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931.
The Jinman Cu deposit is hosted in sandstones and slates of the Jurassic Huakaizuo Formation in the Mesozoic to Cenozoic Lanping
basin in western Yunnan, China. Despite the fact that Cu mineralization occurs mainly in quartz–carbonate veins controlled
by faults and fractures, the Jinman deposit was classified as a sediment-hosted stratiform Cu deposit, mainly because it is
hosted in a sedimentary basin characterized by abundant red beds with many stratiform Cu deposits. A detailed petrographic
and microthermometric study of fluid inclusions from the Jinman deposit reveals the presence of abundant CO2-rich fluid inclusions, together with aqueous inclusions. The CO2-rich inclusions have CO2 melting temperatures mainly from −58.0°C to −56.6°C, homogenization temperatures of the carbonic phase (mostly into the liquid
phase) mainly between 22°C and 30°C, clathrate melting temperatures from 1.8°C to 9.2°C, with corresponding salinities from
1.6 to 13.4 wt.% NaCl equivalent, and total homogenization temperatures from 226°C to 330°C. The aqueous inclusions have first
melting temperatures from −60°C to −52°C, ice melting temperatures from −41.4°C to −2.3°C, with salinities from 3.9 to 29.0 wt.%
NaCl equivalent, and total homogenization temperatures mainly from 140°C to 250°C. These fluid inclusion characteristics are
comparable to those of orogenic or magmatic mineralization systems and are uncharacteristic of basinal mineralization systems,
suggesting that it is inappropriate to classify the Jinman deposit as a sediment-hosted stratiform Cu deposit. The results
of this study, together with geochemical data reported previously, suggest that the Jinman deposit formed in a hydrothermal
system that involved both extra-basinal, deeply sourced CO2-rich fluid and basinal, aqueous fluid. 相似文献
932.
Mapping lithospheric boundaries using Os isotopes of mantle xenoliths: An example from the North China Craton 总被引:5,自引:0,他引:5
Jingao Liu Roberta L. Rudnick Shan Gao Philip M. Piccoli Wen-liang Xu 《Geochimica et cosmochimica acta》2011,75(13):3881-6182
The petrology, mineral compositions, whole rock major/trace element concentrations, including highly siderophile elements, and Re-Os isotopes of 99 peridotite xenoliths from the central North China Craton were determined in order to constrain the structure and evolution of the deep lithosphere. Samples from seven Early Cretaceous-Tertiary volcanic centers display distinct geochemical characteristics from north to south. Peridotites from the northern section are generally more fertile (e.g., Al2O3 = 0.9-4.0%) than those from the south (e.g., Al2O3 = 0.2-2.2%), and have maximum whole-rock Re-depletion Os model ages (TRD) of ∼1.8 Ga suggesting their coeval formation in the latest Paleoproterozoic. By contrast, peridotites from the south have maximum TRD model ages that span the Archean-Proterozoic boundary (2.1-2.5 Ga). Peridotites with model ages from both groups are found at Fansi, the southernmost locality in the northern group, which likely marks a lithospheric boundary. The Neoarchean age of the lithospheric mantle in the southern section matches that of the overlying crust and likely reflects the time of amalgamation of the North China Craton via collision between the Eastern and Western blocks. The Late Paleoproterozoic (∼1.8 Ga) lithospheric mantle beneath the northern section is significantly younger than the overlying Archean crust, indicating that the original lithospheric mantle was replaced in this region, either during a major north-south continent-continent collision that occurred during assembly of the Columbia supercontinent at ∼1.8-1.9 Ga, or from extrusion of ∼1.9 Ga lithosphere from the Khondalite Belt beneath the northern Trans-North China Orogen, during the ∼1.85 Ga continental collision between Eastern and Western blocks. Post-Cretaceous heating of the southern section is indicated by high temperatures (>1000 °C) recorded in peridotites from the 4 Ma Hebi suite, which are significantly higher than the temperatures recorded in peridotites from the nearby Early Cretaceous Fushan suite (<720 °C), and likely reflects significant lithospheric thinning after the Early Cretaceous. Combining previous Os isotope results on mantle xenoliths from the eastern North China Craton with our new data, it appears that lithospheric thinning and replacement may have evolved from east to west with time, commencing before the Triassic on the eastern edge of the craton, occurring during the Jurassic-Cretaceous within the interior, and post-dating 125 Ma on the westernmost boundary. 相似文献
933.
秦岭晚中生代花岗岩时空分布、成因演变及构造意义 总被引:34,自引:14,他引:20
秦岭晚中生代花岗岩主要发育于秦岭北部的华北地块南缘和北秦岭,南秦岭仅有零星出露。本文报道了3个晚中生代大岩体的年代学和其中2个岩体的地球化学和同位素数据,并系统收集了发表的相关资料,对秦岭晚中生代花岗岩进行了初步总结。华北地块南缘蓝田花岗岩的锆石LA-ICPMS U-Pb年龄为133±1Ma, εNd(t)=-11.8~-18.3, 锆石εHf(t)=-37.7~-5.7。 北秦岭构造带中牧护关花岗岩的锆石LA-ICPMS U-Pb年龄为 150±1Ma, εNd(t)=-7.6~-11.4, 锆石εHf(t)=-7.3~-17.4;蟒岭花岗岩的锆石SHRIMP U-Pb年龄为149±2 Ma。 依据收集到的26个锆石U-Pb和3个黑云母Ar-Ar年代学资料, 秦岭晚中生代花岗岩浆的演化可分为2个阶段:第一阶段为160~130Ma(晚侏罗世-早白垩世), 以I-型花岗岩为主, 主要发育于华北地块南缘和北秦岭,在南秦岭仅零星分布;第二阶段为120~100Ma(早白垩世中晚期), 以I-A过渡型和A-型花岗岩为主,主要分布在华北地块南缘的东部和北秦岭,出露面积比第一阶段小。第一阶段(160~130Ma)花岗岩主要形成于古老地壳物质的部分熔融,并有年轻幔源组分的参与,形成于挤压向伸展转换的构造环境。第二阶段(120~100Ma)花岗岩的形成除了古老地壳物质的部分熔融外,有更多的年轻幔源组分加入,发育于陆内伸展环境。花岗岩的同位素特征显示,从华北地块南缘到南秦岭,底基物质中年轻组分有增加的趋势,花岗岩的物源受深部地壳物质组成特征的控制。 相似文献
934.
北山辉铜山泥盆纪钾长花岗岩锆石U-Pb年龄、 成因及构造意义 总被引:6,自引:5,他引:1
LA-ICP-MS锆石U-Pb定年结果表明,北山柳园地区辉铜山钾长花岗岩的形成年龄为397±3Ma (MSWD=1.1).地球化学特征显示为高钾钙碱性的高分异Ⅰ型花岗岩到A型花岗岩过渡的特征.其全岩εNd(t)值为-1.3~ +1.2,Nd模式年龄(tDM)为960 ~ 1530Ma;锆石εHf(t)值为-1.0~ +5.8,两阶段Hf模式年龄(tDM2)为1024~1455Ma.地质背景、地球化学和同位素综合分析显示,辉铜山岩体为造山后伸展拉张背景下,幔源岩浆底侵导致上覆年轻地壳(可能为洋壳、岛弧建造或增生楔物质)部分熔融形成的钙碱性花岗闪长质岩浆经进一步演化及结晶分异形成.北山南带地区早-中泥盆世花岗岩显示出高分异钙碱性Ⅰ型花岗岩、I-A型花岗岩和A型花岗岩的组合特征.因此,在397Ma左右,北山地区古生代岩浆已经从Ⅰ型或S型转化为I-A型特征,构造环境转化为后造山或同造山晚期的伸展环境. 相似文献
935.
936.
天然半导体矿物金红石因结构中含有类质同象替代杂质元素V和Fe,具有一定的可见光吸收和光催化活性。为改善金红石的日光光催化性能,在H2还原气氛下,对天然金红石粉末进行500~900℃不同温度的热处理改性研究。紫外-可见漫反射吸收光谱(UV-Vis diffuse reflectance absorption spectra)表明H2还原处理显著改善了金红石在可见光区460~750 nm波段的光吸收,其中900℃处理样品的光吸收提升最为明显。电子顺磁共振(EPR)和X射线光电子能谱(XPS)测试表明,随着还原温度升高,杂质元素V和Fe从高价态(V5+,Fe3+)向较低的价态(V4+,V3+,Fe2+)转化,同时金红石表面的化学吸附水含量也有所增加。本文认为H2还原热处理引起的过渡金属元素价态的改变,尤其是较低氧化态V离子(V4+和V3+)的形成,可能是导致金红石样品可见光吸收显著增加的主要原因。 相似文献
937.
During the past five decades, fluctuations of glaciers were reconstructed from historical documents, aerial photographs, and remote sensing data. From 1956 to 2003, 910 glaciers investigated had reduced in area by 21.7% of the 1956 value, with a mean reduction for the individual glacier of 0.10 km2. The relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than la... 相似文献
938.
939.
对研究区变质岩的岩石学、地球化学研究表明,金水口群中-深变质岩原岩的为一套以火山岩为主的火山-沉积组合。火山岩主要为晶屑凝灰岩、岩屑凝灰岩、角砾凝灰岩、凝灰质砂岩等,属钙碱性岩系。沉积岩为泥灰岩。火山岩构造环境应属活动大陆边缘。 相似文献
940.