Acta Geochimica (v.30, #4)
Geochemistry of source rocks in the Es3 and Es4 members in the Shahejie Formation of the Western Depression, Liaohe Oilfield, China by Weili Wang; Luofu Liu; Zhenxue Jiang; Ningning Zhong; Ying Wang; Ping Wang; Lin Wu; Jianghui Meng; Jieli Zhou; Yongqiang Guo (405-414).
The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source rocks are widely distributed in the depression, with semi-deep lake and fan delta as the main sedimentary facies, brown oil shale and black gray-dark gray mudstone as the main rocks, and a total thickness of 270–1450 m. The kerogens are mainly of the types I and IIA, and partly of the type IIB and least of the type III. The R o values range from 0.4%–0.8%, indicating an evolution stage from immature to mature. The maturity of Es4 source rocks is relatively high, reaching the early mature stage, but their distribution and thickness are lower than those of Es3. Besides, according to biomarker analysis, it is thought that the source rocks of Es3 and Es4 are characterized by mixed input, and most of the source rocks were formed in the brackish water-saline and strongly oxygen-free environment. Furthermore, the Qingshui, Niuxintuo and Chenjia sags are believed to possess greater potential for hydrocarbon generation and expulsion, for they are source rocks with a larger thickness, have higher organic carbon contents, belong to better organic matter types and possess higher maturities.
Keywords: source rock; geochemistry; Shahejie Formation; Western Depression; Liaohe Oilfield
Distribution of heavy metals in soils of Port Harcourt and its environs, Niger Delta, Nigeria by Minapuye I. Odigi; Lucky O. Ukren; Hycienth O. Nwankwoala (415-421).
Geochemical evaluation of the distribution of heavy metals in soils of Port Harcourt and its environs in the Niger Delta region is presented in respect of anthropogenic factor and index of geoaccumulation. Sixteen (16) soil samples were collected from two horizons (0–10 cm and 100 cm) from the various grids and analyzed. The geochemical analyses showed the vertical and horizontal distributions of heavy metals. The results showed the ranges of the metals determined as follows: Pb (6.86–2.49)×10−6, with an average of 4.63×10−6; Cd (0.05–0.00)×10−6, with an average of 0.02×10−6, As (0.01–0.00)×10−6, with an average of 0.00×10−6. Cu (15.36–10.80) ×10−6, with an average of 13.36×10−6, and V (1.36–0.20)×10−6, with an average of 0.94×10−6. Quantification of the degree of pollution was carried out using anthropogenic factor (AF) and index of geoaccumulation (I geo). The Igeo values of 0.06, 0.02 and 0.00 for Pb, Cd and As, respectively indicate low-level contamination while Zn (1.14) and V (1.40) show medium-level contamination. The sources of contamination are attributed to urbanized anthropogenic activities. The majority of the samples analyzed show that the AF values are less than 1 with the exception of vanadium (V) whose AF values range from 2.73 to 13.60×10−6. Vanadium is more enriched than As, Cd, Pb, and Cu. The order of degrees of anthropogenic contamination and index of geoaccumulation in the soil is V >Zn >Pb >Cu >Cd >AS. Metals were retained near the top soil and their concentrations in the deepest horizons were lower and normal for uncontaminated soils. Metal concentrations in the top soil horizons were significantly related to distance from the industrial and human activities.
Keywords: heavy metal; contamination; soil; Port Harcourt; Niger Delta; Nigeria
Oxygen isotope and REE geochemistry of metamorphic veins within the Zhoutan Group, central Jiangxi Province by Gongren Hu; Congqiang Liu; Ruilian Yu; Weihe Yu; Yue Liu (422-429).
Geochemical studies on REE, trace elements and oxygen isotopes from metamorphic veins and their host metasedimentary rocks in the Zhoutan Group at two localities, Xiangshan and Yihuang, in central Jiangxi Province have been conducted in this paper. The results show that the metamorphic quartz veins inherited the REE and oxygen isotope geochemical characteristics from their host rocks, suggesting that the vein-forming fluids were derived from the host rocks. Additionally, fractionation degrees of the trace element pairs Zr-Hf, Nb-Ta, Y-Ho and U-Th in the veins are different from those of their host rocks. It is also indicated that the veins are the products of the fluids. The metamorphic veins within the Zhoutan Group metasedimentary rocks were formed principally as a result of lateral diffusion of the metamorphic fluids.
Keywords: metamorphic fluid; oxygen isotope; REE mobility; Zhoutan Group; Jiangxi Province
Mineralogical, REE-geochemical and fluid inclusion studies on some uranium occurrences, Gabal Gattar, Northeastern Desert, Egypt by M. G. El-Feky (430-443).
Altered granite occurrences (GII and GV) at Gabal (G.) Gattar are the most important mineralized rocks hosting U-mineralization in Egypt. This mineralized granite is affected by multi-stage hydrothermal alteration processes along brittle structures. This alteration comprises pre-ore alkali-metasomatism and ore-stage hydrothermal hematitization, silicification, kaolinitization, fluoritization, carbonatization and episyenitization. Autoradiographic examination indicates that primary uranium mineralization is present as massive or disseminated ores along tectonic fractures, interstitially in granular minerals, and as cements of breccias. Uraninite, pitchblende and coffinite are the main primary minerals, while uranophane and kasolite are the secondary ones. Galena, chalcopyrite, pyrrohtite and pyrite are the most abundant sulphides in association with uranium mineralizations. Hydrothermal alterations at the GII occurrence exhibit an increase in Ni, Cu, Zn, Pb, Mo, Nb, Rb beside HREEs and a decrease in Ba, Co, Sr, and V, while alterations at the GV occurrence show enrichment in Ni, Cu, Pb, Mo, Nb, Y, HREEs and depletion in Zn, Ba, Co, Rb, Sr, and V. Hydrothermal alteration during the late magmatic stage is also identified through the development of unusual REE patterns and fractionation of ratios like Zr/Hf and Y/Ho out of the CHARAC (Charge Radius Controlled) range. Non-chondritic Y/Ho ratio at GV is of larger value than chondritic one which may result from water-rock interaction or print from the encompassing sedimentary rocks. Fluid inclusion studies on quartz and fluorite revealed that temperatures of the mineralizing fluids range between 126 and 240°C at pressure ⩽0.5×108 Pa and give salinity values ranging between 1 wt% and 7.8 wt% NaCl equivalent.
Keywords: mineralogy; REE-geochemistry; uranium; granite; mineralization; Egypt
Seasonal variations in sulfur isotopic composition of dissolved SO4 2− in the Aha Lake, Guiyang and their implications by Liuting Song; Congqiang Liu; Zhongliang Wang; Yanguo Teng; Jinsheng Wang; Lili Liang; Li Bai (444-452).
The Aha Lake is a seasonal anoxic water system in the southwest of Guiyang City, Guizhou Province, China. Seasonal variations in SO4 2− concentrations and their isotopic compositions in lake water as well as in the tributaries were investigated in this study. The results showed that sulfate concentrations in river water range from 0.94 to 6.52 mmol/L and their δ34S values range from t14.9‰ and 0.9‰, while lake water has sulfate concentrations ranging from 1.91 to 2.79 mmol/L, and δ34S values from −9.8‰ to −5.9‰. It is suggested that coal mining drainage is the major source of SO4 2− in the Aha Lake. Rainfall, sewage discharge, sulfide oxidation and gypsum dissolution have made only limited contributions. Different depth-dependent distributions of dissolved SO4 2− and δ34S were developed for both DB and LJK in summer and winter. Due to water overturn, δ34S values display homogenous vertical distributions in winter and spring. While in summer and autumn, significant positive shifts of δ34S were clearly observed in epilimnion and bottom strata as a result of water stratification. High δ34S values in epilimnion may result from the retention of rainwater during water stratification. Dissimilatory sulfate reduction by bacteria was thought to be responsible for the increase of δ34S value in hypolimnion.
Keywords: Aha Lake; sulfur isotope; source; geochemical cycling
Mineralogy, geochemistry and age dating of shear zone-hosted Nb-Ta-, Zr-Hf-, Th-, U-bearing granitic rocks in the Ghadir and El-Sella areas, South Eastern Desert, Egypt by M. A. Ali; D. R. Lentz (453-478).
The rare metal minerals of mineralized altered granites within the Ghadir and El-Sella shear zones, are represented by betafite, U-minerals (uraninite and uranophane), zircon, monazite, xenotime, and rutile in the Ghadir shear zone. While they are columbite-tantalite minerals as ferrocolumbite, pyrochlore, and fergusonite, Th-minerals (cheralite, uranothorite, and huttonite monazite), Hf-zircon, monazite and xenotime in the El-Sella shear zone. Hf-zircon in the El-Sella and Ghadir shear zones (increasing from the core to the rim) contains high inclusions of U-Th, and REE minerals such as cheralite, uranothorite, huttonite monazite and xenotime especially in the El Sella shear zone. The rare-metal minerals, identified from peralkminous granites of the shear zones are associated with muscovite, quartz, chlorite, fluorite, magnetite, and biotite that are restricted to the two shear zones. Uraninite (low Th content) occurring in the Ghadir shear zone indicates the hydrothermal origin, but there are thorite, uranothorite, cheralite, and Hf-zircon in the El Sella shear zone, also indicating the hyrothermal proccess after magmatic origin. Compositional variations of Ta/(Ta+Nb) and Mn/(Mn+Fe) in columbite from 0.07–0.42 and 0.04–0.33, respectively, and Hf contents in zircon are so high as to be 12%, especially in the rim in the El Sella shear zone. This feature reflects the extreme degree of magmatic fractionation.Four samples from the altered granites of the Ghadir shear zone also are very low in TiO2 (0.04 wt%–0.17 wt%), Sr [(82−121)×10−6], and Ba [(36−380)×10−6], but high in Fe2O3 T (0.46 wt%–0.68 wt%), CaO (0.64 wt%–1.23 wt%), alkalis (8.59 wt%–8.88 wt%), Rb [(11-203)×10−6], Zr [(98–121)×10−6], Nb [(9-276)×10−6], Ta [(2–139)×10−6], U [(14–63)×10−6], Th [(16–105)×10−6], Pb [(13–32)sx10−6], Zn [(7–8)×10−6], Y [(15–138)×10−6], Hf [(3–9)×10−6], and ΣREE [(81–395)×10−6, especially LREE [(70–322)×10−6]. They are very high in Zr/Hf (15.07–85.96) and Nb/Ta (7.17–21.48), and low in Rb/Sr (2.56–3.36) and Th/U (0.096–3.36). Four samples of the altered granites from the El Sella shear zone are very low in TiO2 (0.23 wt%–0.38 wt%), Sr [(47–933)×10−6], and Ba [(82–175)×10−6], with high Fe2O3 T (1.96 wt%–2.87 wt%), CaO (0.43 wt%–0.6 wt%), alkalis (4.46 wt%–10.7 wt%), Rb [(109–313)×10−6], Zr [(178–1871)×10−6], Nb [(11–404)×10−6], U [(56–182)×10−6], Th [(7-188)×10−6], Ta [(0.5–57)×10−6], Pb [(12–28)×10−6], Zn [(1–13)×10−6], Y [(62–156)×10−6], Hf [(3–124)×10−6], and ζREE [(101–184)×10−6], especially HREE [(7–139)×10−6]. This is consistent with the very fractionated, fluorine-bearing granitic rocks that were altered and sheared in the El Sella shear zone. Zr/Hf (14.23–39.79) and Nb/Ta (1.98–7.01) are very high, and Rb/Sr (0.14–1.7) and Th/U (0.25–2.5) are low in the Ghadir shear zone. Field evidence, textural relations, and the composition of ore minerals suggest that the main mineralizing event was magmatic (615+/−7 Ma, and 644+/−7 Ma CHIME monazite), especially in the El Sella shear zone, with later hydrothermal alteration and local remobilization of the high-field-strength elements.
Keywords: uranium; thorium; zircon; columbite-tantalite; monazite; xenotime; two mica-granite; age dating; Ghadir shear zone; El Sella shear zone; South Eastern Desert, Egypt
Environmental changes during the past 13500 cal. a BP deduced from lacustrine sediment records of Lake Qinghai, China by Yong Wang; Ji Shen; Xingna Xu; Xingqi Liu; Frank Sirocko; Enlou Zhang; Junfeng Ji (479-489).
A 475-cm long sediment core (QH-2005) from Lake Qinghai was used to carry out multi-proxy analysis of δ18O and body length of ostracod valves and redness and grain size of sediments, in order to reconstruct environmental changes during the past 13500 cal. a BP. The age model was based on 6 14C dates for bulk orgnic carbon (BOC) and 2 14C dates for lignin. The lignin 14C dates are apparently younger than the corresponding layers’ BOC 14C dates, indicating that the reservoir age varied from 728 to 1222 a since the Late Glacial and from 2390 to 2490 a immediately before the pre-bomb era. Hence, the 14C age model for Core QH-2005 was corrected by the changing reservoir age. Ostracod δ18O values were primarily related to dilution and evaporative enrichment of the lake water. The reconstructed salinity based on ostracod body length coincides well with ostracod δ18O values. High redness and mean grain size (MZ) values indicate increased riverine supply to Lake Qinghai associated with increasing monsoon rainfall. Multi-proxy results show that climate during 13500–10900 cal. a BP was relatively cold and dry with frequent short-term fluctuations; a warm and wet climate began at about 10900 cal. a BP and culminated around 6500 cal. a BP as a result of monsoon strengthening; the climate became cold and dry afterwards and has remained relatively stable since 3400 cal. a BP. Our data also reveal short-term (millennial/centennial timescales) climatic fluctuations including: Younger Dryas events, ice-rafting events 8 and 1 (by ∼11000 cal. a BP and ∼1600 cal. a BP respectively), 8200 cal. a BP cold event, Little Ice Age and the Medieval Warm Period.
Keywords: ostracod oxygen isotope; ostracod body length; redness; grain size; environmental change; Lake Qinghai
A study on the mixing proportion in groundwater samples by using Piper diagram and Phreeqc model by U. Karmegam; S. Chidambaram; M. V. Prasanna; P. Sasidhar; S. Manikandan; G. Johnsonbabu; V. Dheivanayaki; P. Paramaguru; R. Manivannan; K. Srinivasamoorthy; P. Anandhan (490-495).
Piper (1944) diagram has been the basis for several important interpretations of the hydrogeochemical data. As seen in this diagram, most natural waters contain relatively few dissolved constituents, with cations (metals or bases) and anions (acid radicles) in chemical equilibrium with one another. Apart from the facies representation, the composition of the mixed sample can be identified in terms of the composition of the parental solution. To bring out this advantage of the Piper diagram, a study was conducted in the Kalpakkam region of Tamilnadu, South India. By taking the geology and water table into consideration, two sample locations were selected as parent solution and third one as the mixture sample. All three samples were analyzed for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl), sulphate (SO4) and phosphate (PO4) by Ion Chromatograph (Metrohm IC 861). HCO3 was determined by volumetric titration. The Piper diagram shows that parent solutions clustered towards Na-Mg-Ca-HCO3-Cl and Na-HCO3 facies, and the mixing sample belongs to Na-Mg-HCO3 facies. Phreeqc interactive (Ver 2.8) along with the original composition of the mixture sample was used to correlate the mixing proportion identified by the Piper diagram.
Keywords: hydrogeochemical mixing; groundwater; Piper diagram; Phreeqc; equilibrium
Identical carbon isotope trends of carbonate and organic carbon and their environmental significance from the Changhsingian (end-Permian), Meishan, South China by Yucheng Li; Wenhui Liu; Wanchun Wang; Jianjing Zheng (496-506).
High resolution carbon isotope analyses of carbonate and organic carbon from Meishan, South China showed that the variation of δ13Ccarb is marked by three large positive excursions during the Changhsingian (end-Permian). Carbon isotope stratigraphy during this stage shows three cyclic intervals in δ13Ccarb, with two cycles corresponding to the lower (Paleofusulinid minima Zone) and one corresponding to the upper Changhsingian (P. sinensis Zone). The large positive δ13Ccarb excursions indicate episodes of enhanced burial of isotopically light organic carbon, presumably in response to deep-water anoxia episodically extending into shallow water with the rise of sea level. The organic carbon during the Changhsingian is distinguished into two groups, and the δ13Corg of each group parallels (separately) the more detailed profile of δ13Ccarb, strongly showing that the values of fractionation Δ13Ccab-org remain relatively constant, with only two intervals with anomaly. The enhanced fractionation Δ13Ccab-org with large negative δ13Corg excursions apparently indicates significant inputs from sulfide-oxidizing bacteria and green sulfur bacteria, notably at bed 24 just predating mass extinction. Our evidence appears to support that the extended euxinic water is possible for the main pulse of mass extinction at the end-Permian.
Keywords: carbon isotope stratigraphy; bacterium; extended euxinic; end-Permian
Tectonomagmatic origin of some volcanic and sub-volcanic rocks from the Lower Benue rift, Nigeria by Smart C. Obiora; Nirmal S. Charan (507-522).
Petrological and geochemical studies on some volcanic and sub-volcanic rocks from the Lower Benue rift indicate that they are basalts, basaltic and doleritic sills, trachybasalt and trachyte which generally belong to the alkali basalt series. The alkaline affinity is clearly evident in both their normative and modal mineral compositions, as well as their chemical compositions. The generally high fractionation indices [(La/Yb)N] are 7.06 to 17.65 for the basaltic rocks and 23.59 to 135. 35 for the trachytic rocks, against low values commonly seen in subalkaline (tholeiitic) series, with strong enrichments in the incompatible elements. All this strongly supports their alkaline affinity. The basaltic rocks are generally fine-grained and porphyritic, consisting of phenocrysts of clinopyroxene and olivine in the groundmass of the same minerals together with plagioclase. The clinopyroxene is either diopside or clinoenstatite. The trachyte consists of oligoclase, orthoclase, biotite, quartz and exhibits typical trachytic, flow structure. The basaltic and doleritic sills are commonly altered, with calcite and epidote as common alteration products. This alteration, which is reflected in the erratic behaviour of K2O, MnO and P2O5 on Harker variation diagrams, high values of LOI, strong depletions in the more mobile LILE (Rb, K, Ba and Sr) and high Th/Ta ratios, is attributed to the effects of an aqueous fluid phase and crustal contamination. On the whole, the mineralogical, as well as major-, trace-elements and REE data suggest that the rocks are co-genetic and most likely derived from differentiation of an alkali olivine-basalt magma, generating through variable low degrees of partial melting of probably an enriched lithospheric (upper) mantle following an asthenospheric uplift (mantle plume or intumescence) with HIMU signatures in a within-plate continental rift tectonic setting. This corroborates earlier results obtained for the intrusive rocks in the region.
Keywords: volcanic rock; subvolcanic rock; Lower Benue rift; alkaline affinity; mantle plume; HIMU signature; within-plate continental rift
Joint toxic effects of heavy metals and atrazine on invasive plant species Solidago Canadensis L. by Zhaoxiang Han; Guandong He; Jiahong Wang; Chunxia Lü (523-530).
In this study, the joint effects of Cd(II), Pb(II) and atrazine (ATR) on Solidago Canadensis L. were investigated. The results showed that soil containing Cd, Pb and ATR could inhibit root elongation of Solidago Canadensis L., and that there was a positive linear relationship between the inhibitory rate of root elongation and the concentrations of Pb(II). The mixture of Cd(II) and Pb(II)-ATR in soil showed a significant adverse effect on root and shoot biomass of Solidago Canadensis L. Acetylsalicylic acid (ASA) contents increased slightly at the lower concentrations of Cd(II)-ATR, then decreased when Cd(II)-ATR concentrations were higher than those of 1.0 TUmix(Cd+ATR). The toxic effect of Pb(II)-ATR on the ASA contents of Solidago Canadensis L. was greater than that of Cd(II)-ATR. Soluble sugar contents firstly decreased and then increased with increasing concentrations of Cd(II)-ATR and displayed fluctuation with increasing concentrations of Pb(II)-ATR. Total protein contents increased with increasing concentrations of Cd(II) and Pb(II)-ATR, relative to the control sample. The NP-SH contents showed a significant increase up to 12.2 mg/gfw of Cd(II)-ATR, followed by a significant decline to 4.5 mg/gfw after 14 days of exposure. The effect of Pb(II)-ATR was similar to that of Cd(II)-ATR but the amount of NP-SH was not higher than that of Cd(II)-ATR.
Keywords: joint toxic effect; cadmium (Cd); lead (Pb); atrazine (ATR); Solidago Canadensis L.
Geological characteristics and metallogenic prospect of marine volcanic rock-type copper deposits in eastern Kunlun Mountains area, Xinjiang by Hongwei Han; He Wang; Lunxun Mu; Yong Wei; Jianhong Zhi; Jianhua Yu; Mengyuan Wei (531-538).
The Katelixi Cu-Zn deposit is a marine volcanic rock-type copper deposit discovered for the first time in the Tokuzidaban Group in eastern Kunlun Mountains area. It is hosted in the Lower Carboniferous Tokuzidaban Group volcanic strata. The orebodies are obviously controlled by the strata and their ore-bearing rocks are a suite of greyish-green mafic tuffs, generally parallel-stratiform, stratoid and lenticular in form, occurring in limestone as well as in the contact between limestone and carbon-bearing siltstone. This ore deposit possesses distinct characteristics of marine volcanic rock sedimentaion. The geological, petrochemical and REE characteristics of its occurrence provide strong evidence suggesting that this deposit is of marine volcanic rock sedimention origin, basically identical to those of some typical marine volcanic rock-type copper deposits in Xinjiang and other parts of China. Marine volcanic rocks are well developed in the Lower Carboniferous Tokuzidaban strata in eastern Kunlun Mountains area. In addition to this deposit, we have also found a number of copper polymetallic ore deposits or occurrences in association with marine volcanc activities in many places where there is a good metallogenic prospect. A breakthrough in the understanding of ore prospecting and genesis has not only filled up the gap in prospecting this type of ore deposits in this area, but also is of great significance in directing exploration of this type of ore deposits in this area.
Keywords: eastern Kunlun Mountains; Katelixi Cu-Zn deposit; marine; volcanic rock; copper deposit; sedimentation; metallogenic prospect
Geological characteristics of the Sizhuang gold deposit in the region of Jiaodong, Shandong Province—A study on tectono-geochemical ore prospecting of ore deposits by Jianping Qian; Hongyi Chen; Yong Meng (539-553).
Tectono-geochemical samples were systematically collected from 5 drillcores along the No. 304 exploration line and at the −310 m level under the pit in the mining area, totalling 705 samples from the metamorphic rocks, granites, altered rocks and orebodies, and were determined for their contents of 20 kinds of elements including Au, Ag, As, Sb, Hg, Cu,-Pb, Zn, Sn, Bi, Mo, Co, Ni, Mn, Cr, V, Ti, Ba, Rb, Sr, etc. By using the Surfer software the geochemical exploration line profile maps for the 20 kinds of elements and the curves for the element geochemical contents of individual ore vein groups were established. In conbination with the geochemical map analytical method and Gregorian’s zoning index calculation method, the vertical, longitudinal and lateral zonation sequences of the elements were ascertained and the geochemical three-dimentional zonation model of the primary halos was established on the basis of the analysis of metallogenic structures and alteration zonation. Coupled with the results of analysis of the geology and geochemistry data, it may be concluded that the process of alteration of granites in the mining area is also accompanied with the process of gold enrichment and mineralization. With the intensification of alteration of granites from granite →potash feldspathization granite →sericite-quartz alteration granite, sericite-quartz rocks →beresitized granite, pyrite sericite-quartz rock, silicified granite →gold ore, the contents of thiophile ore-forming elements such as Au, Ag, As, Cu, Bi, Mo, Pb, Sb, Hg, and Sn tended to increase. Factor analysis of trace elements indicated: factor F2 (Au, Ag, Cu, Sn, As) represents the element association brought in at the main stage of hydrothermal metallogenesis; factor F4 (Bi, Sb) and factor F5 (Pb, Zn) represent the ore-forming element association supperposed during the late stage of Au-bearing sulfides. By using the Gregorian’s zoning index and map analysis method we have ascertained the primary halo axial zonation sequence (form frontal halo →tail halo): Pb, Zn, Mn, Ba, Sr, Rb, As, Sb, Ag, Cu, Sn, Mo, Au, Bi, Hg, Ti, Cr, V, Ni, and Co. The geochemical anomalies in the mining area display a tendency of lateral plunging to WS, which is consistent with the lateral plunging of orebodies and mineralization alteration zone. Comprehensive analysis of the results of investigations on ore-controlling structures, mineralization-alteration zonation and geochemical zonation of the primary halos indicates that the gold orebodies in this area are still of greater extension.
Keywords: gold deposit; ore deposit; tectono-geochemistry; geochemical; primary halos; zonation; Jiaodong; Sizhuang
Application of Pb isotopic tracing technique to constraining the source of Pb in the West Lake Longjing tea by Yuanfa Lu; Hongmei Yang; Liyan Ma; Xiqing Chen; Qunying Wang (554-562).
This paper dealt with the Pb contents and Pb isotopic composition of the West Lake Longjing tea. The results showed that in the tea leaves, from young leaf →old leaf →tea limb, the Pb contents tend to increase gradually from 1.63 →4.84 →6.07×10−6, wich revealed that the Pb was accumulated gradually in the tea. After cleaned, the Pb contents of tea leaves were significantly reduced. This indicated that the deposits on the surface of tea leaves made a great contributuion to Pb contents. The survey results for soils in the relevant tea gardens showed that soil from the Longjing tea garden has higher Pb contents, with an average level of 49.6×10−6, two times those of common soils (24×10−6) in China. Results of the systematic analysis for tea, tea garden soil and the samples with the relevant background of the Pb isotopic composition displayed that the Pb isotopic ratio of tea is 206Pb/207Pb=1.164±0.005 (2σ). The ratio of 206Pb/207Pb for the soil gradually decreased from residue phase, soil dilute acid extract phase, and then to urban topsoil, i.e., 1.175 →1.171 →1.170. The 208Pb/(206Pb+207Pb) ratios also show a similar variation trend. 206Pb/207Pb ratios in the samples with the relevant background were: vehicle exhaust, 1.124; coal-combustion, 1.156; atmosphere, 1.168; and water, 1.166. Comparative studies have shown that Pb pollution is popular in the environmental media (soil, atmosphere, water) in Hangzhou. With the aggravation of Pb pollution, the Pb isotopic composition gradually changed from the natural background (soil residues) to the direction of automobile exhaust. This phenomenon could illustrate that the pollution source was the vehicle exhaust, while the coal-combustion contributed little to environmental pollution in Hangzhou. The Pb of the Longjing tea came mostly from soluble phase Pb in the polluted soil. Moreover, secondary pollution was caused by vehicle exhaust.
Keywords: Longjing tea; Pb isotope; Pb source; Hangzhou; West Lake; Longjing tea
Correlation of karst agricultural geo-environment with non-karst agricultural geo-environment with respect to nutritive elements in Guizhou by Rong Chen; Kun Bi (563-568).
The karst area accounts for 61.9% of the total area in Guizhou Province, which gives rise to a fragile environment and backward economy. Comparative studies on the element contents of rock and soil and agriculture production in both carbonate area and non-carbonate area have been made to establish factors leading to low output and poor quality of agricultural products in the karst area. The result shows that there is an apparent lack of nutrient elements in carbonate rocks. The trace element contents of carbonate rocks are only 3532.27×10−6, but those of non-carbonate rocks are 10894.21×10−6. The available element contents in cultivated soil delivered from carbonate rocks are merely 101.4×10−6, but those from non-carbonate rocks are 326.05×10−6. The available element contents and total element contents in cultivated soil delivered from non-carbonate rocks are 3 times higher than those from carbonate rocks. Besides, high-quality agricultural products such as rice, potato and tea are mainly produced in the non-carbonate area. It is indicated that the low output and quality of agricultural products are caused by the above-mentioned low trace element contents and poor agricultural environment. Therefore, a new method of mineral nutrients compensation has been put forward, which is very effective to raise the load-bearing capacity of agricultural environment, agricultural output and quality of agricultural products.
Keywords: karst; agro-ecological geology; nutrient element; Guizhou
Capturing and storage of CO2 by micron-nano minerals: Evidence from the nature by Xumei Mao; Xike Tian; Chengyong Yu (569-575).
The increase of CO2 in atmosphere is a main factor leading to “greenhouse effect”, which causes more and more serious global environmental problems. The reduction of CO2 is a challenge for the survival of human beings, and it is also a big technical problem. CO2 fluid-rock interaction is a key scientific problem involved in geological storage. The CO2 fluid-rock interaction has a variety of multi-scale changes. Due to great differences in the quantity of surface atoms and surface energy between micron-nano-sized minerals, and ions and crystals, the speed and efficiency of CO2 fluid-rock interaction on a micron-nano scale are much higher than those on other scales. As is known from the natural world, the micron-nano structures of pores and the surface chemical modification of natural porous minerals (zeolite, diatomite, sepiolite, palygorskite, halloysite, etc.) should be further investigated, which can be used as the micron-nano -mineral porous materials with high capacity and high efficiency for capturing CO2. Through simulating the adsorption capacity and process of CO2 by minerals in the natural world, the micron-nano technology is applied to calcium- and magnesium-based minerals (olivine, pyroxene, feldspar, clay, etc.) so as to improve the activity of calcium and magnesium and enlarge the reaction contact area. In this way, the efficiency of capturing and storage of CO2 by calcium- and magnesium-based minerals can be greatly improved. These minerals can also be used as the micron-nano-mineral materials with large capacity and high efficiency for capturing and storing CO2.
Keywords: micron-nano mineral; CO2 ; capturing and storage; fluid-rock interaction
Erratum to: Simulating experiment on the enrichment of precious metals in Lower Cambrian black shale series of Hunan and Guizhou provinces by Tao Han; Xiaoqing Zhu; Zengsheng Li (576-576).