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31.
房山花岗岩岩体氧氢碳的同位素研究 总被引:1,自引:0,他引:1
测定了房山花岗岩侵入体的岩石、共生矿物和气液包体的氧、氢、碳的同位素组成。共生石英-黑云母和石英-全岩的δ~(18)O数据表明,房山花岗岩侵入体保存了氧同位素平衡,氧同位素温度在450—580℃之间。大多数共生黑云母-角闪石δD值的相关性基本上符合Suzuoki-Epstein关系式,可以认为房山侵入体也保存了氢同位素平衡,推算得到的岩浆流体的δD值在-70—-30之间。气液包体中CO_2的δ(13)C为-4—-8,属于一种深源碳,可以利用地下水参加岩浆后期演化的假定来解释黑云母二长闪长岩氢、碳同位素异常 相似文献
32.
江西西华山脉钨矿床的形成与含钨花岗岩浆演化密切相关,“附加侵入”二云母或白云母碱性长石花岗岩的出现,对脉钨矿床的形成具有重要意义。脉钨矿床形成的全过程可概况为:从深熔—重熔花岗质岩浆产生→岩浆不断的分异并多次上侵→含钨岩浆的结晶分异(主侵入成岩)→碱质自交代→低熔岩浆的形成和气热分馏(附加侵入成岩)→细晶岩等的贯入和成矿流体最后从岩浆中彻底分离→成矿流体上升充填交代及其性质的演变→黑钨矿(长石)石英脉的形成。 相似文献
33.
以湖南宏厦桥花岗岩体作为研究区,对地下水化学分析资料进行了研究,发现区内地下水系超淡、极软的、弱-中性的重碳酸型水,其化学组成以Ca2 、Mg2 、K 、Na 、HCO3-为主。与株洲地区的地下水相比,可溶性S iO2、K 、Na 和游离CO2明显偏高,而且,在水中M g2 、K 、Na 、HCO3-所占比重更大,m eq%平均比值分别是株洲地区地下水的2.23、1.27、1.16倍,表现出典型的花岗岩地区地下水相应的化学组成。研究还发现,区内地下水化学的分布具有较强的水平分带性。研究认为:区内地下水化学的形成和迁移受岩性、大气降水及影响水交替强度的地形、地貌、地表水系、断裂构造的控制,同时受其他气候要素及植被、人类活动等生物作用的影响;区内地下水化学成分的形成以硅酸盐矿物的分解和水解等化学风化作用为主,风化过程中CO2的积极参与起作关键性的促进作用。同时水中CO2的减少和阴离子以HCO3-离子占绝对优势地位,进一步说明花岗岩的化学风化过程是一个净碳汇的过程。 相似文献
34.
Fukun Chen Xiang-Hui Li Xiu-Li Wang Qiu-Li Li Wolfgang Siebel 《International Journal of Earth Sciences》2007,96(6):1179-1194
The Baoshan block of the Tethyan Yunnan, southwestern China, is considered as northern part of the Sibumasu microcontinent.
Basement of this block that comprises presumably greenschist-facies Neoproterozoic metamorphic rocks is covered by Paleozoic
to Mesozoic low-grade metamorphic sedimentary rocks. This study presents zircon ages and Nd–Hf isotopic composition of granites
generated from crustal reworking to reveal geochemical feature of the underlying basement. Dating results obtained using the
single zircon U–Pb isotopic dilution method show that granites exposed in the study area formed in early Paleozoic (about
470 Ma; Pingdajie granite) and in late Yanshanian (about 78–61 Ma, Late Cretaceous to Early Tertiary; Huataolin granite).
The early Paleozoic granite contains Archean to Mesoproterozoic inherited zircons and the late Yanshanian granite contains
late Proterozoic to early Paleozoic zircon cores. Both granites have similar geochemical and Nd–Hf isotopic charateristics,
indicating similar magma sources. They have whole-rock T
DM(Nd) values of around 2,000 Ma and zircon T
DM(Hf) values clustering around 1,900–1,800 and 1,600–1,400 Ma. The Nd–Hf isotopic data imply Paleoproterozoic to Mesoproterozoic
crustal material as the major components of the underlying basement, being consistent with a derivation from Archean and Paleoproterozoic
terrains of India or NW Australia. Both granites formed in two different tectonic events similarly originated from intra-crustal
reworking. Temporally, the late Yanshanian magmatism is probably related to the closure of the Neotethys ocean. The early
Paleozoic magmatism traced in the Baoshan block indicates a comparable history of the basements during early Paleozoic between
the SE Asia and the western Tethyan belt, such as the basement outcrops in the Alpine belt and probably in the European Variscides
that are considered as continental blocks drifting from Gondwana prior to or simultaneously with those of the SE Asia. 相似文献
35.
36.
对本省钽铌矿床根据矿床成因采取四级划分原则进行了详细分类,按成矿作用分内生矿床和外生矿床二大类,按矿床成因及成矿地质条件分二个亚类,根据成矿阶段分七种矿床类型,根据与矿化有关的母岩体的标型矿物分十四种矿体类型,其中蚀变的花岗岩型钽铌矿床是主要类型,其次是伟晶岩型钽铌矿床,细晶岩型矿床因矿物细小,目前尚难利用.各种类型钽铌矿床(点)主要是位于构造隆起带内,分布于怀玉山、武功山、武夷山、于山和九岭等5个钽铌成矿带中.从华力西期至燕山期均有产出,其中以燕山中期为主要成矿期. 相似文献
37.
38.
Micro-sheeting of granite and its relationship with landsliding specifically after the heavy rainstorm in June 1999, Hiroshima Prefecture, Japan 总被引:1,自引:0,他引:1
M. Chigira 《Engineering Geology》2001,59(3-4):219-231
Certain types of granite in mountainous areas are microscopically sheeted to a depth of 50 m due to unloading under the stress field that reflects slope morphology. Micro-sheets generally strike parallel to major slope surfaces and gently dip downslope, forming cataclinal overdip slopes. The cataclinal overdip slope accelerates creep movement of micro-sheeted granite, which in turn loosens and disintegrates granite via the widening or neoformation of cracks, probably in combination with stress release, temperature change, and changes in water content near the ground surface. The surface portion of micro-sheeted granite is thus loosened with a well-defined basal front, which finally slides in response to heavy rain. Innumerable landslides of this type occurred in Hiroshima Prefecture, western Japan, following the heavy rainstorm of 29 June 1999. Following such landslides, the weathering of micro-sheeted granite exposed on the landslide scar recommences, setting the stage for future landslide. 相似文献
39.
CHIME age dating of monazites from metamorphic rocks and granitic rocks of the Ryoke belt in the Iwakuni area, Southwest Japan 总被引:2,自引:0,他引:2
Abstract CHIME (chemical Th-U-total Pb isochron method) ages were determined for monazite from gneisses and granitoids of the Ryoke belt in the Iwakuni area. The CHIME monazite ages are 99.6 ± 2.4, 98.9 ± 2.1 and 98.2 ± 5.7 Ma for the Ryoke gneiss, 90.7 ± 2.2, 89.7 ± 2.0 and 89.3 ± 2.2 Ma for the Tajiri Granite, 91.0 ± 3.2, 90.6 ± 3.2 and 89.9 ± 3.2 Ma for the Namera Granite, 89.3 ±3.3 and 88.6 ± 5.6 Ma for a small stock at Shimizu, and 87.3 ± 1.6 and 86.6 ± 2.1 Ma for the post-tectonic Shimokuhara Granite. The CHIME monazite ages, interpreted as the time of the first attainment at the amphibolite facies conditions for the gneisses and as the time of emplacement for the granites, respectively, agree with the field intrusive sequence. The present dating documented that the Ryoke metamorphism in the Iwakuni area reached the amphibolite facies conditions at ∼98 Ma, was complete at -87 Ma, the time of emplacement of the post-tectonic Shimokuhara Granite. 相似文献
40.