Science in China Series D: Earth Sciences

SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block, NW China. The plagiogranite intruded the Middle Proterozoic and Lower Carboniferous with an exposure area of ca. 60 km2 and crystallized at 330.7±4.8 Ma. Rock types mainly include tonalite, trondhjemite and minor amounts of diorite and quartz-diorite. Feldspars in the rocks are dominated by oligoclase-andesine, and minor perthite observed locally. The granites are sodic with Na/K ratios (molar) between 4 and 87. Total REE (50–220 ppm) show a clear positive correlation with SiO2. There is no LRRE/HREE fractionation (LaN/YbN=0.5–1.5), medium negative Eu anomalies (δEu=0.3–0.6), high Y content and low Sr/Y ratio (∼1.0). These granites exhibit relatively juvenile Nd T 2DM model ages of 470 to 580 Ma and positive ɛ Nd(331 Ma) values of 6.23 to 7.65. The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites. However, the regional geology, especially its scale, precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma. We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca. 50% partial melting of the juvenile basaltic crust. The primary magma experienced intensive fractionational crystallization, and intruded into the middle to upper crusts to form the granite pluton. In combination with the previous regional geological data, it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.

Các nghiên cứu về kiến trúc reservoir sông chủ yếu tập trung vào các lớp vỏ địa vật lý và trầm tích hiện đại, nhưng hiếm khi nghiên cứu về reservoir dưới lòng đất, do đó có rất ít phương pháp hiệu quả để dự đoán sự phân bố của các kiến trúc reservoir dưới lòng đất. Trong bài báo này, lấy reservoir sông uốn khúc của tầng Guantao tại mỏ dầu Gudao, bồn trũng Jiyang, vùng vịnh Baohai, Trung Quốc làm ví dụ, phương pháp mô hình hóa kiến trúc của reservoir đai uốn khúc phức tạp được đề xuất, bao gồm ràng buộc phân tầng, khớp mẫu và tương tác đa chiều. Các kiến trúc của reservoir sông uốn khúc có thể được chia thành ba cấp độ: khối cát trong kênh uốn khúc, bãi nổi điểm và khối lắng đọng bên. Các mô hình kiến trúc thuộc các cấp độ khác nhau được điều chỉnh với dữ liệu giếng khoan dưới lòng đất (bao gồm dữ liệu giám sát động) tại các cấp độ khác nhau thông qua lỗ một chiều, hình cắt 2D và không gian 3D, và được xác thực với nhau. Sau đó, mô hình 3D ở các cấp độ khác nhau được thiết lập. Đồng thời, mối quan hệ định lượng giữa chiều rộng của dòng sông hoạt động và quy mô của bãi nổi điểm được thiết lập, và quy mô của khối cát lắng đọng bên và các lớp đá phiến được xác nhận thông qua dữ liệu giếng ngang. Nghiên cứu này không chỉ có ý nghĩa quan trọng trong phát triển địa chất, mà còn có thể cải thiện đáng kể việc khai thác mỏ dầu.

Several oil shale beds, over 10 m thick, occur at the base of the first member of the Upper Cretaceous Qingshankou Formation (K2 qn 1) in the Songliao Basin. They act both as excellent source rocks for conventional oil and as potential oil deposit for shale oil production. Here we combine micropaleontology with organic geochemistry to investigate the paleo-depositional environment and organic source characteristics of the oil shales and black shales. Our results indicate that algal remains are dominant microfossils in K2 qn 1 oil shales, and their relatively high abundance suggests a major algal thriving event during the oil shale deposition. The presence of fresh water and brackish water species, Sentusidinium, Vesperopsis and Nyktericysta, and marine or brackish water deltaic and lagoonal species such as Kiokansium and Dinogymniopsis demonstrate that this paleo-continental lake was influenced by marine transgressions at the time of K2 qn 1 oil shale formation. The extremely low pristine/phytane ratios, relatively high abundance of gammacerane and 4-methyl steranes, and low δ13C values of C14-C37 n-alkanes in the oil shale organic extracts indicate the deposition of oil shales in anoxic and highly stratified water columns and the significant contribution of lacustrine algae to sedimentary organic matter. High molecular-weight paraffinic hydrocarbons with unusually high abundance of nC43, nC45, and nC47 may be related to special algal species associated with marine transgression events. The giant water body of Songliao paleo-lake and the change in the organic and chemical environment (such as nutrition source and water column salinity) associated with seawater transgression into the lake are among the most important reasons for oil shales in the Songliao Basin being different from mudstone and oil shale in other rifted basins.

Three synthetic Fe3+ bearing λ-Fe2SiO4 were analyzed using electron probe method, and the Mössbauer spectra of the samples at 298 K, 150 K, and 95 K were measured. Each spectrum at three temperatures is composed of two doublets. These two doublets are assigned to Fe2+ in the octahedral sites and Fe3+ in the tetrahedral sites, respectively. Site occupancies were determined. The results show that Fe3+ and a small amount of Si4+ are in the tetrahedral and octahedral sites, respectively. The average bond lengths of the octahedral and tetrahedral sites were calculated according to the equations primarily given by Hill et al., O’Neill and Navrotsky and modified by the authors. Furthermore, the octahedral and tetrahedral bond lengths were used to calculate cell parameters and oxygen parameters. In addition, Fe3+ line broadening in the Mössbauer spectra of Fe3+ bearing λ-Fe2SiO4 were interpreted by using the next nearest neighbor effects

Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms by the scholars both at home and aboard, the authors conducted the simulation experiments on the electric fields of sandstorm-triggered creeping-saltating sand, suspending sand and watered suspending sand in the large-scale wind tunnel. According to the experimental results the electric field structure and its formation mecha-nism were analysed and discussed, the quantity of electric charges and electric field strength were measured and calculated, and finally several conclusions were drawn.

The widespread Permian carbonate strata outcropped in northwestern Thailand are considered as the evidence for the Late Paleozoic shallow Tethys. Our investigation, however, shows that basalt can be discovered usually under the Permian carbonate sequence in Chiang Mai-Fang area, northwestern Thailand. The basalt belongs to subalkalic basalt and potassic trachybasalt. They are characterized by high P and Ti in major elements, by high content, enriching LREE, lacking δEu anomaly in rare earth elements, and by enrichment of the large ion lithophile element (LILE) (K, Rb, Ba) and high field strength element (HFSE) (Nb, Ta, Zr) in trace elements, which can be compared with the characters of the oceanic island basalt in Three Rivers (Jinsha River, Lancang River, and Nujiang River) area, southwestern China. Therefore, the Permian carbonate in the studied area was deposited on a seamount, rather than on a stable carbonate platform. The oceanic basin is correlated to the Late Paleozoic ocean represented by the Changning-Menglian Belt in southwestern China and they are a major basin of the Paleo-Tethyan Archipelagoes Ocean. The result indicates nonexistence of a Shan-Thai Block in the Late Paleozoic.

On the basis of Parry’s method (1986), an improved method was established to determine the molar volume (V m) and compositions (X) of the NaCl-H2O-CO2 (NHC) system inclusion. To use this method, the determination of V m-X only requires three microthermometric data of a NHC inclusion: partial homogenization temperature $$(T_{h,CO_2 } )$$ , salinity (S) and total homogenization temperature (T h). Theoretically, four associated equations are needed containing four unknown parameters: $$X_{CO_2 } $$ , X NaCl, V m and F (volume fraction of CO2 phase in total inclusion when occurring partial homogenization). When they are released, the V m-X are determined. The former three equations, only correlated with $$T_{h,CO_2 } $$ , S and F, have simplified expressions: $$X_{CO_2 } = f_1 (T_{h,CO_2 } ,S,F), X_{NaCl} = f_2 (T_{h,CO_2 } ,S,F), V_m = f_3 (T_{h,CO_2 } ,S,F).$$ The last one is the thermodynamic relationship of $$X_{CO_2 } $$ , X NaCl, V m and T h: $$f_4 (X_{CO_2 } ,X_{NaCl} ,V_m ,T_h ) = 0.$$ Since the above four associated equations are complicated, it is necessary to adopt iterative technique to release them. The technique can be described by: (i) Freely input a F value (0⩽F⩽1), with $$T_{h,CO_2 } $$ and S, into the former three equations. As a result, $$X_{CO_2 } $$ , X NaCl and the molar volume value recorded as V m1 are derived. (ii) Input the $$X_{CO_2 } $$ and X NaCl gotten in the step above into the last equation, and another molar volume value recorded as V m2 is determined. (iii) If V m1 is unequal to V m2, the calculation will be restarted from “(i)”. The iteration is completed until V m1 is equal to V m2, which means that the four associated equations are released. Compared to Parry’s (1986) solution method, the improved method is more convenient to use, as well as more accurate to determine $$X_{CO_2 } $$ . It is available for a NHC inlusion whose partial homogenization temperature is higher than clatherate melting temperature and there are no solid salt crystals in the inclusion at partial homogenization.

Energy imbalance is a common problem associated with the measurement of surface energy using the eddy covariance method. In the evaluation of the energy balance, people usually pay more attention to the statistical result that the effective energy (the sum of sensible and latent heat) is systematically lower than the available energy (the difference of net radiation and ground heat flux). However, little attention has been paid to the existence of the reversed situation when the effective energy is larger than the available energy or their contribution to the overall energy closure rate. In this paper, based on the analysis of the energy balance on multiple time scales across the maize growth season, we conclude that the non-synchronization of energy components is the main reason for the existence of the reversed case. By shifting the phase of the effective energy components half an hour ahead, the rates of energy closure over all time scales are improved and dramatically reduce the number of the half-hourly samples when the energy ratio exceeds 1 or is below 0.5. According to the characteristics of the energy distribution and transformation over multiple time scales, latent heat is always the main type of energy cost, and the residual of the energy balance increases with the growth of the maize plant surpassing the sensible heat for seventy days. It is suggested that the heat storage and photosynthetic energy play an important role in the energy balance during the growing period of maize.