Provenance of Oligocene synorogenic sediments of the Ligurian Alps (NW Italy): inferences on belt age and cooling history

Mineral chemistry, ⁴⁰Ar/³⁹Ar geochronology on white micas and Apatite Fission Track Thermochronology (AFTT), are applied here to study the provenance of the synorogenic Molare Formation (lowermost unit of the Tertiary Piedmont Basin clastic sequence). The Molare Formation was deposited during transgression onto the Ligurian Alps nappe stack in the Early Oligocene. Depositional facies show that clastic distribution remained transversal, with local sources located just landward from the coastline. Phengite mineral chemistry together with ⁴⁰Ar/³⁹Ar data clearly shows two distinctive source areas, each one mirroring the composition of the basement directly beneath the clastic sequence. Amphibole mineral chemistry allows second order provenance distinctions within each sector, reflecting heterogeneous metamorphic evolution of the bedrock complexes. Integrated ⁴⁰Ar/³⁹Ar dating and AFTT suggest that, following a fast cooling/exhumation episode of the Ligurian Alps during the Oligocene, very little net uplift has since occurred. This is due to a period of general subsidence from the Oligocene–Late Miocene followed by comparable uplift from Late Miocene–Pliocene to the present. In general our data provide an image of the Ligurian Alps during the Oligocene, which is very similar to the present-day one.This revised version was published online in September 2003.     

Review on Researches of Aragonite Saturation State in the Southern Ocean:A Key Parameter of Southern Ocean Acidification

The Southern Ocean is a strong sink for atmospheric CO₂, making it especially vulnerable to ocean acidification (OA). The aragonite saturation state (Ω_arg) of seawater has been used as an index for the estimation of OA, which plays a critical role in evaluating the living environment of marine calcified organisms. However, it is very difficult to perform the studies of OA and Ω_arg in the Southern Ocean due to its harsh climate. Therefore, in order to better understand the OA and its further influences, the advances of Ω_arg studies were summarized in the oceans surrounding the Antarctica. Significant spatial and temporal variations of surface seawater Ω_arg are demonstrated in the Southern Ocean. In general, the surface seawater Ω_arg shows a lower value in the off-shore areas than in the open oceans. And, Ω_arg also exhibits a strong seasonal cycle with a higher value in summer than in winter. The distributions of Ω_arg in vertical water column generally present a declining tendency from surface to bottom. In addition, the shoaling of Ω_arg horizon at high latitude could be attributed to the ventilation and upwelling of deep waters in the Southern Ocean. There are many factors that could impact the Ω_arg in the Southern Ocean, including sea ice melting, sea-air CO₂ exchange, biological activities and hydrological processes, etc. Finally, the future changes and key scientific problems of OA in the Southern Ocean are proposed.     

河道砂体内部夹层岩性与遮挡性识别

河道砂体内部夹层作为储层构型界面,厚度较薄,岩性、遮挡性存在差异,对河道砂体内流体渗流及剩余油分布的影响不尽相同。本文以大庆油田萨北二区为例,利用密闭取芯井岩芯和纵向分辨率较高的微电极测井曲线等资料,以岩芯识别夹层岩性为基础,通过对测井曲线幅值、幅差、回返率交汇分析,优选出微电位回返最低值和微梯度回返率作为夹层岩性判别标准,夹层岩性识别符合率达82%;并以夹层含油性为依据,将夹层按遮挡性分为完全阻流型、强限流型、弱限流型等三种类型;分析密闭取芯井河道砂体内部夹层岩性与遮挡性对应关系,建立了非取芯井河道砂体内部夹层遮挡性的岩性解释法,夹层遮挡性识别符合率达72%。以此为深入研究地下河道砂体内部构型对注入剂驱替路径及剩余油分布的影响奠定基础。     

模糊ISODATA法在矿物包裹体成分研究中的应用

矿物包裹体是在成岩成矿过程中保留下来的原始物质,对其成分进行研究,可以提供诸如成岩成矿的物化条件、矿床成因、成岩演化等多方面的信息。就具体矿床而言,成矿物质常常具多源性,矿床的形成往往是各种因素共同作用的产物,其成因具有模糊性。如产于火山岩体或岩浆岩体附近的层控矿床,既具有沉积层控的特点,又受到火山活动或岩浆活动的影响,二者没有一个明确的成因界线。对此模糊现象,运用模糊ＩＳＯＤＡＴＡ法来讨论不同矿床矿物包裹体成分特点,以此探讨矿床的成因类型。     

深基坑承压水的风险控制及处理实例

存在地下承压水的深基坑,当基坑底部承压水层顶部的残留土层不能与承压含水层水头平衡时,处理不当极易造成管涌及坑壁失稳等问题。对相关承压水处理风险源进行分析,针对勘察、设计、施工各阶段都提出具体要求。实例中的基坑临近江面,基坑下承压水与江水存在贯通通道,河道水位变化时会引起承压水头增减,由于设计水头埋深参考值是针对一年观察期而得到的,未考虑到历年水头变化,成为事故埋下隐患,最终因为施工期间河道涨水导致承压水压力超过预期引起了基坑涌水。事故发生后,现场紧急采取堵漏措施,采用灌浆法加固基坑土体,改善土体性质,增加不透水土层的厚度,最终已解决基坑开挖时出现的涌水等现象,保证了工程的顺利安全完成。灌浆法加固是承压水较大情况下基坑安全开挖的有效方式,研究结论对于承压水的风险控制特别是临近江海的工程的设计施工具有较强的指导意义。     

复合胎体金刚石钻头试验研究

为解决坚硬岩层钻进效率低下,研究设计一种复合胎体金刚石钻头,在软岩层进尺快,在硬岩层亦能获得相对较高的钻进速度,突破了单靠降低胎体硬度的传统设计理念,获得了满意钻进效率。     

Monitoring of urban heat island in Shanghai,China, from 1981 to 2010 with satellite data

This paper investigates the urban heat island (UHI) characteristics of Shanghai, China, during 1981–2010 using Landsat thematic mapper/multispectral scanner and moderate-resolution imaging spectroradiometer satellite data from the perspectives of time and space, with further analysis of the landscape pattern, the urban heat island effect ratio, and formative factors. The results show the following: (1) From the interannual variation, the secondary-medium temperature area and the medium temperature area are the main bodies of Shanghai UHI, accounting for 67.16–83.69 % of the total area, and have a rising trend over time. (2) From the landscape pattern, the secondary-medium temperature area and the medium temperature area have a dominant position over the whole UHI landscape pattern of Shanghai; the relatively high-temperature area gradually decreases, and its dominance over the whole UHI landscape pattern declines. (3) From the spatial distribution, the pattern in which the urban area initially had complete domination has gradually transformed to become primarily urban area centered and other construction land supplemented with rapid urbanization. Rapid increase of the green land in the urban area has to some extent reduced the UHI characteristics of the Shanghai area in recent years.     

论找矿勘查的风险性和降低风险的预测性勘查战略

找矿勘查的高风险性表现在找到可赢利矿床的成功率低和找矿发现的成本越来越高,这不仅影响了矿业经济的发展,也影响了公众对地球科学的认识。根据国际找矿勘查的一些统计资料和实例分析了造成找矿勘查高风险性的原因,提出降低风险的预测性勘查战略。区域地质背景、成矿作用的复杂性和勘查者所具有的知识、思维能力、技术手段的局限性等客观因素使找矿勘查的风险不可避免,但不少找矿勘查的失败是由勘查者在资料使用、观察、思维等方面的主观失误造成的。勘查者可以通过增加尝试的次数来获取成功,更可取的是通过提高矿床预测的准确度,以预测性勘查促找矿发现,进而降低找矿勘查的风险。     

藏东南始新世剑川盆地西缘沉积特征及构造意义

印度-欧亚大陆碰撞作用形成了以西藏-喜马拉雅造山带为主体的正向碰撞带和以"三江"造山带为主体的斜向碰撞带,二者之间的现代分界线为喜马拉雅东构造结.剑川盆地是目前已确定的、位于斜向碰撞带最南端的始新世盆地.通过对盆地西缘4条剖面的详细沉积学研究,发现盆地充填过程分为2个阶段.钾质-超钾质火山活动(37～34 Ma)之前的...     

JA96－866型ICAP光电直读光谱仪的智能系统设计

设计了Ｊａｒｒｅｌｌ－Ａｓｂ９６－８６６型电感耦合氩等离子炬（ＩＣＡＰ）光电直读光谱仪与ＩＢＭＰＣ２８６微型计算机的接口适配电路和相应的汇编支持程序，并用ＢｏｒｌａｎｄＣ＋＋２．０面向对象的程序设计语言开发了用户软件，实现了该光谱仪由ＰＤＰ－８Ａ到ＩＢＭＰＣ２８６的计算机换型改造，提高了仪器的智能化水平。