Perceptions and attitudes of stakeholders towards the wildlife refuge of Ilha dos Lobos,a marine protected area in Brazil     

《Marine Policy》2014

At the north coast of Rio Grande do Sul state, southern Brazilian coast, the Wildlife Refuge of Ilha dos Lobos (29°20′S; 49°43′W), is a full protection area and a seasonal resting refuge for South American sea lions (Otaria flavescens). The regular presence of sea lions on the island is not only a touristic attraction in the region, but also a problem to the fishery community. This community faces economic impacts in its activities due to fish depredation caused by sea lions. Because of this issue, the perceptions and attitudes of different stakeholders from the region are important to be considered by managers, so that a realistic and decentralized action plan can be designed. The goal of this study was to analyze how different local stakeholders perceived the Wildlife Refuge of Ilha dos Lobos. Additionally, how these stakeholders differed from each other in terms of attitudes, knowledge and perceptions. In October 2011, January and March 2012, face-to-face interview surveys were conducted with fishermen and tourists, and drop-off questionnaires surveys with business, and tourism professional and teachers, in a total of 150 questionnaires, 30 for each group. The results indicated existence of differences across the five stakeholder groups. It was also suggested that non-direct stakeholders had a more favorable view of the Wildlife Refuge of Ilha dos Lobos and the sea lion, whereas direct stakeholder (the fishermen) saw it as an obstacle to their fisheries activities.  相似文献   

陕北黄土高原中部生态修复对局地气候的影响     

李明  高维英 《沙漠与绿洲气象(新疆气象)》2024,18(2):156-163

利用陕北黄土高原2000—2019年MODIS产品的MOD13Q1数据，定边、安塞、志丹、子长、延安气象站1990—2019年月（年）平均气温及最高（最低）气温、降雨量、降雨日数等资料，通过差值（比值）、相关系数、线性回归等方法，对陕北黄土高原生态修复显著区（志丹、安塞、子长、延安）和非显著区（定边）在生态修复前（1990—1999年）和生态修复中（2000—2019年）的气象要素变化进行了对比分析。结果表明：（1）生态修复中显著区、非显著区的归一化植被指数随年份以0.123、0.081/10 a增加，显著区的气温上升速率为非显著区的1.5倍；显著区和非显著区年平均气温分别以0.164、0.467 ℃/10 a速率上升，平均降雨量分别以39.95、25.56 mm/10 a的速率增加，显著区较非显著区升温明显缓慢，但平均降雨量的增加速率明显大于非显著区。（2）生态的显著性修复在2012年之后对年平均气温上升的抑制作用凸显，显著区和非显著区年平均气温差值出现突变发生在2013年，此年为生态修复对年平均气温影响的关键时间点；生态修复显著区在植被生长季（4—9月）对年平均气温上升的抑制较为明显，7月最为明显，显著区较非显著区年平均气温降低了1.05 ℃；对最高气温的抑制出现在7—8月，对最低气温的抑制出现在5—6月。（3）生态修复中（2013—2019年）显著区的降雨日数较修复前明显偏少近6 d，其减少主要是小雨日数的减少，中雨以上的降雨日数均随着生态修复的开展呈增加趋势；显著区植被生长季降雨量增加最为明显，降雨量的增加主要表现为中雨以上降雨日数的增加；1—7月随着植被覆盖度不断增加，显著区与非显著区不同等级降雨日数差值逐渐增大，7月达到最大，8—12月，随着植被覆盖度不断降低，降雨日数的差值又逐渐减小。  相似文献   

P–T–t evolution of granulite facies metamorphism and partial melting in the Winding Stair Gap,Central Blue Ridge,North Carolina,USA     

A. K. EL‐SHAZLY  C. LOEHN  R. J. TRACY 《Journal of Metamorphic Geology》2011,29(7):753-780

The Winding Stair Gap in the Central Blue Ridge province exposes granulite facies schists, gneisses, granofelses and migmatites characterized by the mineral assemblages: garnet–biotite–sillimanite–plagioclase–quartz, garnet–hornblende–biotite–plagioclase–quartz ± orthopyroxene ± clinopyroxene and orthopyroxene–biotite–quartz. Multiple textural populations of biotite, kyanite and sillimanite in pelitic schists support a polymetamorphic history characterized by an early clockwise P–T path in which dehydration melting of muscovite took place in the stability field of kyanite. Continued heating led to dehydration melting of biotite until peak conditions of 850 ± 30 °C, 9 ± 1 kbar were reached. After equilibrating at peak temperatures, the rocks underwent a stage of near isobaric cooling during which hydrous melt ± K‐feldspar were replaced by muscovite, and garnet by sillimanite + biotite + plagioclase. Most monazite crystals from a pelitic schist display patchy zoning for Th, Y and U, with some matrix crystals having as many as five compositional zones. A few monazite inclusions in garnet, as well as Y‐rich cores of some monazite matrix crystals, yield the oldest dates of c. 500 Ma, whereas a few homogeneous matrix monazites that grew in the main foliation plane yield dates of 370–330 Ma. Culling and analysis of individual spot dates for eight monazite grains yields three age populations of 509 ± 14 Ma, 438 ± 5 Ma and 360 ± 5 Ma. These data suggest that peak‐temperature metamorphism and partial melting in the central Blue Ridge occurred during the Salinic or Taconic orogeny. Following near isobaric cooling, a second weaker thermal pulse possibly related to intrusion of nearby igneous bodies resulted in growth of monazite c. 360 Ma, coinciding with the Neoacadian orogeny.  相似文献   

Magmatic and geodynamic evolution of Urumieh–Dokhtar basic volcanism,Central Iran: major,trace element,isotopic, and geochronologic implications     

《International Geology Review》2012,54(6):767-786

Basic volcanic rocks from the West Nain area of the Urumieh–Dokhtar Magmatic Assemblage demonstrate significant subduction-related geochemical characteristics; these along with the new age data obtained for the volcanic rocks shed new light on the geodynamic evolution of the Iranian segment of Alpine–Himalayan orogeny. The late Oligocene (26.5 Ma) high-Nb basic volcanic rocks are likely to represent a transient rather enriched asthenospheric mantle underlying the otherwise dominantly Eocene–early Oligocene West Nain island arc. Lithospheric mantle geochemical signatures of the low-Zr volcanic rocks (20.6 Ma) and high-Th volcanic rocks (19.7 Ma) imply replacement of the underlying mantle. The substitution of asthenospheric mantle by a lithospheric mantle wedge might have been associated with – or perhaps caused by – an increase in the subduction rate. Culmination of the West Nain magmatism into slab melting that produced the early Miocene (18.7 Ma) adakitic rocks is compatible with subsequent ascent that triggered slab decompression melting.  相似文献   

Manganese nodule morphology as indicators for oceanic processes in the Central Indian Basin     

《International Geology Review》2012,54(1):27-44

In order to understand the role of geological features in the depositional environment and the prevailing oceanic processes on the formation and characteristics of manganese nodules, a detailed morphological study of the manganese nodules was undertaken on 23,000 nodules from 194 locations (including 801 substations) in a nodule‐rich area covering about 150,000 km² in the Central Indian Basin (CIB). Nodules with rough surface texture dominate most of the area except the south‐eastern part of the basin, which is floored more by the smooth nodules. Smaller nodules (<4 cm) are common and are dominant both in density and mass in the south‐eastern part of the basin, whereas the north‐western part and the central part show dominance of larger rough nodules with higher density and mass. Smooth nodules are also found at shallower depth (<5000 m), on the seamount tops and along the slopes, whereas the rough nodules mostly occur in deeper areas. Significantly, the eastern part of the basin show smooth nodules with smaller size. Smooth nodules >4 cm diameter are rare and show low oxide layer thickness and low bio‐sediment remnants compared to rough surfaced nodules. Large variation in morphological types of nodules are found in the CIB with spheroidal, oblong, triangular, rounded, sub‐rounded or irregular shapes, with irregular nodules being most common. The most common nucleus is altered basalt, while pumice, shark teeth, clay and older nodule nuclei are also present. Water currents and seafloor topography seem to play a major role in defining the nodule morphology. Results of the study show the abundance of smaller nodules with smooth surface texture towards the eastern side of the study area. These features are probably responding to bottom current activity. Inasmuch as the eastern part of the study area is closer to saddles in the Ninety East Ridge (which is the entry point of the Antarctic Bottom Water (AABW) currents into the CIB), the influence of AABW is reflected in the shape and size of the nodules in this area.  相似文献   

Neoarchaean quartz diorites in the Jiefangyingzi area,Central Asian Orogenic Belt: geological and tectonic significance     

《International Geology Review》2012,54(3):358-370

Abstract

Quartz diorite intrusions in the Jiefangyingzi area associated with deformed Palaeozoic rocks of the Palaeozoic Bainaimiao arc magmatic belt on the northern margin of the North China Craton (NCC) were studied to determine their age, chemical composition, and isotopic characteristics. U–Pb dating of magmatic zircons indicates that the quartz diorites formed in Neoarchaean time between 2502.6 ± 9.1 Ma and 2551 ± 7.3 Ma. The quartz diorites have high Al₂O₃ and low K₂O contents, A/CNK = 0.75–0.97, and belong to the low-K tholeiitic series. The quartz diorites are enriched in light rare earth elements (LREEs) with high (La/Yb)_N ratios and exhibit weak positive or no Eu anomalies, characteristics of high-alumina tonalite–trondhjemite–granodiorite (TTG) igneous rocks. Zircon ε_Hf(t) value for the quartz diorites ranges from +1.6 to +8.7, and the two-stage Hf-depleted mantle model age (T_DM) ranges from 2705 to 2744 Ma, suggesting that the quartz diorite was derived from melting juvenile Neoarchaean crust formed from partial melting of the mantle at 2.7 Ga. Amphibolite xenoliths have low REE concentrations and are moderately depleted in LREE with (La/Yb)_N ratios of 0.46–1.09. The trace element characteristics of the amphibolites are consistent with a mid-ocean-ridge basalt (MORB)-like protolith. This is the first time that Archaean rocks have been identified in the Bainaimiao arc magmatic belt and the age and nature of Jiefangyingzi quartz diorites suggest that they belonged to the NCC. The Early Palaeozoic Bainaimiao arc thus appears to represent an Andean-type continental arc on the northern margin of the NCC.  相似文献   

Ordovician volcano–sedimentary iron deposits of the Eastern Tianshan area,Northwest China: the Tianhu example     

《International Geology Review》2012,54(11):1398-1416

ABSTRACT

The stratabound Tianhu iron deposit, with a reserve of 104 Mt at 42% Fe, is located in the eastern part of the Central Tianshan zone in the southern part of the Central Asian Orogenic Belt. The deposit hosts schist, quartzite, marble, amphibolite, and granitic gneiss belonging to the Tianhu Group. Laser ablation inductively coupled plasma mass spectrometry was used to perform zircon U–Pb geochronology, bulk-rock geochemistry, and in situ zircon Hf isotope analyses of the metavolcanic host rocks for constraining the timing and genesis of the Tianhu iron deposit. According to the newly determined age constraints of 452 ± 3 and 477 ± 4 Ma, the iron deposit was concluded to be Ordovician in age. Geochemistry and zircon Lu–Hf isotope analyses suggested that the host rocks of the deposit represent metamorphosed arc-type volcanic rocks generated by the partial melting of a lower crustal source. Combined with geological and ore petrographic characteristics, the Tianhu iron deposit is interpreted to be of volcano–sedimentary origin with enrichment during subsequent metamorphism. The early Palaeozoic marks a critical iron mineralization epoch in the Eastern Tianshan area. The results also support the model of the Central Tianshan area as a volcanic-arc during the early Palaeozoic, associated with the subduction of the Northern Tianshan Ocean.  相似文献   

Partial melting of subducted Southern Qiangtang crust in northern Tibet: evidence from the geochemistry and geochronology of the Riwanchaka granodiorite porphyry in Central Qiangtang     

《International Geology Review》2012,54(6):738-753

ABSTRACT

This article presents new zircon U–Pb geochronology, Hf isotopic, and whole-rock major- and trace-element geochemical data that provide insights into the petrogenesis and tectonic history of the Riwanchaka granodiorite porphyries of Central Qiangtang, Tibet. Zircon U–Pb ages of 236–230 Ma indicate an early Late Triassic age of emplacement of the porphyries, and zircon Hf isotopic data yield εHf(t) values of – 7.0 to – 1.5 and ancient zircon Hf crustal model ages (T_DM^C) of 1524–1220 Ma. The granodiorite porphyries are characterized by low K₂O contents, high Mg# values, and relatively high Cr and Ni contents. They are classified as I-type calc-alkaline granite and are considered to have formed through the anatexis of ancient mafic crustal rocks with contributions from mantle-derived components. The geochemistry and isotopic compositions of all samples are similar to those of magmatic rocks that originated in the South Qiangtang crust. However, field observations indicate that the pluton intrudes the North Qiangtang crust, and we propose that the granodiorite porphyries were derived by partial melting of subducted continental crust of the South Qiangtang terrane. These new data have been integrated with data from previous studies to construct a new model of slab rollback during northward subduction of the Southern Qiangtang continental crust at ca. 245–226 Ma, thereby improving our understanding of magmatic processes involved in continental subduction in collision settings.  相似文献   

Extensional neotectonic regime in West-southwest Konya,Central Anatolia,Turkey     

《International Geology Review》2012,54(14):1803-1821

ABSTRACT

In the Central Anatolia, the style of neotectonic regime governing the region has been a controversial issue. A tectonic study was carried out in order to contribute to this issue and better understand the neotectonic stress distribution and style of deformation in the west-southwest of the Konya region. From Middle Miocene to Recent time, Konya region was part of the Central Anatolia extensional province. The present-day topography in the west-southwestern part of Konya is characterized by alternating elongate grabens and horsts trending E-W and NW-SE. The grabens were developed upon low-grade metamorphic rocks of Palaeozoic and Mesozoic ages and ophiolite slabs of possibly Late Cretaceous age. The evolutionary history of grabens is episodic as evidenced by two graben infills; older and younger graben infills separated by an angular unconformity. The older infill consists of fluviolacustrine sequence intercalated with calc-alkaline lavas and pyroclastic rocks. This infill is folded; thrust faulted and Middle Miocene-Early Pliocene in age. The younger and undeformed basin fill comprises mainly of Plio-Quaternary conglomerates, sandstone-mudstone alternations of alluvial fan and recent basin floor deposits. Three major tectonic phases were differentiated based on the detailed mapping, morphological features and kinematic analysis. Approximately N-S trending extension began in the Middle Miocene-Early Pliocene in the region with the formation of E-W and NW-SE-trending grabens. Following NE-SW-directed compression which deformed the older basin fill deposits by folding and thrusting, a second period of ENE-WSW-trending extension began in the late Pliocene and continued to the present. The west-southwestern margin of the Konya depression is bounded by the Konya Fault Zone. It is an oblique-slip normal fault with a minor dextral strike-slip component and exhibits well-preserved fault slickensides and slickenlines. Recent seismicity and fault-related morphological features reveal that the Konya Fault Zone is an active neotectonic structure.  相似文献   

川中雷口坡组四~3亚段地震相分析——应用波形分类技术研究沉积相的实例     

谷明峰  倪超  辛勇光  吕玉珍  郝毅 《海相油气地质》2012,17(4):68-72

在工区面积大、钻井少的情况下开展地震相研究,可以有效绘出沉积相展布图。对四川盆地中部雷口坡组四3亚段利用GS1和YS104两口井进行地震地质标定,建立了膏盐湖、白云岩坪及颗粒滩等几种不同沉积微相的地震响应模式。膏盐湖相表现为强振幅、高连续的地震响应,而颗粒滩及白云岩坪主要表现为中振幅、低连续的地震响应特征。在地质标定基础上,对全区利用波形分类技术开展地震相研究,恢复了古沉积环境,获得了颗粒滩相及白云岩坪的展布图,这些分布区是有利储层的发育区。龙岗—营山—南充—蓬溪一带处于颗粒滩、白云岩坪有利相带,且处于雷四3亚段地层剥蚀线附近,受岩溶改造强烈,储层较为发育,是川中地区的重要勘探对象。  相似文献