Revisiting effect of ocean diapycnal mixing on Atlantic meridional overturning circulation recovery in a freshwater perturbation simulation

The effects of ocean density vertical stratification and related ocean mixing on the transient response of the Atlantic meridional overturning circulation （AMOC） are examined in a freshwater perturbation simulation using the Bergen Climate Model （BCM）. The results presented here are based on the model outputs of a previous freshwater experiment： a 300-year control integration （CTRL）, a freshwater integration （FW1） which started after 100 years of running the CTRL with an artificially and continuously threefold increase in the freshwater flux to the Greenland-Iceland-Norwegian （GIN） Seas and the Arctic Ocean throughout the following 150-year simulation. In FW1, the transient response of the AMOC exhibits an initial decreasing of about 6 Sv （1 Sv=106 m3 s^-1） over the first 50-year integration and followed a gradual recovery during the last 100-year integration. Our results show that the vertical density stratification as the crucial property of the interior ocean plays an important role for the transient responses of AMOC by regulating the convective and diapycnal mixings under the enhanced freshwater input to northern high latitudes in BCM in which the ocean diapycnal mixing is stratification-dependent. The possible mechanism is also investigated in this paper.     

Evidence for hybridisation in the Tynong Province granitoids,Lachlan Fold Belt,eastern Australia

The role of mafic–felsic magma mixing in the formation of granites is controversial. Field evidence in many granite plutons undoubtedly implies interaction of mafic (basaltic–intermediate) magma with (usually) much more abundant granitic magma, but the extent of such mixing and its effect on overall chemical features of the host intrusion are unclear. Late Devonian I-type granitoids of the Tynong Province in the western Lachlan Fold Belt, southeast Australia, show typical evidence for magma mingling and mixing, such as small dioritic stocks, hybrid zones with local host granite and ubiquitous microgranitoid enclaves. The latter commonly have irregular boundaries and show textural features characteristic of hybridisation, e.g. xenocrysts of granitic quartz and K-feldspars, rapakivi and antirapakivi textures, quartz and feldspar ocelli, and acicular apatite. Linear (well defined to diffuse) compositional trends for granites, hybrid zones and enclaves have been attributed to magma mixing but could also be explained by other mechanisms. Magmatic zircons of the Tynong and Toorongo granodiorites yield U–Pb zircon ages consistent with the known ca 370 Ma age of the province and preserve relatively unevolved ?_Hf (averages for three samples are +6.9, +4.3 and +3.9). The range in zircon ?_Hf in two of the three analysed samples (8.8 and 10.1 ?_Hf units) exceeds that expected from a single homogeneous population (～4 units) and suggests considerable Hf isotopic heterogeneity in the melt from which the zircon formed, consistent with syn-intrusion magma mixing. Correlated whole-rock Sr–Nd isotope data for the Tynong Province granitoids show a considerable range (0.7049–0.7074, ?_Nd +1.2 to –4.7), which may map the hybridisation between a mafic magma and possibly multiple crustal magmas. Major-element variations for host granite, hybrid zones and enclaves in the large Tynong granodiorite show correlations with major-element compositions of the type expected from mixing of contrasting mafic and felsic magmas. However, chemical–isotopic correlations are poorly developed for the province as a whole, especially for ⁸⁷Sr/⁸⁶Sr. In a magma mixing model, such complexities could be explained in terms of a dynamic mixing/mingling environment, with multiple mixing events and subsequent interactions between hybrids and superimposed fractional crystallisation. The results indicate that features plausibly attributed to mafic–felsic magma mixing exist at all scales within this granite province and suggest a major role for magma mixing/mingling in the formation of I-type granites.     

安徽铜陵地区燕山期花岗岩类岩石中的岩浆混合结构

本文采用“结构组合”的概念探讨了铜陵地区花岗岩类岩石中的典型混合结构类型，提出了岩浆混合作用是铜陵地区花岗岩类岩石形成的主要作用，混合作用属于化学混合，且至少发生了两次岩浆混合作用。     

弯段温差剪切分层流断面环流结构与掺混强度研究

对弯段温差剪切分层流的断面环流微细结构与掺混强度特征进行了试验研究。选取45°、90°、1 80°三种不同弯曲度水槽,探求了密度分层流从明显分层到强混合状态下断面环流结构的演变过程,发现了明显分层与强混合两种不同状态下3个环流结构的区别,捕捉到了从分层态向混合态转捩过程中临界情况下四环流结构存在的现象,揭示了明显分层与强混合状态不同断面环流结构的根本机理;同时也对不同弯曲强度情况下掺混强度的沿程变化规律进行探讨与研究。     

内蒙古土牧尔台地区黑云母二长花岗岩及其暗色包体的成因及构造意义

内蒙古中部土牧尔台地区位于华北克拉通北缘,区内广泛发育黑云母二长花岗岩及暗色闪长岩包体,绝大多数包体与寄主岩石呈渐变过渡的接触关系.锆石LA-ICP-MS U-Pb定年结果显示,寄主岩石年龄为273 ～ 271Ma,包体年龄为268±2Ma,两者均形成于早-中二叠世.其中,寄主岩石具有高钾钙碱性、弱过铝质、高分异Ⅰ型花...     

Observations and Simulations of the Circulation and Mixing around the Andaman-Nicobar Submarine Ridge

Using data collected by an Acoustic Doppler Current Profiler(ADCP) on a research cruise in April 2010 in the eastern Indian Ocean,the vertical current structures surrounding the Andaman-Nicobar Submarine Ridge(ANSR) are analyzed to investigate the hydrographic responses to the topography in this region.The results show that the topography of ANSR can induce internal waves around the submarine ridge that have a maximum current velocity of 1 m s-1.The spatial structure of the turbulent kinetic energy(TKE) and shear in this region during 2010 is investigated using the high-resolution Princeton Ocean Model(POM) forced by the satellite-based Advanced Scatterometer(ASCAT) winds including the tide.The results show that the model successfully simulates the internal waves around the ANSR.Numerical experiments further indicate that both the topography and tide play an important role in the generation of the internal waves in this region.     

用单站探空资料分析对流层气柱水汽总量

使用北京地区１９９６,１９９７年７月中至８月上旬常规探空（标准层和特性层）资料,计算了各层气柱的水汽混合比,绘制了水汽垂直分布的廓线,并据水汽廓线分布把大气分为四种类型,通过对各层水汽混合比积分,算出该时段每日０８,２０时的北京单站对流层气柱累积水汽量,研究气柱水汽总量与降水的关系,为预报降水量级,降水范围提供依据,这一分析结果可与辐射仪遥感水汽技术得到的结果进行比较,并为应用其它新的探测技术（如     

Fundamental Framework and Experiments of the Third Generation of IAP/LASG World Ocean General Circulation Model

1.IntroductionThefirstbaroclinicoceanicgeneralcirculationmodel(OGCM)developedattheStateKeyLaboratoryofNumericalModelingforAtmosphericSciencesandGeophysicalFluidDynamics(LASG),InstituteofAtmosphericPhysics(IAP)isafour--layermodelwithitshorizontalresol...     

Mixing of asthenospheric and lithospheric mantle-derived basalt magmas as shown by along-arc variation in Sr and Nd isotopic compositions of Early Miocene basalts from back-arc margin of the NE Japan arc

We report trace element and Sr–Nd isotopic compositions of Early Miocene (22–18 Ma) basaltic rocks distributed along the back-arc margin of the NE Japan arc over 500 km. These rocks are divided into higher TiO₂ (> 1.5 wt.%; referred to as HT) and lower TiO₂ (< 1.5 wt.%; LT) basalts. HT basalt has higher Na₂O + K₂O, HFSE and LREE, Zr/Y, and La/Yb compared to LT basalt. Both suite rocks show a wide range in Sr and Nd isotopic compositions (initial ⁸⁷Sr/⁸⁶Sr (SrI) = 0.70389 to 0.70631, initial ¹⁴³Nd/¹⁴⁴Nd(NdI) = 0.51248 to 0.51285). There is no any systematic variation amongst the studied Early Miocene basaltic rocks in terms of Sr–Nd isotope or Na₂O + K₂O and K₂O abundances, across three volcanic zones from the eastern through transitional to western volcanic zone, but we can identify gradual increases in SrI and decreases in NdI from north to south along the back-arc margin of the NE Japan arc. Based on high field strength element, REE, and Sr–Nd isotope data, Early Miocene basaltic rocks of the NE Japan back-arc margin represent mixing of the asthenospheric mantle-derived basalt magma with two types of basaltic magmas, HT and LT basaltic magmas, derived by different degrees of partial melting of the subcontinental lithospheric mantle composed of garnet-absent lherzolite, with a gradual decrease in the proportion of asthenospheric mantle-derived magma from north to south. These mantle events might have occurred in association with rifting of the Eurasian continental arc during the pre-opening stage of the Japan Sea.     

Concentration Mechanism of Ore-Forming Fluid in Huize Lead-Zinc Deposits, Yunnan Province

The Huize Pb-Zn deposits of Yunnan Province, located in the south-central part of the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn multimetal mineralization district (MMD), are strictly controlled by fault zones. The sources of ore-forming fluid in the deposits have been debated for a long time. Calcite, a gangue mineral, has uniform C and O isotopes. The δ13CPDB and δ18OSMOW values vary respectively from -2.1×10-3 to -3.5×10-3 (mean -2.8×10-3) and 16.7×10-3-18.6×10-3 (mean 17.7×10-3). No obvious difference can be found in C and O isotopes among occurrences and elevations and even ore-bodies. Types of inclusions include those of pure liquid (L), liquid-rich gas-liquid (L V), and three-phase ones containing a daughter mineral (S L V) and immiscible CO2 with three-phases (VCO2 LCO2 LH2O). Their homogenization temperatures vary from 110 to 400 ℃, and two peaks are shown. (87Sr/86Sr)0 ratios of calcite in the deposits are higher than those in the mantle and Emeishan basalts, and slightly higher than those in the Baizuo Formation, which the Huize lead-zinc deposits are found in. All of the (87Sr/86Sr)0 are low relative to those in the basement rocks. Fractionation of Sr isotope did not occur in the ore-forming fluid during the precipitation of minerals. The results indicate that the ore-forming fluid is homogeneous and derived from the mixing of different fluids. Gas-liquid inclusions can be separated into two groups in 300-400 ℃ with a salinity of 5 %-6 % and 12 %-16 % NaCl respectively. However, the salinities of inclusions vary from 7 % to 23 % NaCl in 100-300 ℃, especially in 150-250 ℃. The formation pressures of faulted zones are (50-320)×105 Pa. The estimated pressures of the overlying rocks on the ore bodies are 574×105-640×105 Pa. The pressures of ore-forming processes would be 145×105 to 754×105 Pa. Therefore, pressure sharply reduced and boiling occurred when the ore-forming fluid flew into the fault zones. As a result, the ore-forming fluid was highly concentrated, and metallic minerals began to precipitate from the fluid on a great scale. The high-grade lead-zinc deposits were formed when the fluid was under saturation or over-saturation conditions.