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31.
Geotechnical characterisation of stratocone crater wall sequences, White Island Volcano, New Zealand
Geotechnical characterisation is undertaken for 3 broad units comprising the bulk of the stratigraphy identified on White Island Volcano, Bay of Plenty, New Zealand, an active island stratovolcano. Field and laboratory measurements were used to describe rock mass characteristics for jointed lava flow units, and ring shear tests were undertaken to derive residual strength parameters for joint infilling materials within the lavas. Rock Mass Rating (RMR) and Geological Strength Index (GSI) values were calculated and converted to Mohr-Coulomb strength parameters using the Hoek-Brown criterion. Backanalysis of known landslide scarps was used to derive strength parameters for brecciated rock masses and hydrothermally altered rock masses. Andesite lava flows have high intact strength (σci = 184 ± 50 MN m− 2; γ = 24.7 ± 0.3 kN m− 3) and typically 3 wide, infilled joint sets, one parallel to flow direction and two steeply inclined, with spacings of 0.3-1.7 m. Joints are rough, with estimated friction angles for clean joints of ?j = 42-47°. Joint infill materials are clayey silts derived from weathering of wall rocks and primary volcanic sources; they have low plastic (54%) and liquid (84%) limits and residual strength values of cr = 0 kN m− 2 and ?r = 23.9 ± 3.1°. RMR values range from 70 to 73, giving calculated strength parameters of c′ = 1161-3391 kN m− 2 and ?′ = 50.5-62.3°. Backanalysis suggests brecciated rock masses have c′ = 0 kN m− 2 and ?′ = 35.4°, whereas GSI observations in the field suggest higher cohesion (c′ = 306-719 kN m− 2) and a range of friction angles bracketing the backanalysed result (?′ = 30.6-41.7°). Hydrothermally altered rock masses have c′ = 369 kN m− 2 and ?′ = 14.9°, indicating considerable loss of strength, especially frictional resistance, compared with the fresh lava units. Values measured at outcrop scale in this study are in keeping with other published values for similar volcanic edifices; backanalysed data suggest weaker rock mass properties than those determined at outcrop. This is interpreted as a scale issue, whereby rock mass characteristics of a large rock mass (crater wall scale) are weaker than those of small outcrops, due in part to the overestimation of friction angle from measurements on small exposures. 相似文献
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辉长岩的高压部分熔融实验研究 总被引：8，自引：5，他引：3
利用天然含水辉长岩在１．５～３．０ＧＰａ,９００℃～１４４０℃条件下进行了高温高压部分熔融实验,系统地分析了辉长岩部分熔融后实验产物的岩石学、矿物学、地球化学特征。获得了１）辉长岩的高压熔融曲线,２）辉长岩在不同压力下熔融时,残留相矿物组合及期间矿物相转变与熔融液相成分（相当于安山岩浆）特征。认识了辉长岩与榴辉岩相间的相变关系;辉长岩－榴辉岩－安山岩之间的内在联系以及高温榴辉岩的可能成因。 相似文献
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Zircon U–Pb Geochronology,Elemental Geochemistry and Geological Implications of the Andesite of the Yixian Formation in the Tiejiangyingzi Basin in Southeastern Chifeng,China 
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下载免费PDF全文 Chun‐Guang Wang Feng‐Yue Sun Guo‐Sheng Sun Yang Li Jiu‐Da Sun Hong‐Da Feng 《Resource Geology》2016,66(2):149-162
The Early Cretaceous andesite of the Yixian Formation is an ore‐host rock in the Tiejiangyingzi basin in southeastern Chifeng, China, and bears several meso‐epithermal Au deposits, such as the Nalingou and Yaogou Au deposits. The geochronology and elemental geochemistry of the Yixian Formation were investigated to reveal its metallogenic context, petrogenesis, and mineralization contribution. The 206Pb/238U ages of zircons reveals that the andesite formed at 125.5 ± 0.9 Ma. This rock belongs to calc‐alkali rock series according to its elemental geochemical analysis results (i.e., SiO2 = 63.63%–67.27%, MgO = 1.17%–1.43%, K2O = 4.07%–4.67%, Mg# = 35–41, Al2O3 = 17.16%–18.63%, Na2O = 3.35%–4.08%, Sr = (240.1–585.6) × 10‐6, Yb = (1.83–2.22) × 10‐6, Y = (13.9–23.36) × 10‐6, Na2O/K2O = 0.7–0.9, Eu/Eu* = (0.75–0.79) × 10‐6, Sr/Y = 13–27, LaN/YbN = 11–19 ). The chondrite‐normalized trace element plot shows that the andesite is enriched in light rare earth elements (LREEs) and Yb. Thus, the residual phase of andesite volcanic rocks is a granulite suite that contains amphibole and little remaining garnet in the Tiejiangyingzi basin. It can be concluded that andesite volcanic rocks distributed in the Tiejiangyingzi basin were formed in an extensional tectonic environment during the Mesozoic orogen, and the lower crust had experienced extensive high‐temperature metamorphism and melting. This gold‐bearing lower crust is closely related to mineralization. Therefore, the conclusions of this research have an important implication for further prospecting in southeastern Chifeng, China. 相似文献
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宁芜盆地凹山和东山铁矿床中阳起石的激光39Ar-40Ar年代学研究 总被引：6，自引：1，他引：5
文章通过对凹山和东山铁矿床中特征的组合矿物之一伟晶状阳起石进行激光39Ar-40Ar法定年,精确测定了玢岩铁矿的成矿时代。其中东山铁矿中新鲜阳起石(黑绿色)的39Ar-40Ar等时线年龄在126～129Ma之间,与赋矿围岩大王山组火山岩中角闪石的等时线年龄(127Ma)一致,证明成矿与成岩密切相关,成矿与成岩是同时期的产物。而凹山铁矿中蚀变阳起石(灰绿色)的39Ar-40Ar等时线年龄为(114±16)Ma。2种阳起石分别形成于成矿作用的不同阶段,黑绿色新鲜阳起石与磷灰石、磁铁矿同期形成,形成于岩浆向热液演化的高温阶段,在成岩和成矿之后的冷却过程中,矿体和潜火山岩体具有相同的闪石封闭温度(500℃±);而灰绿色蚀变阳起石形成于中期阳起石(透辉石)-钠长石-磷灰石-磁铁矿化矿体围岩蚀变阶段。 相似文献
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大别造山带南部宿松球颗结构安山岩的球颗结构指示此安山岩是喷发于水下环境。球颗由放射状斜长石（蚀变为钠长石和更长石）及少量位于斜长石间隙的单斜辉石、普通角闪石和蚀变矿物石英组成，基质由玻璃质、绿泥石、黝帘石、角闪石组成，SiO2=56.17%-58.31%,AI2O3=14.08% -14.67%,TiO2=0.91%-0.94%,NaO=4.19%-4.58%,K2O=0.93%-1.42%,MgO含量高达5.66%-6.98%,100Mg/(Mg Fe)=64.1-66.2。球颗结构安山岩和闪长斑岩、英安岩均为亚碱性的钙碱性系列岩石。球颗结构安山岩富集Si(1259-1588μg/g）、Ba(880-1134μg/g）、Th、Rb等大离子亲石元素。大离子亲石元素相对高场强元素富集，例如La/Nb=5.56-6.07。高场强元素的比值具有类似MORB特性，例如Zr/Nb=22.08-26.14,Hf/Ta=5.62-9.62.亏损Ta、Nb、P、Ti等高场强元素，自Ce元素向右，各元素的含量下降很快，表现出活动大陆边缘的与俯冲作用有关的火山岩的特征。轻稀土元素强烈富集，稀土分馏显著（La/Yb)N=32.84，没有Eu异常。具有岛孤安山岩的特性，但有异常高的(La-Yb)N=28.63-26.74,(La/Y)N=70.33-81.04。并且Y和Yb元素有显著的亏损，Y＜20μg/g，YN=2.74-2.86,YbN=2.18-2.35.从La-(La/Sm)图解看，本安山岩为部分熔融作用的产物。La/Nb的平均值为5．83，这在岛弧火山岩是很广泛的特点。Nd的εNd(0)为－18．71～－19．16，物源是大陆物质或被大陆物质所混染。Nd模式年龄为1．9Ga，可能反映了Nd模式年龄为1．7Ga的俯冲扬子板引起Nd模式年龄为2．5Ga的华北大陆岩石圈地幔楔物质部分熔融，产生这种玄武质岩浆。因而具有大陆基底的活动大陆边缘的岛弧火山岩的地球化学特征。 相似文献
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Assessment of rockfall hazard around Afyon Castle,Turkey 总被引：2，自引：0，他引：2
The Afyon Castle is a tourist destination and a historical site in the City of Afyon in Turkey. The Castle is located on a
steep hill, with a height of 226 m. In close proximity to the Castle there are settlements. The hill consists of trachitic
andesite. The rock contains columnar joints and flow layering. Owing to these discontinuities, blocks of varying sizes had
fallen down. The settlement areas near the Castle are now in danger because of the rockfall risk. In this study, rockfall
analysis was carried out along nine profiles of the hill. Fall-out distance, bounce height, kinetic energy and velocity of
the rocks along each profile were investigated. The results of the analyses were evaluated, and the areas delineated as susceptible
to rockfall risk are highlighted. Remedial measures including rock bolts and protective fences were suggested on the basis
of the field observations and the rockfall risk evaluation. 相似文献
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The stone pagoda of the Bunhwangsa temple in Republic of Korea was made of piling small brick-shaped stones. The majority
of stone bricks are andesitic rocks with variable geneses. Rock properties of the pagoda roof suffer partial significant deterioration,
such as multiple peel-offs, exfoliation, onion-peel-like decomposition, cracks forming round lines and falling-off stone pieces.
The stylobates and tabernacles at the four corners are composed of granitic rocks, which are heavily contaminated by lichens
and mosses. Some of these contamination marks show dark black or yellowish brown colors by inorganic secondary hydrates. The
four tabernacles and northern face of the pagoda body have been exposed to relatively high humidity, which causes light gray
efflorescence as stalactites between the northern and western sides of the body. The efflorescences are composed of calcite,
gypsum and clay minerals. The stone lion statues at the southeast and northeast corners are made of alkali granite, while
the others are lithic tuff. Total rock properties of the pagoda consist of 9,708 stone bricks. Among them, 11.0% are fractured,
6.7% are fallen off, and 7.0% show considerable surface efflorescence, which shows that the pagoda has been highly deteriorated
by physical, chemical and biological weathering. The authors strongly suggest long-term monitoring and comprehensive conservation
researches. 相似文献