Overprinting porphyry‐type veinlets on the intrusive rocks and phreatomagmatic breccias in the Southwest prospect,southwestern Sto. Tomas II (Philex), Baguio District,Philippines     

Avriel Venis L. Cirineo  Akira Imai  Ryohei Takahashi  Redempta P. Baluda  Noel C. Oliveros  Victor B. Maglambayan  Roy Ronald C. Luis  Maria Lourdes M. Faustino  Jacky Almadin 《Resource Geology》2021,71(1):1-40

The Southwest prospect is located at the southwestern periphery of the Sto. Tomas II porphyry copper–gold deposit in the Baguio District, northwestern Luzon, Philippines. The Southwest prospect hosts a copper‐gold mineralization related to a complex of porphyry intrusions, breccia facies, and overlapping porphyry‐type veinlets emplaced within the basement Pugo metavolcanics rocks and conglomerates of the Zigzag Formation. The occurrences of porphyry‐type veinlets and potassic alteration hosted in the complex are thought to be indications of the presence of blind porphyry deposits within the Sto. Tomas II vicinity. The complex is composed of at least four broadly mineralogically similar dioritic intrusive rocks that vary in texture and alteration type and intensity. These intrusions were accompanied with at least five breccia facies that were formed by the explosive brecciation, induced by the magmatic–hydrothermal processes and phreatomagmatic activities during the emplacement of the various intrusions. Hydrothermal alteration assemblages consisting of potassic, chlorite–magnetite, propylitic and sericite–chlorite alteration, and contemporaneous veinlet types were developed on the host rocks. Elevated copper and gold grades correspond to (a) chalcopyrite–bornite assemblage in the potassic alteration in the syn‐mineralization early‐mineralization diorite (EMD) and contemporaneous veinlets and (b) chalcopyrite‐rich mineralization associated with the chalcopyrite–magnetite–chlorite–actinolite±sericite veinlets contemporaneous with the chlorite–magnetite alteration. Erratic remarkable concentrations of gold were also present in the late‐mineralization Late Diorite (LD). High X_Mg of calcic amphiboles (>0.60) in the intrusive rocks indicate that the magmas have been oxidizing since the early stages of crystallization, while a gap in the composition of Al between the rim and the cores of the calcic amphiboles in the EMD and LD indicate decompression at some point during the crystallization of these intrusive rocks. Fluid inclusion microthermometry suggests the trapping of immiscible fluids that formed the potassic alteration, associated ore mineralization, and sheeted quartz veinlets. The corresponding formation conditions of the shallower and deeper quartz veinlets were estimated at pressures of 50 and 30 MPa and temperatures of 554 and 436°C at depths of 1.9 and 1.1 km. Temperature data from the chlorite indicate that the chalcopyrite‐rich mineralization associated with the chlorite–magnetite alteration was formed at a much lower temperature (ca. 290°C) than the potassic alteration. Evidence from the vein offsetting matrix suggests multiple intrusions within the EMD, despite the K‐Ar ages of the potassic alteration in EMD and hornblende in the LD of about the same age at 3.5 ± 0.3 Ma. The K‐Ar age of the potassic alteration was likely to be thermally reset as a result of the overprinting hydrothermal alteration. The constrained K‐Ar ages also indicate earlier formed intrusive rocks in the Southwest prospect, possibly coeval to the earliest “dark diorite” intrusion in the Sto. Tomas II deposit. In addition, the range of δ³⁴S of sulfide minerals from +1.8‰ to +5.1‰ in the Southwest prospect closely overlaps with the rest of the porphyry copper and epithermal deposits in the Sto. Tomas II deposit and its vicinity. This indicates that the sulfides may have formed from a homogeneous source of the porphyry copper deposits and epithermal deposits in the Sto. Tomas II orebody and its vicinity. The evidence presented in this work proves that the porphyry copper‐type veinlets and the adjacent potassic alteration in the Southwest prospect are formed earlier and at a shallower level in contrast with the other porphyry deposits in the Baguio District.  相似文献   

北京市密云区农业土壤重金属元素地球化学特征及生态风险评价   总被引：3，自引：0，他引：3  

段续川  李苹  黄勇  林赟  袁国礼  罗先熔 《现代地质》2018,32(1):95

在北京市密云区西南部农业区系统地采集了1 065件表层土壤样品,对其中Ni、V、Cr、As、Cd、Pb、Zn、Hg 8种重金属元素的含量开展了测试分析。采用多元统计分析法及空间分析法,阐明了这些重金属元素的地球平均化学分布特征,并探讨了其可能的主要来源。结果表明,8种重金属元素主要分为3类：第一类为Ni、V、Cr、As,其含量低于北京地区背景值,其分布主要受成土母质等自然因素的影响;第二类为Cd、Pb、Zn,其平均含量高于背景值,且居民区含量最高。除继承成土母质外,此类元素的分布特征受人为活动影响较大,其中Cd受人为活动影响的程度明显高于Pb和Zn;第三类为Hg,推断大气沉降为影响Hg分布的主要因素。主要采用Hakanson法评价了土壤中重金属的生态风险,结果表明该地区潜在生态危害指数较低。  相似文献   

基于“政策-潜力-意愿”整合视角的村庄分类研究     

杨林朋  芮旸  王昭  李炬霖  李同昇  王秀武  赵孟丽  赵一瑞 《地理研究》2023,42(1):245-261

村庄分类作为乡村地区制定差异化发展政策的科学手段,是认识和明晰区域乡村振兴路径的重要抓手。论文基于乡村地域系统演化规律,综合考虑地方主观发展意愿,构建了一套基于“政策-潜力-意愿”整合视角的村庄分类框架,按照“政策影响?发展潜力+在地发展意愿”的逻辑思路逐级识别村庄类型,并以西峰区100个行政村作为案例区进行实证分析。结果表明：(1)通过梳理现有政策文件,识别出54个村庄的类型,这部分村庄特征相对显著;其余部分村庄通过“发展潜力-在地发展意愿”耦合分析,确定其发展类型;(2)村庄发展潜力与在地发展意愿不完全耦合,其中“高潜力-低意愿”及“低潜力-高意愿”各占39.13%和6.52%;(3)西峰区村庄最终分为就地城镇化类、集聚提升类、城郊融合类、特色保护类、整治改善类及搬迁撤并类等六种类型,论文据此提出相应的乡村振兴途径及措施建议。  相似文献   

基于土地利用转移流的国土空间格局演变及其驱动机制研究——以宁夏原州区为例          下载免费PDF全文

马彩虹  安斯文  文琦  滑雨琪  李聪慧 《干旱区地理》2022,45(3):925-934

提出了基于土地利用转移流的溯源分析法,结合社会网络分析方法与核密度分析法,探究了2000—2018年原州区国土空间格局演变及其动力机制。结果表明：（1） 原州区的三生空间向生产空间增效、生活空间扩容、生态空间提质的方向演化,生产、生活和生态用地结构由2000年的44.76%、2.90%、52.34%调整为2018年的41.17%、6.29%、52.54%。（2） 原州区的三生空间变化与现行国土空间优化目标有较高的契合度,生态用地的转入主要发生在不宜耕作或不宜居住的区域,体现“生态空间山清水秀”导向;生产空间通过坡改梯田、提供灌溉条件以提升水土资源集约利用水平,体现“生产空间集约高效”导向;生活空间的扩张主要发生在居住条件更为适宜的河谷区,体现“生活空间宜居”导向。（3） 三生空间格局演变表现出明显的空间集聚性,呈现出六盘山阴湿区为带状高值区、黄土丘陵沟壑区为散点高值区、清水河谷为团块状高值区的特征,且不同地类变化的空间集聚性特征有所不同。（4） 基于土地利用转移流溯源法提出了原州区三生空间演变的“动力-响应-结果”传导性动力机制;生态建设是国土空间格局演变最重要的驱动力,其次是水土资源集约利用,二者为国土空间格局优化作出重要贡献;水土流失是各类用地向未利用地转化的重要动力,今后仍需加大对水土流失的治理。通过探究经济与生态双重制约区国土空间变化特征及其动力机制,为国土空间优化提供决策参考。  相似文献   

村镇建设用地扩展与生态环境效应的耦合协同规律及类型甄别——以重庆市荣昌区为例     

王成  冀萌竹  代蕊莲  陈静  沈悦 《地理科学进展》2022,41(3):409-422

村镇建设用地扩展不可避免地挤压生态系统空间,打破系统内部原有的生态环境和生物地球化学过程,在生态文明的时代背景下,如何处理好村镇建设用地扩展与生态环境保护的关系对于实现可持续发展至关重要。论文在厘清村镇建设用地扩展与生态环境效应耦合协调机制的基础上,通过构建评价指标体系分析了2008—2018年重庆市荣昌区村镇建设用地扩展与生态环境效应协调发展的时空演变格局并划分耦合协调发展类型。研究发现：① 村镇建设用地扩展与生态环境效应以人类活动为纽带而构成交互耦合体,解析二者的耦合协调关系为理解村镇建设中“发展”与“保护”这对矛盾体提供了通道。② 2008、2013、2018年荣昌区村镇建设用地扩展与生态环境效应的耦合协调度在时间上呈上升趋势,在空间上呈南北高、中间低的分异格局。③ 运用耦合协调模型并结合同步发展模型将荣昌区村镇划分为保护与发展同步型、生态环境支持型、生态环境损耗型3种耦合协调类型。④ 针对各耦合协调类型提出差异化调控策略：保护与发展同步型村镇应兼顾经济发展与生态保护;生态环境支持型村镇可以适量开发未利用地;生态环境损耗型村镇应改变生态环境效应滞后的现状。  相似文献   

校外托餐场所布局选址与影响因素研究——以西安市雁塔区为例     

于悦  李钢  金安楠  黄雨珊  徐蓝青  杨卓 《地理科学进展》2022,41(8):1440-1452

校外托餐场所作为新型教育辅助设施,主要为中小学生提供餐食休息服务,已逐渐成为学生在家和学校之外的第三活动空间,值得从空间视角深入探究。论文以西安市雁塔区为研究区,基于校外托餐场所及相关兴趣点(point of interest,POI)数据,综合运用空间分析、数理统计、实地调研方法,解析校外托餐场所的基本功能、布局选址特征及其影响因素。研究发现：① 校外托餐场所主要服务对象为低年级义务教育阶段具有儿童托管需求的家庭,具有育儿辅助和儿童“中转”“寄存”功能,服务类型包括学生托管、餐饮起居、作业辅导等;② 空间上多分布在雁塔区中部与北部,呈“东—西”走向,与城区空间形态和各街道发展状况相契合,主要开设在传统中多层小区、高层公寓式小区与单位家属院内,集中于1~5层的低楼层;③ 区域人口、教育环境、投资成本和空间位置影响其布局选址,其中中小学数量与分布、小区数量与分布、距中心城区距离影响较为显著。最后,结合需求群体,从城区、街道、门店3个尺度,系统梳理了影响因素,并结合“双减”政策对今后的研究方向进行了展望。  相似文献   

基于两步移动搜寻法的城市居家养老服务设施可达性研究——以大连市沙河口区低龄老年人为例   总被引：2，自引：0，他引：2  

赵东霞  韩增林  王利  杜鹏  付加森 《地域研究与开发》2014,(6)

基于Arc GIS的两步移动搜寻法可以解决设施(供给)与人口(需求)的空间分布差异性及两者可跨越区界的潜在相互作用。通过对大连市沙河口区常住居家低龄老年人与养老服务设施空间可达性进行实证研究,利用两步移动搜寻法获取各服务设施到人口聚居点的可达性数值并利用Map Info绘制成图,得出89个社区供需间潜在的空间可达性呈现优秀、良好、一般和较差4种结果,为大连沙河口区针对低龄老年人居家养老服务设施的发展规划提供辅助决策支持,也展现了两步移动搜寻法在公共服务空间可达性评价方面的作用。  相似文献   

Long-term variations in orographic rainfall: analysis and implications for upland catchments     

《水文科学杂志》2013,58(2):276-291

Abstract

Climatic changes could alter the frequency and magnitude of rainfall events and the distribution of rainfall with altitude, with important consequences for management of aquatic ecosystems, water resources and flood risk. This study investigates changes in observed rainfall amounts across a range of altitudes in the Lake District region, northwest England, and spatial and temporal changes to the orographic “rainshadow” effect. Between the 1970s and 1990s there have been marked changes to the seasonality of precipitation, such that winters have become wetter, and increasingly dominated by heavy precipitation events. The intensity of these events has increased most markedly at higherelevation sites. Such changes could hinder recovery of sensitive upland sites from acidification and increase the risk of downstream flooding. An inter-decadal weakening of the region's rainshadow suggests a greater proportion of winter precipitation crosses the high-elevation Lake District dome. This is linked to changes in the frequency and character of wet weather patterns.  相似文献   

Meteorological drought analysis using data-driven models for the Lakes District,Turkey     

《水文科学杂志》2013,58(6):1114-1124

Abstract

Droughts may be classified as meteorological, hydrological or agricultural. When meteorological drought appears in a region, agricultural and hydrological droughts follow. In this study, the standardized precipitation index (SPI) was applied for meteorological drought analysis at nine stations located around the Lakes District, Turkey. Analyses were performed on 3-, 6-, 9- and 12-month-long data sets. The SPI drought classifications were modelled by Adaptive Neural-Based Fuzzy Inference System (ANFIS) and Fuzzy Logic, which has the advantage that, in contrast to most of the time series modelling techniques, it does not require the model structure to be known a priori. Comparison of the observed values and the modelling results shows a better agreement with SPI-12 and ANFIS models than with fuzzy logic models.  相似文献   

地质信息约束下的三维密度填图技术研究及应用   总被引：5，自引：0，他引：5  

郭冬  严加永  吕庆田  陈向斌  陈应军 《地质学报》2014,88(4):763-776

矿产勘探中应用最广泛、成本最低的方法就是重力和磁法勘探,它们在靶区优选、隐伏矿定位等不同勘查阶段均发挥了重要作用。但是重磁解释的反演结果往往产生多解性,因而需要采用有效方法来减小多解性。无约束的反演通常很难得到符合实际地质情况的解,因此地质约束反演是现阶段降低多解性的主要途径。本文从模型试验入手,开展了三维密度填图技术研究。对比了无约束与有约束以及约束多少的反演效果,结果发现随着约束条件的增加,反演所得的结果与真实情况的吻合度逐渐增加。本文还以安徽省庐枞矿集区为例,探索了地质信息约束下的重力三维填图技术,获得了矿集区地下5km深度的三维密度体,该结果揭示了矿集区主要岩体三维分布、构造的起伏和主要地层的展布。模型试验和实例结果表明:地质信息约束的三维密度填图技术,能够降低反演多解性,提高分辨率,优化反演结果,是现阶段实现矿集区"透明化",发现深部矿产的最有效的方法之一。  相似文献