黄土高原黄土粒度的空间变化及其古环境意义

20世纪50~60年代,刘东生先生组织了黄河中游黄土区十条大断面（六纵四横）的野外考察和室内分析,从而证实了从西北到东南黄土粒度逐渐变细的现象,并划分出砂黄土、黄土和粘黄土带。从此,粒度成为黄土研究最基本、最重要的物理指标之一。时至今日,黄土粒度的古气候意义依然有待进一步明确。在前辈研究的基础上,我们对黄土高原57个S2以上剖面进行了详细调查和粒度分析,构建了典型冷暖时期粒度等值线。结果显示,无论是黄土还是古土壤,其粒度均从北向南变细,粒度等值线整体上呈现近东西向展布,表明粒度空间分异以南北向为主。地质记录综合对比显示,沉积区距物源区的距离变化对黄土粒度的影响是第一位的,冬季风风力变化的影响是第二位的。据此,我们构建了"黄土中值粒径-沉积区距源区最小距离"的模型。模型显示：距源区最小距离在400km以内为"快速分异区",粉尘沉积的粒度随搬运距离增加迅速变细,黄土高原黄土即在此区域;在400~2000km间为"缓慢分异区",粉尘粒度随搬运距离的增加缓缓变细,黄土高原新近纪红粘土即为典型代表;距源区2000km以上为粉尘沉积与搬运风力的"平衡区",粉尘粒度随搬运距离增加变化很小,深海粉尘沉积为典型代表。依据低空搬运的黄土"粒度-距离"模型推测的远距离（>2000km）搬运后的粉尘粒度为1~3μm,同高空搬运的北太平洋现代降尘和深海粉尘沉积粒度（2~4μm）非常吻合,表明该模型可能揭示了风力这样一种地质营力的内在动力学特征,这一点需要在今后研究中予以关注。     

青岛崂山晶洞碱性花岗岩同位素地球化学研究

青岛崂山晶洞碱性花岗岩Rb-Sr全岩等时线年龄为134Ma,I_(Sr)=0.7064;石英正长岩和黑云母花岗岩t=146Ma。I_(Sr)=0.7050。青岛岩基全岩的δ~(18)O值为4.8至8.2‰,δD值为-98至-145‰,H_2O含量为0.59至0.07wt％。大气降水热液-岩石相互作用和岩浆开放体系去气作用是造成晶洞碱性花岗岩~(18)O和D贫化的重要原因。     

Last glacial climate instability documented by coarse-grained sediments within the loess sequence, at Fanjiaping, Lanzhou, China

Optically Stimulated Luminescence dating, grain-size analysis and magnetic susceptibility measurements were conducted on the Fanjiaping loess section, from the western Chinese Loess Plateau. The results confirm that last glacial high-frequency climatic shifts were documented in mid-latitude continental archives. The grain-size record indicated that coarse-grained sediments with horizontal bedding and channel-fill structures were only deposited in several short intervals, equivalent to the beginning of marine oxygen isotope stage (MIS) 4 and the early to middle MIS 3. This probably implies brief rainfall intensification of the Asian summer monsoon, and its disappearance since the late MIS 3 to MIS 2 may have been a response to significant glacial cooling in the Northern Hemisphere. Previous investigations revealed high sea-surface temperatures at high latitudes at the start of MIS 4, and the early to middle MIS 3 intensification of summer insolation in the Northern Hemisphere, implying evident climate amelioration. Climate improvement favors boreal forest recovery, enhancing both winter and summer air temperatures. The resultant smaller equator-polar temperature gradient probably helped the moisture-laden summer monsoon to penetrate northward. This study thus provides new significant information about the response of terrestrial loessic palaeoenvironments to millennial-timescale climatic fluctuations during the last glacial period.     

Empirical relationship between leaf wax n-alkane δD and altitude in the Wuyi,Shennongjia and Tianshan Mountains,China: Implications for paleoaltimetry

Estimating past elevation not only provides evidence for vertical movements of the Earth's lithosphere, but also increases our understanding of interactions between tectonics, relief and climate in geological history. Development of biomarker hydrogen isotope-based paleoaltimetry techniques that can be applied to a wide range of sample types is therefore of continuing importance. Here we present leaf wax-derived n-alkane δD (δD_wax) values along three soil altitudinal transects, at different latitudes, in the Wuyi, Shennongjia and Tianshan Mountains in China, to investigate δD_wax gradients and the apparent fractionation between leaf wax and precipitation (ε_wax-p).We find that soil δD_wax track altitudinal variations of precipitation δD along the three transects that span variable environment conditions and vertical vegetation spectra. An empirical δD_wax-altitude relation is therefore established in which the average δD_wax lapse rate of ? 2.27 ± 0.38‰/100 m is suitable for predicting relative paleoelevation change (relative uplift). The application of this empirical gradient is restricted to phases in the mountain uplift stage when the atmospheric circulation had not distinctly changed and to when the climate was not arid. An empirical δD_wax–latitude–altitude formula is also calculated: δD_wax = 3.483LAT ? 0.0227ALT ? 261.5, which gives the preliminary spatial distribution pattern of δD_wax in modern China.Mean value of ε_wax-p in the extreme humid Wuyi Mountains is quite negative (? 154‰), compared to the humid Shennongjia (? 129‰) and the arid (but with abundant summer precipitation) Tianshan Mountains (? 130‰), which suggests aridity or water availability in the growing season is the primary factor controlling soil/sediment ε_wax-p. Along the Tianshan transects, values of ε_wax-p are speculated to be constant with altitude; while along the Wuyi and Shennongjia transects, ε_wax-p are also constant at the low-mid altitudes, but become slightly more negative at high altitudes which could be attributed to overestimates of precipitation δD or the vegetation shift to grass/conifer.Additionally, a reversal of altitude effect in the vertical variation of δD_wax was found in the alpine zone of the Tianshan Mountains, which might be caused by atmospheric circulation change with altitude. This implies that the paleo-circulation pattern and its changes should also be evaluated when stable isotope-based paleoaltimetry is applied.     

Eyes of differing colors in Alvinocaris longirostris from deep-sea chemosynthetic ecosystems: genetic and molecular evidence of its formation mechanism

Journal of Oceanology and Limnology - Coloration is an important phenotypic trait for multiple adaptive functions. It is interesting to find white-eye (AW) and orange-eye (AO) phenotypes in the...     

Abrupt shifts in the late Cenozoic environment of north-western China recorded in loess–palaeosol–red clay sequences

Aeolian deposits can provide a sensitive record of climatic change. Two abrupt changes in grain size and accumulation rate have been identified at c . 2.4–2.6 Ma and 1.1–1.2 Ma in the loess–palaeosol–red clay sequences from the Loess Plateau of China. These changes are apparent in two major stepwise increases in grain size and accumulation rate following two abrupt prominent change events of grain size, implying a two-step reorganization that was probably connected with two abrupt environmental change events. The correlation among different sections suggests that regional rather than local environmental processes are responsible for these changes. These changes likely record abrupt fluctuations in winter monsoon and the provenance of sediments associated with renewed Plio-Pleistocene uplift of the Tibetan plateau, and its role on climate and detrital sediment yield.     

Zircon U-Pb Age and Geochemistry of the Ore-hosting Ultramafic Complex of Zhou’an PGE-Cu-Ni Deposit, Henan Province, Central China

The Zhou’an PGE-Cu-Ni deposit was recently discovered in the Qinling orogenic belt bound by the Yangtze and the North China Cratons. It is a blind deposit thoroughly covered by the Cenozoic alluvial sediments in the Nanyang Basin. As the first large PGE-Cu-Ni deposit discovered in the Qinling-Dabie-Sulu orogenic belt, its geological and geochemical characteristic, isotope age, genesis and tectonic setting are of wide concern in both scientific studies and ore exploration. In this contribution, we report the results obtained from a pioneering study. The Zhou’an ultramafic complex is ferruginous, with m/f?=?4.79–5.08, and shows the nature of tholeiite series. It is rich in light rare earth elements, Rb, Th, U, La, Sm, Zr and Hf, and poor in heavy rare earth elements, Nd and Ta, suggesting an intraplate setting. It has high 87Sr/86Sr and low 143Nd/144Nd ratios. The ratios of Zr/Nb, La/Nb, Ba/Nb, Rb/Nb, Th/Nb, Th/La and Ba/La, suggest the magma originated from lithosphere mantle. The Fo values of olivine and Pd/Ir-Ni/Cu diagram suggest primary magma was High Mg basalt. The laser ablation inductively coupled plasma atomic emission spectroscopy zircon U-Pb age is 641.5?±?3.7 Ma.     

中国岩浆硫化物矿床的主要类型

母岩浆侵入现存空间之前，在深部就已发生了熔离作用和部分结晶作用，致使母岩浆分离为不含矿岩浆、含矿岩浆、富矿岩浆和矿浆，然后对现存空间一次或多次贯入成矿。这种成矿作用是小岩体成大矿的必备条件，这种深部熔离—贯入矿床，是中国最主要的岩浆硫化物矿床类型，也是世界主要的岩浆硫化物矿床类型之一