通过对腾格里沙漠南缘红水河剖面的地层分析和年代序列建立，依据分辨率40～50a的TOC、TIC、元素和稳定同位素（δ180）分析及孢粉分析，重建了腾格里沙漠南缘过渡区全新世8000～3000aBP期间的古气候演变序列。结果显示，（7980）～6870aBP气候变化特点为具振荡性的升温期，且尤以7410～6870aBP最为明显；6870～4620aBP为高温期，并可分为6620～5770aBP温暖而湿润的第1高温期和5360～5130aBP以干热为特征的第2高温期。在5880～5360aBP，即两个高温期之间，气候曾发生持续干化，温度有3次波动降低。第1高温期可被视为本区全新世气候适宜期。5130～4620aBP温度有所降低，但湿度增加，并在4830～4790aBP存在一强降温事件，预示着全新世高温期的衰减；4620aBP开始为降温期并在4620～4320，4010～3590和3270～（3110）aBP出现3次分别与高山冰进相关的低温期。

为探讨华北克拉通中部地壳的磁性结构与深部地质过程之间的相互关系，测量了五台一集宁地壳剖面44件岩石样品的磁性参量及磁滞回线。结合岩石学、地球化学及磁卫星资料的综合研究结果表明，整个断面具有明显的磁性分带结构特征。上地壳、中地壳与下地壳上部岩石饱和磁化强度（Js）的平均值分别为58.7A/m、681.2A/m与1068.0A/m，而饱和等温剩磁JSIRM为4.1A/m、77.9Am和138.4A/m。磁性与变质相及成分对应分析显示，断面内的磁性结构主要受变质作用控制（尤其是变酸性岩与变基性岩）。Js值的变异系数Vc，上地壳为62.2%、中地壳为62.5%、下地壳为143.7%，而JSIRM值的变异系数则分别为70.7%、86.1%、165.4%。中一下地壳之间vC值的差异远大于上一中地壳，显示了地壳深部磁性强度的非均一分布特征。本区中-下地壳岩石的磁化强度明显高于秦岭造山带北缘的登封群与太华群，这一差异可能与两区地壳深部热结构的明显差异相关。结合磁卫星长波长磁异常分析推测，地壳断面中基性麻粒岩的磁性代表了区域下地壳的磁化强度，如果地壳深部的剩余磁性以热粘滞剩磁（TVRT）为主，则可估算出本区下地壳磁化强度约为4.85A/m，与目前世界上许多地盾区下地壳的磁化强度值较为接近。

The Tuoku region in northern Tarim Basin of China is a key area for studying oil/gas reservoir rocks. The magnetic and mineralogical parameters of well cuttings from two wells, well S7, situated on oil/gas field, and well S6, at an oil/water interface, were measured. The two wells are located in the same structure with similar strata and types of lithology, but well S6 is a showing well of oil and gas 5km northwest of well S7. The purpose of this paper is to evaluate the possibility and distribution of secondary magnetic alteration that may have occurred due to hydrocarbon migration above an oil/gas accumulation. It is concluded that the magnetism of well cuttings from major strata in well S7, including source rocks, oil reservoir rocks and cap rocks, and in Quaternary (Q) soil is higher than that from well S6. The Cambrian oil2bearing strata and cap rocks have even higher magnetism in well S7. The shape and parameters of magnetic hysteresis loops indicate that soft (Hc＜20mT, Hs＜0.3T) ferrimagnetic components dominate the magnetic carriers within the strongly magnetic strata of well S7, whereas a mixed paramagnetic and ferrimagnetic distribution occurs in well S6 (for example, low coecivity Hc and nonsaturating magnetized character). Analysis of heavy minerals shows that the contents of iron oxide (magnetite, maghemite and hematite) in well S7 are often higher than those in well S6. The magnetite content in samples of cuttings from Cambrian rocks can reach 9.7% in oil-bearing strata in well S7, and in strata Ekm and N1j are 1.215% and 1.498%, respectively. Typical spherical magnetite grains are found within the main source rocks and the soils in well S7. By analysis of surface microtexture and of trace element contents, we infer that the spherical magnetite is composed of aggregates of ultrafine particles that are probably authigenic magnetite formed in a hydrocarbon halo background.

The Wutai-Jining crustal cross-section is located in the central North China Craton. The upper crustal cross-section is represented by the Wutai granite-greenstone terrain and overlying post-Archean sedimentary rocks, the middle crust by the comparable Henshan and Fuping amphibolite-to granulitefacies terrains, and the upper lower crust by the granulite-facies Jining terrain. Correlation of measured seismic velocities of rocks from the crustal cross-section with data on seismic refractions suggests that the section is likely to represent a ca 30km crust column with the 5 km thick lowermost crust being not exposed (Kern, H., Gao Shan, Liu Qingsheng, 1996. Earth Planet. Sci. Lett. 139, 439-455). Forty-four samples from the cross-section, some of which were used for measurements of seismic velocities and densities (Kern et al., 1996), are analyzed for saturation magnetization (Js) and saturation isothermal remanent magnetization (SIRM). Rock magnetism depends primarily on metamorphic grade and thus on different depth of mineral equilibrium. Lithology plays a less important role. Rocks of greenschist-amphibolite-and granulite-facies have average Js of 58.7, 686 and 1068A/m, respectively. SIRM corresponds to 4.1, 77.9 and 138A/m. Intermediate and felsic granulites from the Jining terrain show even higher magnetism than greenschist-facies metabasalts from the Wutai terrain. Variation coeffcient (Vc) of Js increases from the upper (62.2%) through the middle (64.3%) to the lower (144%) crust. Similarly, SIRM increases from 70.7 to 82.9 and to 165%. This documents considerably greater magnetic heterogeneity in the lower crust compared to the upper and middle crust. For the same lithology, magnetism (Js and SIRM) of rocks from the Jining terrain is remarkably higher than that of rocks from the Archean Taihua granulite terrain at the southern margin of the North China craton adjacent to the Qinling orogenic belt. This is attributed to lower heat flow (52-56mWm-2) in the central North China craton compared to the southern margin of the craton (62mWm-2). Combined with longwavelength magnetic anomalies from Magsat, it is inferred that the mafic ranulite in the cross-section is responsible for lower crustal magnetization in the region. They are comparable to magnetization of lower crust from shield areas in other parts of the world. The strong magnetism of the granulites under this investigation and pyroxenite xenoliths from the nearby Hannuoba alkaline basalt suggest that the magnetic bottom of the lithosphere in the central North China craton lies at the base of the crust or the uppermost mantle.

In the central segment of the Xiangshui-Mandal Geoscience Transect Archean basement rocks of the North China craton are well exposed. The metamorphic grade of the tilted rock units, which are suggested to represent an oblique cross-section through the middle and lower crust, shows a northwestward progressive increase, from the subgreenschist facies to low amphibolite facies Wutai terrain, through the high amphibolite facies Henshan/Fuping terrains, to the granulite facies Jining terrain. We measured compressional wave (Vp) and shear wave (Vs) velocities and densities at confining pressures up to 600 MPa at room temperature and at temperatures up to 600℃ at 600 MPa on 12 representative rock samples from these terrains and determined the pressure and temperature derivatives of the P-and S-wave velocities and densities. The petrophysical data were correlated with chemical and mineralogical characteristics of the rocks. Based on a regional geotherm for a surface heat flow density of 40mW/mz, we calculated velocity-depth profiles for the various lithologies in order to provide clues for a lithological interpretation of the seismic refraction data reported by Maetal. [1]. The two-dimensional interpretation shows four mega-layers (upper crust, middle crust, upper lower crust and lowermost crust) exhibiting different seismic characteristics. The petrophysical and geochemical studies indicate that the middle crust and upper lower crust of the North. China craton are dominated by felsic and mafic rocks that are similar to the Archean amphibolite-granulite facies tonalitic-trondhjemitic-granodioritic gneisses, amphibolites and mafic granulites exposed in this area. The mafic granulites have lower velocities than usual, due to high contents of opaque minerals. The experimental and geochemical data give hints that the rocks representing the high-velocity part of the lowermost crust (Vp＞7kin/s) are not exposed at the surface. The bulk lower crust is suggested to have a relatively evolved, more felsic composition compared to recent estimates for shield/platform areas.

The alteration of iron-bearing minerals induced by hydrocarbon microseepage above oil/gas reservoirs has been evaluated using measurements of soil magnetic susceptibility κ, geochemical compositions (gas hydrocarbon and alteration carbonateΔC), and composition and concentration of iron-bearing minerals. The analyses were performed along two profiles across the Qiangtang basin in Tibet, China: the Nuoermahu-Xuehuanhu profile (C) and the Mugari-Huochetoushan profile (E). Results show that three strong magnetic anomalies (C1, E1 and E2 anomalies) are related to the distribution of Neogene volcanic rocks on the surface in the Gangmacuo-Xiyaergang uplift. Two other anomalies (C2 and E4 anomalies), characterized by both moderately amplitude magnetic susceptibility and elevated soil gas hydrocarbons, occur near fault zones in the Cuoni-Donghu synclinorium. These latter anomalies display characteristics of hydrocarbon microseepage anomalies commonly associated with oil and gas accumulations. Their presence in the Cuoni-Donghu synclinorium suggests that parts of the Qiangtang basin may have significant petroleum potential.

Study of forming mechanism of "chimney-effect" (CE) has important significance for basic theory and applications of non-seismic geophysical and geochemical methods locating oil/gas reservoirs. The theoretical basis of comprehensive evaluation of mechanism of CE using principles of magnetism, geochemistry and mineralogy has been reviewed, with the problems to be solved: (i) study for the relationship between process of oil/gas migration and geochemical field; (ii) analysis of genesis of magnetic, geochemical and mineralogical anomaly; (iii) interpretation of surface soil magnetism and geochemical anomaly combined with seismic data.

In this study, soil magnetic measurements (susceptibility and hysteretic parameters) and soil hydrocarbon analyses were conducted on samples from three profiles (profiles I and II run across, and profile III runs parallel to the trend of the Jingbian gas field in the Ordos basin, central China) to determine the relationship between themagnetic anomalies (e.g., volume-specific magnetic susceptibility k) and the hydrocarbon seepage environments. The results document a strong correlation between magnetic susceptibility and soil-gas hydrocarbon concentration. Furthermore, the spatial distribution of k and hydrocarbon anomalies correlate with those of the gas field. In addition, magnetic minerals in the soils with higher susceptibility are predominantly magnetite, with little or no substitution of titanium compared to that of samples with lower susceptibility (＜7×10-5 SI [International Unit of susceptibility]). These results provide strong evidences for the formation of highly magnetic minerals in close association with hydrocarbon seepage. Recognition of such seepageinduced magnetic anomalies can be used to facilitate the exploration for oil and gas in China and elsewhere.