Geology and inclusion studies on the genesis of the Baolun gold deposit in Hainan Province,South China

The late Triassic Baolun gold deposit hosted by Silurian phyllites is a large‐scale high‐grade gold deposit in Hainan Island, South China. The ores can be classified into quartz‐vein dominated type and less altered rock type. Three mineralization stages were recognized by mineral assemblages. The early stage, as the most important mineralization stage, is characterized by a quartz–native gold assemblage. The muscovite?quartz?pyrite?native gold assemblage is related to the intermedium mineralization stage. In late mineralization stage, native gold and Bi‐bearing minerals are paragenetic minerals. Microthermometry analyses show that the early mineralization stage is characterized by two types of fluid inclusions, including CO₂‐rich inclusions (C‐type) and aqueous inclusions (W‐type). C‐type inclusions homogenize at 276–335°C with an averaged value of 306°C and have salinities of 1.0–10.0 wt% NaCl equivalent (mean value of 4.9 wt% NaCl equivalent). W‐type inclusions homogenize at 252–301°C (mean value of 278°C) with salinity of 4.0–9.7 wt% NaCl equivalent (mean value of 7.4 wt% NaCl equivalent). In intermedium mineralization stage, C‐type and W‐type inclusions homogenize at 228–320°C (mean value of 283°C) and 178–296°C (mean value of 241°C), with salinities of 2.4–9.9 wt% NaCl equivalent (mean value of 6.5 wt% NaCl equivalent) and 3.7–11.7 wt% NaCl equivalent (mean value of 7.7 wt% NaCl equivalent), respectively. No suitable mineral, such as quartz or calcite, was found for fluid inclusion study from late mineralization stage. In contrast, only aqueous inclusions were found from post‐ore barren veins, which yielded lower homogenization temperatures ranging from 168–241°C (mean value of 195°C) and similar salinities (2.6–12.6 wt% NaCl equivalent with averaged value of 7.2 wt% NaCl equivalent). The different homogenization temperatures and similar salinities of C‐type and W‐type from each mineralization stage indicate that fluid immiscibility and boiling occurred. The Baolun gold deposit was precipitated from a CO₂‐bearing mesothermal fluid, and formed at a syn‐collision environment following the closure of the Paleo‐Tethys.     

北部湾沉积物中放射性核素的分布特征与控制因素

北部湾是我国大西南地区重要的海上通道,也是我国重要的渔场之一。本研究利用高纯锗γ谱仪系统分析北部湾表层和柱状沉积物中4种最主要的天然放射性核素(238U、226Ra、228Ra、40K)含量和分布特征。结果显示,北部湾沉积物中放射性核素含量低于我国大部分海域的结果,高于珊瑚礁区的极低放射性水平的结果。北部湾沉积物中4种核素都存在“蝴蝶”状空间分布特征,该特征主要源于沉积物粒径的非线性调控,且与沉积物总有机碳浓度存在正相关。此外,利用Mn和210Pb所指示的氧化还原状态和物理/生物扰动过程也可以对柱状沉积物中氧化还原敏感型核素(比如,238U)分布产生一定的影响。本文从232Th/238U、40K/238U、226Ra/238U活度比值角度,发现北部湾沉积物具有典型的陆源沉积物特征,且显著不同于南海珊瑚礁区中生源沉积物特征。本研究有利于掌握滨海核电发展背景下的北部湾海洋环境中放射性核素水平,揭示核素的“蝴蝶”状分布特征和控制因素,探索基于放射性核素的地球化学新指标在海洋沉积过程中的应用。     

Timing of Magma Mixing in the Gangdisê Magmatic Belt during the India-Asia Collision: Zircon SHRIMP U-Pb Dating

1 IntroductionIt is widely accepted that the collision of India withEurasia proceeded from "soft" to "hard" phases between c.65-70 Ma and c. 45 Ma (Yin and Harrison, 2000; Flower etal., 2001; Dong, 2002; Mo et al., 2003; Zhou et al., 2004,and references therein). Obviously, it is important tounderstand what kind of process took place at the depth ofthe Tibetan Plateau and its timing and geodynamicenvironment responding to the India-Eurasia continentalcollision. The giant Gangdise granito…     

基于目标的相机标定方法

在利用相机成像的几何原理进行三维坐标测量时,相机标定是首先要解决的问题.空间后方交会、直接线性变换及张正友标定法是3种常用的基于目标的标定方法.本文介绍了其基本原理,并分别进行了程序设计和实验验证,分析了3种方法中控制点数量、焦距大小与精度的关系以及方法的优劣性.结果 表明,过多的控制点会导致空间后方交会方法精度下降;随着焦距的增加,空间后方交会和直接线性变换方法的标定精度均有所下降;直接线性变换、空间后方交会、张正友标定法的可靠性、精度均依次降低.     

莱州市土山-东宋铁矿地质特征

通过近几年的地质找矿工作,莱州市土山—东宋地区发现了中型变质沉积铁矿床。矿床产于古元古代粉子山群小宋组二段底部的含铁岩系。矿石工业类型为需选弱磁性铁矿石,主要成因类型为磁铁黑云片岩型、磁铁变粒岩型。矿床范围内共划分了5个矿段40个矿体。该文以此为基础,对矿区地质特征进行分析研究,以期促进山东省铁矿地质勘查工作的开展。     

云贵高原两个国家基准站降水特性比较

为更好地理解和认识小尺度地形对降水特性的影响,利用位于云贵高原地区相近的两个国家基准站太华山和昆明站2006—2018年雨季(5—10月)小时降水资料,统计分析了两站降水精细化的时空特征.结果表明,两站的海拔高度差约500 m、站距约5 km,暖季降水量差异不大,但降水的精细特征却存在明显差异,主要表现为:(1)两站的降水量和平均降水强度年际差异不明显,但太华山站多数年份的降水频次远多于昆明站;(2)降水日变化上,太华山站在11—20时的累积降水量要高于昆明站;两站降水频次均具有双峰型特征,但在03—09时和11—17时太华山站的降水频次要明显高于昆明站,00—13时和21—23时昆明站的平均降水强度高于太华山站.(3)两站的降水事件特征不同,太华山站的降水事件次数和累积降水量都明显多于昆明站,主要由持续时间在6 h以上的降水事件贡献.(4)两站降水事件主要为共有降水事件,降水特性差异也主要由共有降水事件造成.太华山站先开始(结束)降水的共有降水事件次数比昆明站多(少),持续时间(降水频次)比昆明站长(多),短、长时降水事件的降水量(降水频次)比昆明站大(多),平均降水持续时间比昆明站多0.36 h.(5)两站单独降水事件占总降水事件的39.9％,太华山站的单独降水事件数是昆明站的1.83倍,而且平均持续时间长于昆明站.     

Atmospheric Correction Methods for GF-1 WFV1 Data in Hazy Weather

Increasing hazy weather in the eastern area of China limits the potential application of high-resolution satellite data and poses a huge challenge for the atmospheric correction of remote sensing images. Consequently, it is necessary to find the most suitable atmospheric correction method under hazy condition. In this study, five kinds of atmospheric correction models, including 6S, COST, FLAASH, QUAC, and ATCOR2, are applied to the GaoFen-1 Wild Field Camera (GF-1 WFV1) data in the eastern area of China, and examined by both quantitative and qualitative analyses using the measured spectrum data. Experimental results indicated that ATCOR2 achieves the best performance among the atmospheric correction methods qualitatively and quantitatively. Hence, specifically for the study area and GF-1 WFV1 dataset, ATCOR2 is the most suitable atmospheric correction approach under hazy in the eastern area of China.     

A Novel Remote Sensing Image Enhancement Method Using Unsharp Masking in NSST Domain

In order to deal with the pseudo-Gibbs phenomenon and noise interference in the image enhancement, a novel remote sensing image enhancement technique based on unsharp masking and non-subsampled shearlet transform (NSST) is proposed in this paper. The steps of the proposed model are described as follows: Firstly, the input image is decomposed into one low-frequency component and several high-frequency components by the NSST transform; Secondly, the weighted guided image filter is performed on the low-frequency component to improve the contrast of the image, and the hard thresholding is used to suppress the noise of the high-frequency components; Thirdly, the inverse non-subsampled shearlet transform is utilized to reconstruct the image; Finally, the unsharp masking model is performed on the reconstructed image, and the final enhanced image is obtained. Experimental results and comparison analysis demonstrate that the proposed framework outperforms others in terms of remote sensing image enhancement.     

Exposure,vulnerability, and adaptation of major maize-growing areas to extreme temperature

Driven by increasing demand for food and industrial consumption, world’s maize supply is under stress. Besides, the extreme temperature events are now exposing more threat to maize yield with ongoing climate change. Thus, a comprehensive analysis on maize exposure (exposure is defined as the cultivated area which is exposed to extreme temperature stress), vulnerability (here it means how much yield losses with each temperature increase/decrease at a national scale), and adaptation to extreme temperature is essential to better understand the effects on global maize production, especially in major production countries. It was found that warming trends during the growing season have extensively dominated the main maize-growing areas across the globe. And along with this mean temperature trend was the increasing heat stress and decreasing cold stress among most regions. Moreover, from 1981 to 2011, maize yield losses caused by heat stress in China, India, and the USA were 1.13, 0.64 and 1.12% per decade, respectively, while Mexico has been experiencing a reduction of yield loss due to decreased cold stress of 0.53% per decade. Furthermore, during the period of 2021–2051, the extreme heat stress would increase substantially, while the low temperature was estimated to drop slightly during the growing seasons. Such pattern had also been found over the key reproductive stage of maize. Accordingly, through the sensitivity test of two adaption measures, improved high-temperature-tolerant varieties and changing maize calendar earlier could both mitigate extreme meteorological stress on maize, while the former method would be the most effective way to do so. Our study could provide a paradigm for other crops and other countries in the world to analyze their exposure and vulnerability to the temperature stress and make corresponding adaptation measures.

     

新疆库鲁克塔格西段奥陶纪花岗岩体地质特征及构造意义

塔里木盆地北缘是塔里木克拉通与南天山造山带结合部位,发育近东西展布的古生代花岗质侵入岩带,该侵入岩带对探究塔里木北缘构造背景及属性乃至南天山洋演化至关重要。文中研究岩体位于库鲁克塔格西段的博斯腾湖南岸,主要岩性为二长花岗岩,LA ICP MS U Pb锆石年龄分别为(458±3) Ma和(454.6±4.6) Ma,代表花岗岩结晶年龄。地球化学特征显示,花岗岩的SiO2质量分数为71.03%～74.39%,K2O质量分数为4.14%～5.07%,A/CNK=1.03～1.08,属弱过铝质高钾钙碱性I型花岗岩;(La/Yb)N为16.41～37.59,δEu=0.44～0.79,具轻稀土富集、重稀土相对亏损的特征;在原始地幔标准化蛛网图上,样品均明显富集K、Rb、Ba、Th等大离子亲石元素,亏损Ta、Nb、P、Ti等高场强元素。花岗岩岩浆源于下地壳的部分熔融,在熔融过程中源区残留石榴子石和斜长石。综合区域地质资料及前人成果,认为花岗岩形成的动力和热力来源与南天山洋向南俯冲有关,推测在早古生代南天山洋存在双向俯冲,并从奥陶纪开始向南俯冲消减,一直延续到早石炭世,到晚石炭世闭合。