Nadu

Abstract The anorthosite complexes and related rock types of the Indian Precambrian shield are primarily associated with either cratons or mobile belts. They were metamorphosed under amphibolites to granulite facies conditions. The major rock types are chromite-bearing meta-anorthosites, amphibolites, basic granulites, pink granites and gneisses. This study was carried out on chromitite bearing samples from Sittampundi layered anorthosite complex, Tamil Nadu, to evaluate the textural and compositional relationships of rutile and chromite. The pristine composition of the chromites is still preserved inspite of intense metamorphic and tectonic process. The rutiles are differentiated into isolated, clustered and exsolved rutile grains.

The mineralogy of propylites of the large Peschanka porphyry copper deposit (West Chukotka)

The Au-Mo-Cu porphyry Peschanka deposit is confined to the Egdygkych Pluton (K1). The deposit comprises three major types of metasomatic rocks: quartz-K-feldspar-biotite, propylites and quartz-sericite. In their chemical compositions, amphiboles of propylites range from early magnesiohornblende to tremolite-actinolite. Compared to magmatic K-feldspar, the metasomatic K-feldspar is enriched in barium (up to 7.3 wt % BaO). Tourmaline belongs to the intermediate member of the oxydravite-povondraite series. The Al content in chlorite decreases to the outer zones of propylitization, which is caused by a decrease in the temperature of mineralization.

The physical parameters of the rocks of the sedimentary cover of the northwestern part of the DnieperDonetsk trough

Density and volume magnetic susceptibility of rocks from 8 boreholes drilled in northwestern part of the DnieperDonets Depression were studied as well as variations of these values for the major rock types found in each of the wells. In accordance with the data the density of rocks of the same type is changed widely for both separate wells and sedimentary cover section as a whole. Decompacted rocks spaces accompanied by increased values of magnetic susceptibility are revealed. Such spaces may be potentially oilandgas bearing.

Phosphorus distribution and fractionation during weathering of amphibolites and gneisses in different climatic setups of the Kaveri river catchment, India

Phosphorus distribution and fractionation during weathering of rocks are seminal to its availability to the life system. Here, the P fractionation pattern is reported in weathering profiles of two different rock types i.e. amphibolites and granitic gneisses, subjected to semi-arid and humid climatic conditions in the catchment of the Kaveri river, southern India, known for its fertile flood plain and delta. Weathering profiles developed on the two rock types were analysed for evaluating the intensity of chemical weathering using major ion geochemistry and for accompanying P fractionation. The Chemical Index of Alteration (CIA) and the mineralogy of different zones of the weathering profiles show that profiles under humid climatic conditions are more weathered than those under semi-arid conditions. It was also found that P, present dominantly as the apatite inorganic P (AIP) fraction in the bedrocks was converted into non-apatite inorganic P (NAIP) and organic P (OP), both of which increase with progressive weathering. The two major rock types show a very similar pattern of P fractionation during weathering which is similar to those observed in soil chronosequences. However, the transfer of P from AIP to OP and NAIP is near total in both rock types under humid conditions of weathering. Under semi-arid conditions, a part of AIP was also available in the most weathered zone. Thus the lithology of the bedrock has little, and climate a dominant, control on P fractionation during rock weathering. It was also observed that there is a net loss of total P during the weathering associated fractionation that could be attributed to the incorporation into biologically available forms and their subsequent removal to the fertile floodplains and delta in an undisturbed riverscape.

Gas-hydrodynamic analysis of the genesis of green and orange glasses in lunar rocks

In order to elucidate the genesis of green and orange glasses in Apollo 15 and Apollo 17 samples of lunar rocks, two alternative hypotheses are analyzed, according to which the glasses are produced either (1) by a comet or meteorite impact (impact model) or (2) by volcanic activity (volcanic model). The green and orange glasses are clearly genetically and petrochemically autonomous, i.e., the composition of the glasses themselves differs from those of the major types of the primary rocks. The mechanisms responsible for the origin of the glasses are analyzed along with mathematical models of their genesis. The theoretically calculated size distribution of glass particles is in good agreement with those measured in Apollo 15 and Apollo 17 samples. Simulation results and the analysis of the composition and structure of the green and orange glasses lead to the conclusion that the impact hypothesis of their genesis is the most realistic.

Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra district, Uttar Pradesh, India

Around 9000 inhabitants in the Panda River basin, Sonbhadhra District, Uttar Pradesh, India, are vulnerable to a “silent” dental and skeletal fluorosis from groundwater consumption. The fluoride source and seasonal groundwater quality variation were studied by collecting 65 groundwater samples in the Upper Panda River basin. Major rock types are phyllites and granite gneissic rocks. Fluoride concentrations are in the range 0.4–5.6 mg/L in the pre-monsoon season and 0.1–6.7 mg/L in the post-monsoon season. Fluor-apatite and biotite mica in the granite gneissic rock were identified as the main provenance of fluoride in the groundwater through water–rock interactions. Due to precipitation of calcium, soils become alkaline with high contents of sodium; these conditions allow fluoride to accumulate in water. According to risk index calculations, the fluoride-affected villages were shown to fall in the fluoride risk zone (with a risk index of around 1.7). On the basis of mineral stability diagrams, groundwater from the weathered and fractured aquifers appears to be stable within the kaolinite field, suggesting weathering of silicate minerals. The groundwater is chemically potable and suitable for domestic and agricultural purposes, except for a few wells in the southern region that are contaminated with high amounts of fluoride. Editor D. Koutsoyiannis Citation Raju, N.J., Dey, S., Gossel, W., and Wycisk, P., 2012. Fluoride hazard and assessment of groundwater quality in the semi-arid Upper Panda River basin, Sonbhadra District, Uttar Pradesh, India. Hydrological Sciences Journal, 57 (7), 1433–1452.

Geochronology–geochemistry of the Cida bimodal intrusive complex, central Emeishan large igneous province, southwest China: petrogenesis and plume–lithosphere interaction

The Cida complex is situated in the Panxi region and is predominantly composed of mafic-ultramafic and syenitic rock units; minor amounts of intermediate rocks occupy the contact zone between the two major rock types. The intermediate unit is mineralogically heterogeneous and typically exhibits a mottled structure. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb zircon dating shows that the mafic-ultramafic rocks and syenitic rocks formed almost coevally (243 ± 0.77 Ma and 240.5 ± 0.76 Ma, respectively). These ages may represent the end phase of the Emeishan large igneous province (ELIP) magmatism. Most of these three rock types possess alkaline and metaluminous affinities. The mafic-ultramafic, syenitic, and intermediate units have K2O + Na2O contents of 1.85–5.16, 6.55–10.46, and 9.55–11.54 wt.%, and SiO2 contents of 40.06–46.70, 61.74–68.54, and 51.57–54.13 wt.%, respectively. The mafic-ultramafic unit displays ocean-island basalt (OIB)-like primitive-mantle-normalized incompatible element patterns, coupled with low initial 87Sr/86Sr ratios (0.7048–0.7064), positive ϵNd(t) (0.32–2.23), and zircon ϵHf(t) (4.53–14.17) values, consistent with a mafic plume-head origin, whereas one exceptional sample with negative ϵNd(t) (–0.22) can be interpreted as due to the involvement of considerable amounts of enriched subcontinental lithospheric mantle. The relatively low (La/Yb) N ratios (3.40–7.69) reflect a spinel-facies lherzolite source. The syenitic unit is characterized by enrichment in large ion lithophile elements (e.g. Rb, K, Pb) and light rare earth elements (LREEs), relative to high field strength elements (e.g. Nb, Ta, P, Ti) and heavy rare earth elements (HREEs), respectively. These features, together with their metaluminous affinities, low SiO2 contents, lower initial 87Sr/86Sr ratios (0.7043), positive ϵNd(t) (0.18), and zircon ϵHf(t) (2.63–10.09) values as well as modelling of REEs, can be plausibly explained by crustal partial melting of juvenile basic materials beneath the Yangtze Block. In contrast, the field, petrographic observations, and geochemical signatures (e.g. the linear correlations between FeO* and MgO, K/Ba and Rb/Ba ratios) suggest that the intermediate unit may have resulted from magma mixing between the syenitic and basaltic magmas that in turn had evolved from a parental mafic-ultramafic liquid. Thus, the formation of the Cida complex can be attributed to the plume–lithosphere interaction plus partial melting of juvenile basic lower crust in response to heating of underplated plume-derived basaltic magma.

Sm–Nd geochronology and geochemistry of a Neoproterozoic gabbro in the Kuluketage block, north-western China

In this article, we report whole-rock and mineral Sm–Nd isotopic and whole-rock elemental and Sr–Nd isotopic data of Xingdi No. 1 mafic–ultramafic intrusion in the western Kuluketage block, north-eastern Tarim. Xingdi No. 1 mafic–ultramafic intrusion is the largest in the Xingdi mafic–ultramafic belt, with an exposed area of ca. 20 km2. It intruded into the Palaeoproterozoic basement. Gabbro is the major rock type and there is minor olivine pyroxenite. Sm–Nd geochronometry of the gabbro gives an isochron age of 761.2 ± 31.2 million years, identical to the intrusive age of Xingdi No. 2 pluton (760 ± 6 million years). The gabbro is systematically enriched in large ion lithosphile elements and light rare earth elements and depleted in high field strength elements and heavy rare earth elements. The studied rocks are characterized by low whole-rock and mineral ϵNd(t) values (−7.8 to −7.1) and elevated (87Sr/86Sr) i values (0.7066–0.7073). These geochemical characteristics, together with the presence of abundant hornblende, biotite, bladed biotite enclosed in amphibole, and crescent-shaped Palaeoproterozoic wall-rock xenoliths in the intrusion, are key features of magma mixing in the source or assimilation during its emplacement. The rocks have a Zr/Y ratio of 3.81–13, which falls in the within-plate basalt area. As Xingdi No. 1 and No. 2 plutons formed at the same period and display similar geochemical characteristics, we propose that they formed within the same tectonic setting and were derived from the same source, but No. 1 pluton experienced a higher extent of evolution and contamination. Previous studies have shown that the Neoproterozoic tectonic and magmatic events in Kuluketage comprise syn-collisional granite around TC (ca. 1.0–0.9 Ga), post-collisional K-rich granite and alkaline mafic–ultramafic intrusions (ca. 830–800 Ma), and rifting-related mafic–ultramafic plutons, dikes, and bimodal volcanic rocks (ca. 774–744 Ma).

Dipole-Dipole Resistivity Measurements of Weathered Soils Over Major Rock Types in a Humid Climate - A Case Study of Ashanti Region-Ghana

Ninety six (96) dipole-dipole resistivity sounding curves acquired with Mac-Ohm II resistivity meter over the Birimian, Intrusives, Tarkwaian and Voltaian rocks underlying Ashanti Region have been analyzed qualitatively to identify their characteristic shapes over each rock type. Geoelectrical sections have also been modeled from the curves and drill logs obtained close to the sounding points. Four (4) major three (3)-geoelectrical sections were identified. These were characterized by the H, A, Q and K- type curves which corresponded to the resistivity sequence r1>r2

Carbonate and sulfate psephites

Major types of coarse-detrital carbonate and sulfate rocks (psephites) are considered. Two large (allochthonous and autochthonous) genetic groups are defined. Characteristics of some representatives are given for each group. It is shown that psephites of the carbonate and sulfate composition differ from similar rocks of the quartz and quartz-silicate composition in terms of formation mechanisms and depositional environments.

GIS를 이용한 경남-울산-부산지역 구성암류의 지질시대별 및 암층별 분포율과 분포특성

암석자원, 산업부지 및 개발계획 등의 지질정보자료로 활용될 수 있도록 분석된 경남, 울산 및 부산지역 구성암류의 지질시대별 암층별 분포율 및 특성은 디음과 같다. 이를 위하여 ArcGIS 9.3, 1 대 250,000 수치지질도 및 수치지형도가 이용되었다. 경남지역의 구성암류는 모두 6개의 지질시대로 구분된다. 분포율은 백악기, 선캠브리아기, 제4기, 쥬라기, 삼첩기 및 제3기의 순으로 감소하고 1.35-57.36%의 범위값을 이루며 그중 전자인 백악기에서 가장 큰 값을 가진다. 구성암층은 모두 40개이며, 그 중 24개가 1.15-13.64%의 다소 좁은 범위 그리고 도합 94.58%를 가져 거의 대부분을 차지한다. 여기에서 가장 우세한 안산암 및 안산암질 응회암은 경남지역의 북동부, 중동부와 남부일대에 발달하며 주변암과 심하게 굴곡진 경계면을 이룬다. 울산지역의 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기 제4기 및 제3기의 순으로 감소하고 6.90-79.21%의 넓은 범위값을 이루며 전자에서 그 값이 크게 증가한다. 구성암층은 모두 1l개이며, 그 중 9개가 1.50-39.0%의 다소 넓은 범위 그리고 도합 98.63%를 가져 그 대부분을 차지한다. 이 중 가장 우세한 진동층은 울산지역 내측부와 동부 일대에 넓게 발달한다. 부산지역 구성암류는 3개의 지질시대로 구분된다. 분포율은 백악기, 제4기 및 제3기의 순으로 감소하며 6.73-47.02%의 범위값을 이루며 전자 둘에서 88.03%를 가져 그 대부분을 차지한다. 구성암층은 모두 10개이며 그 중 6개가 4.07-47.02%의 넓은 분포범위 그리고 도합 93.02%를 가져 거의 대부분을 차지한다. 이 중 뚜렷하게 우세한 충적층은 낙동강 하류, 서낙동강 및 수영강 일대에 발달한다. To get the geologic information data such as rock resources, industrial ground, development planning and so on, distribution ratios of constituent rocks with geologic age and rock type were obtained in Gyeongnam, Ulsan and Busan areas by ArcGIS 9.3 program, digital geologic and geomorphic maps of 1 : 250,000 scale. Geologic ages and rock types in the Gyeongnam area can be divided into 6 and 40, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Precambrian, Quaternary, Jurassic, Triassic and Tertiary. They show the wide ranges of 1.35-57.36%, and the former makes the most dominant ratio. Major rock types are 24 ones, all of which occupy the ratio of 94.58% and relatively narrow ranges of 1.15-13.64% in the area. Among them, andesite and andesitic tuff shows the more or less dominant ratio, and separately develops in the northeast, mid east and south parts of the area. In the Ulsan area, geologic ages and rock types can be divided into 3 and II, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Triassic. They show the very wide range of 6.90-79.21%, and the former makes the most prevailing ratio. Major rock types are 9 ones, which totally occupy the ratio of 98.63% and more or less wide ranges of 1.50-39.01% in the area. Among them, Jindong formation shows the most dominant ratio, and widely develops in the inner and eastern part of the area. In the Busan area, geologic ages and rock types can be divided into 3 and 10, respectively. Their distribution ratios of the geologic ages are decreasing in the order of Cretaceous, Quaternary and Tertiary. They show the wide ranges of 6.73-47.02%, and the two former makes the most dominant ratio of 88.03%. Major rock types are 6 ones, all of which occupy the ratio of 93.02% and relatively wide ranges of 4.07-47.02% in the area. Among them, alluvium forms the most dominant ratio, which mostly develops in the lower Nagdong River, West Nagdong River and Suyeong River.

LA-ICP-MS zircon dating, geochemistry, petrogenesis and tectonic implications of the Dapingliang Neoproterozoic granites at Kuluketage block, NW China

The Kuluketage block, located in the northeast Tarim Craton, is one of the largest Precambrian blocks in Xinjiang Province, China. Recently the Dapingliang skarn Cu deposit was discovered at the eastern part of the Kuluketage block. The ore bodies are developed in skarn rocks along the NE fault. This deposit formed at the middle Neoproterozoic (826Ma) and the ore-related plagiogranite also formed at 826Ma. Plagiogranite, biotite monzogranite and K-feldspar granite are the major rock types intruded in sequence in the Dapingliang area. The LA-ICP-MS zircon 206Pb/238U age of the monzogranite is 816±5Ma. The emplacement age of the Dapingliang granites is then constrained between ca. 816 and 826Ma. Geochemical characteristics show that the rocks belong to the low-Ca, high-K calc alkaline and shoshonite series. They are typical I-type granites. These series have a negative slope from La to Lu. The plagiogranite and biotite monzogranite show no (or weak negative) Eu anomaly, low (La/Yb)N (9.87–23.39), (Dy/Yb)N (1.01–1.14), high Sr (531–976ppm) and Sr/Y (30.5–50.7) with no garnet and plagioclase residual. The K-feldspar granite shows weak to high negative Eu anomaly and relative lower LREE/HREE fractionation. The low La/Yb and Sr/Y show that the origin has plagioclase residual and no garnet residual. Trace elements of the plutons show a negative anomaly of Nb, Ta, P, Zr and Ti, and positive anomaly of Ba, K, Sm and Sr with respect to primary mantle. ɛNd(t) varies from −6.1 to −14.6 and initial 87Sr/86Sr ranges from 0.70235 to 0.70912 for all the samples show lower crust origin and are contaminated with Archean rocks. Pb isotope show low radiogenetic 208Pb/204Pb and 207Pb/204Pb. The initial 208Pb/204Pb and 207Pb/204Pb are well above the Northern Hemisphere Reference Line. The Pb isotopes also indicate lower crust origin. These rocks maybe formed by partial melting of K-rich basalt of the lower crust during a period of transition from crustal compression to extension. There are also K-rich granites formed at the same tectonic setting in the Kuluketage block which contributed to the post-collisional granite belt derived from lower crust.