17 results on '"Wang, Qingchen"'
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2. Geochemical evidence for submarine hydrothermal origin of the Middle-Upper Permian chert in Laibin of Guangxi, China
- Author
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Qiu, Zhen and Wang, QingChen
- Published
- 2011
- Full Text
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3. Environmental Redox Changes of the Ancient Sea in the Yangtze Area during the Ordo-Silurian Transition
- Author
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Chu Yang, Chen Daizhao, Wang Jian-guo, Wang Qingchen, and Yan Detian
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chemistry.chemical_classification ,Total organic carbon ,Geochemistry ,Halocline ,Geology ,engineering.material ,Anoxic waters ,Sedimentary depositional environment ,Oceanography ,Water column ,chemistry ,engineering ,Organic matter ,Pyrite ,Sea level - Abstract
Extensive organic-matter (OM) rich facies (black shales) occur in the Ordo-Silurian boundary successions in the Yangtze area, South China. To investigate the redox changes of the Yangtze Sea during the Ordo-Silurian transition, two OM sections (Wangjiawan in Yichang, Hubei Province, and Sanjiaguan in Zhangjiajie, Hunan Province) straddling the Ordo-Silurian boundary are studied. The measurements finished in this study include contents of the total organic carbon (TOC), pyrite sulphur, and different species of Fe, including dithionite-extractable Fe (FeD), pyrite Fe (FeP), HCI-extractable Fe (FeH), and total Fe (FeT), in black shales, as well as other redox proxies, such as the S/C ratio, the ratio between highly reactive Fe (FeHR = FeD + FeP) and FeT, and the Fep/(FeP + FeH) ratio, known as the degree of pyritization (DOP). In the Wangjiawan section, the Middle Ashgill sediments have high FeHR/FeT ratios (0.20-0.77; avg. 0.45), high DOP values (0.21-0.72; avg. 0.54), and a relatively constant sulfur content independent of the organic carbon content. By the contrast, the mid-early Hirnantian deposits generally have low FeHR/FeT ratios (0.10-0.35; avg. 0.21), low DOP values (0.11-0.40; avg. 0.28), and S/C values are clustering on the normal marine value (S/C = 0.36). The late Hirnantian and early Rhuddanian deposits, similar to those of the Middle Ashgill deposits, are characterized by high FeHR/FeT ratios (0.32-0.49; avg. 0.41), high DOP values (0.46-0.68; avg. 0.53) and fairly constant sulfur contents. These data suggest the occurrences of marine anoxia on the Yangtze Sea shelf during intervals of the Mid Ashgill, Late Hirnantian and Early Rhuddanian, and ventilated and oxygenated marine conditions during the mid-early Hirnantian time. The mid-early Hirnantian ventilated event was concomitant with the global glacial period, likely resulted from the glacio-eustatic sea-level fall and subsequent circulation of cold, dense oxygenated waters upon the shelf seabed. Accordingly, the abrupt change from oxygenated to anoxic marine waters from the late Hirnantian and the early Rhuddanian were resulted from the post-glacial rise of eustatic sea level. Combined with the data from Sanjiaguan section near the subemergent highland, salinity stratification of water columns are strongly evidenced by very low S/C ratios (0.00-0.08, avg. 0.02), low FeHR/FeT ratios (0.10-0.37, avg. 0.27), low DOP values (0.01-0.27, avg. 0.10), and TOC contents (0.72%-4.27%, avg. 2.55%). Under this circumstance, the anoxic water columns could have formed beneath the halocline, above which desalinized waters formed. In the Wangjiawan section, TOC contents are generally high (0.94-9.32%, avg. 4.44%), but low (0.35%-2.12%, avg. 1.29%) in the mid-early Hirnantian that is coincident with the oceanic oxic stage, together with relation of the organic contents to the stratal thickness, suggesting that the accumulation of the organic matter was mainly controlled by the oxygen levels of the water columns; on the other hand, productivity and depositional rate may also have played a role in the organic accumulation and preservation.
- Published
- 2010
4. New Data Regarding Hotly Debated Topics Concerning UHP Metamorphism of the Dabie-Sulu Belt, East-Central China
- Author
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Wang Qingchen, Zhai Mingguo, and Cong Bolin
- Subjects
Recrystallization (geology) ,Subduction ,Mantle wedge ,Oceanic crust ,Lithosphere ,Metamorphic rock ,Geochemistry ,Metamorphism ,Geology ,Eclogite - Abstract
Critical but controversial problems in the study of UHP metamorphic rocks from the Dabie-Sulu region include: (1) the possible existence of ophiolitic melange; (2) the “in situ” versus “foreign” origin of UHP eclogites and their enclosing gneisses; (3) the possible presence and role of fluids during ultrahigh-pressure (UHP) recrystallization; (4) the timing of collision between the Yangtze and Sino-Korean continental blocks; (5) the polarity of syncollisional subduction; and (6) a single-versus multistage exhumation scenario for the UHP rocks. These questions are discussed in light of new geological, geochemical, and isotopic constraints. Our conclusions for the Dabie-Sulu belt are as follows: (1) Mafic-ultramafic blocks are of two distinct origins: one group samples lithosphere of the suprasubductionzone mantle wedge, whereas the second group represents postcollisional magmatic intrusions. Neither lithologic group represents true oceanic crust. (2) Quartzofeldspathic gneisses enveloping the eclogites are...
- Published
- 1999
5. Structural coupling of the Dabie Orogen with Hefei Basin
- Author
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Ma Li, Wang Qingchen, and Cong Bolin
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Structural coupling ,Multidisciplinary ,Inversion (geology) ,Geochemistry ,Orogeny ,Mesozoic ,Structural basin ,Geomorphology ,Mantle (geology) ,Geology - Abstract
Geological, geophysical and geochemical data show that both of the Dabie Orogen and Hefei Basin formed during a Mesozoic orogeny. A three-stage development of the Hefei Basin includes down-warping, half grabben, and positive inversion. Both the uplift in orogen and the depression in basin resulted from the “de-rooting” of orogen and up-welling of the mantle.
- Published
- 1997
6. Top boundary of the Dabie UHPM rocks, central China
- Author
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Cong Bolin, Liu Xiaohan, Wang Qingchen, and Shigenori Maruyama
- Subjects
Felsic ,Metamorphic rock ,Geochemistry ,Feldspar ,Shear (geology) ,visual_art ,Earth and Planetary Sciences (miscellaneous) ,visual_art.visual_art_medium ,General Earth and Planetary Sciences ,Clockwise ,Shear zone ,Quartz ,Geology ,General Environmental Science ,Gneiss - Abstract
The top boundary of the ultra-high pressure metamorphic (UHPM) rocks in the Dabie Mountains, central China, has been mapped. The results show that the top boundary of the UHPM rocks is occupied by flat-lying felsic gneiss, on which tonalitic gneiss rests. Petrological and mineralogical evidence indicates a wide P-T gap across the boundary with an estimated peak metamorphic P-T value of the UHPM rocks being >30 kbar and 800 ± 50°C, and that of the tonalitic gneiss around 11 kbar and 800°C. Their P-T-t paths are different. The former has a clockwise path and the latter is counterclockwise. This implies that the UHPM rocks at the bottom and the tonalitic gneiss on top have been structurally juxtaposed together. The top boundary, i.e. the contact between the UHPM rocks and tonalitic gneiss, shows characteristics of a ductile shear zone. Microscopically, feldspar and quartz in the shear zone are characterized by ductile deformation. In larger scale, the top boundary is undulating. Shear sense in the top boundary is a two-way direction. Only the latest shear sense measured with c -axes of quartz show a consistent direction of top-to-the-north. The study provides some constraints to the exhumation process of the Dabie UHPM rocks.
- Published
- 1995
7. Petrogenesis of ultrahigh-pressure rocks and their country rocks at Shuanghe in Dabieshan, Central China
- Author
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Zhao Zhongyan Zhao Zhongyan, Wang Qingchen, Zhai Mingguo, Brian F. Windley, R. N. Wilson, Dennis A. Carswell, and Cong Bolin
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Geochemistry and Petrology ,Geochemistry ,Central china ,Geology ,Petrogenesis - Published
- 1995
8. Petrological-tectonic units in the coesite-bearing metamorphic terrain of the Dabie Mountains, central China and their geotectonic implications
- Author
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Zhai Mingguo, Wang Qingchen, Zhao Zhongyan Zhao Zhongyan, Cong Bolin, Wang Gang, and Jiang Laili
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Metamorphic rock ,Geochemistry ,Metamorphism ,Granulite ,Basement (geology) ,Earth and Planetary Sciences (miscellaneous) ,General Earth and Planetary Sciences ,Shear zone ,Eclogite ,Geomorphology ,Geology ,Metamorphic facies ,General Environmental Science ,Gneiss - Abstract
Four main faults outline the metamorphic terrain in the Dabie Mountains, central China. The difference of metamorphic grade in the northern, central and southern parts is well-established. This study suggests that these metamorphic rocks belong to three individual geological-tectonic units, which are the northern Andean-type magmatic arc, the central UHPM rock-bearing melange zone and the mobilized sedimentary cover and basement of Yangtze southern continental margin. An old ductile sheared zone through Wuhe and the south of Yuexi-Shuihou divides the Dabie metamorphic complex into northern and central units. The northern unit is predominantly occupied by tonalitic-trondhjemitic grey gneisses and amphibolites facies metasediments. Several approximately E-W-trending ductile-sheared mylonitic belts cut through the grey gneisses, and are especially developed in the northern and southern margins of the unit (high-strain zones). There is a series of lenses of basic granulites, serpentinites and Grt-pyroxenites in the high-strain zones. They do not have the petrological and geochemical characteristics of ophiolitic rocks. However, they may represent the root of an arc combined with grey gneisses. Our study also demonstrates that all rocks from the northern block did not undergo eclogite facies metamorphism. Mesozoic post-collisional granites occur extensively in the Dabie terrain, especially in the northern unit. Coesite and diamond-bearing eclogites in the central unit indicate a regional ultra-high-pressure metamorphism of pressures of > 30 kbar and temperature of 600–800°C. Except for eclogites, various ultra-high-pressure metamorphic (UHPM) rocks include ultramafic rocks, marbles and other metamorphosed sedimentary rocks. They, as large-scale blocks, are mixed with lower P-T encompassing host rock orthogneisses. The central block is a UHPM rock-bearing melange zone. The south block is a metasedimentary sequence of continental margin of the Yangtze plate. The boundary between the central and southern blocks is located in the north from Huangzhen, extending eastwards through the dam of Huangliangting reservoir. In addition, the Foziling Group, north of the Dabieshan terrain was possibly deposited in an extensional basin on an extensional shear zone, comparable to the basin in the Variscan of France and the Caledonides of S. Norway (Dewey, Ryan and Anderson, Geological Society Special Publication No. 76, pp. 325–343, 1993). The authors hope that this information will provide more valid evidence of regional tectonic evolution.
- Published
- 1995
9. The Northern Dabieshan Terrain: A Possible Andean-Type Arc
- Author
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Wang Qingchen, Zhang Qi, Cong Bolin, and Zhai Mingguo
- Subjects
Arc (geometry) ,Back-arc basin ,Metamorphic rock ,Geochemistry ,Geology ,Terrain ,Petrology ,Gneiss - Abstract
The northern Dabieshan metamorphic terrain (NDT) is an analogue of an Andean-type magmatic arc. The predominant rock type is a trondhjemitic-tonalitic-granodioritic (TTG) gneiss with bodies of meta...
- Published
- 1994
10. Ultra-high pressure metamorphic rocks in the Dabie-Su-Lu region, China: Their formation and exhumation
- Author
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Cong Bolin, Wang Qingchen, Zhang Ruyuan, Zhao Zhongyan Zhao Zhongyan, Zhai Mingguo, and Ye Kai
- Subjects
Blueschist ,Metamorphic rock ,Geochemistry ,Metamorphism ,Geology ,Eclogite ,Petrology ,Granulite ,Protolith ,Metamorphic facies ,Gneiss - Abstract
Based on petrological, structural, geological and geochronological research, the authors summarize the progress of ultra-high pressure (UHP) metamorphic rock study since 1989 by Chinese geoscientists and foreign geoscientists in the Dabie-Su-Lu region. The authors introduce and discuss a two-stage exhumation process for the UHP metamorphic rocks that have various lithologies; eclogite, ultramafics, jadeitic quartzite, gneiss, schist and marble. The metamorphic history of UHP metamorphic rocks is divided into three stages, that is, the pre-eclogite stage, coesite eclogite stage, and retrograde stage. Prior to UHP metamorphism, the ultramafics had a high temperature environment assemblage of mantle and others had blueschist facies assemblages. The granulite facies assemblages, which have recorded a temperature increase event with decompression, have developed locally in the Weihai basaltic rocks. Isotopic ages show a long range from > 700 Ma to 200 Ma. The diversity in protoliths of UHP metamorphic rocks may be related to the variation of isotopic ages older than 400 Ma. The Sm-Nd dating of ~ 220 Ma could reflect the initial exhumation stage after the peak UHP metamorphism in relation to the collision between the Sino-Korean and Yangtze blocks and subsequent events. Petrological and structural evidence imply a two-stage exhumation process. During the initial exhumation, the UHP metamorphic rocks were sheared and squeezed up in a high P/T regime. In the second exhumation stage the UHP metamorphic rocks were uplifted and eventually exposed with middle crustal rocks.
- Published
- 1994
11. Coesite-bearing granulite retrograded from eclogite in Weihai, eastern China
- Author
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Zhai Mingguo, Takao Hirajima, Nobuki Hiramatsu, Cong Bolin, Li Jiaju Li Jiaju, Zhao Zhongyan Zhao Zhongyan, Wang Qingchen, Masaki Enami, and Akira Ishiwatari
- Subjects
Albite ,Geochemistry and Petrology ,Coesite ,engineering ,Geochemistry ,Plagioclase ,Epidote ,engineering.material ,Eclogite ,Omphacite ,Granulite ,Geology ,Hornblende - Abstract
Coesite in a granulite host-rock is reported from Weihai City, northeastern Shandong Province, China. Coesite occurs as inclusions in garnet, which is separated from the fine-grained matrix of quartz + clinopyroxene + homblende by a zoned corona of plagioclase + clinopyroxene + orthopyroxene + hornblende. Petrological evidence shows that the coesite-bearing granulite is retrograded from eclogite. Three stages in the metamorphic history of the granulite have been recognized. (i) Coesite-eclogite stage: The assemblage reconstructed from the inclusions in garnet is Mg-rich garnet + omphacite + coesite + rutile. (ii) During the granulite stage, these minerals reacted to form quartz + clinopyroxene + hornblende (in the matrix), clinopyroxene + albite (omphacite pseudomorphs) and plagioclase + clinopyroxene + orthopyroxene + hornblende (as corona around garnet). (iii) Amphibolite stage: Earlier minerals were replaced by biotite, epidote and hornblende. The P-T conditions estimated with various geothermobarometers show a T-increasing and P-decreasing path from the eclogite stage (T ∼ 720°C, P > 28 kbar) to the granulite stage (T ∼ 850°C, P ∼ 10 kbar). Thus the exhumation of the ultra-high-pressure rocks in Weihai proceeded under increasing temperature, and may not have been as fast as it was thought before
- Published
- 1993
12. Geodynamics of UHP-rock-bearing continental collision zone in central China
- Author
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Cong Bolin, Wang Qingchen, and Zhu Rixiang
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Bearing (mechanical) ,Continental collision ,law ,Earth science ,Geochemistry ,Central china ,Geodynamics ,Geology ,law.invention - Published
- 1998
13. Recent developments in study of the typical superimposed basins and petroleum accumulation in China: Exemplified by the Tarim Basin
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Wang Qingchen and Jin Zhijun
- Subjects
geography ,geography.geographical_feature_category ,Geochemistry ,Structural basin ,Sedimentary basin ,Sedimentary depositional environment ,Tectonics ,Source rock ,Basin modelling ,Sedimentary basin analysis ,General Earth and Planetary Sciences ,Sedimentary rock ,Geomorphology ,Geology - Abstract
Most of petroliferous sedimentary basins in China have experienced multiple phases of tectonic evolution and deposition, and are characterized by tectonic and depositional superimposition. The term “superimposed basin” is suggested to describe those basins which consist of two or more simple prototype basins superimposing vertically and/or coalescing laterally. The characteristics of petroliferous superimposed basins are “multiple stages of basin forming and reworking, multiple layers of source rocks, multiple periods of hydrocarbon generation and expulsion, multiple periods of petroleum migration-accumulation-escape”. Therefore, applying the wave process analysis method to studying the process of basin formation, hydrocarbon generation, and reservoir formation, and then establishing theory of “petroleum accumulation system” is helpful to enhancing petroleum exploration efficiency in superimposed basins. This paper will, based on case study in the Tarim basin, report the major developments in studying basin formation, hydrocarbon generation and petroleum accumulation. In study of basin formation, (1) geophysical comprehensive profiles reveal that the Tarim plate has been subducted beneath the Tianshan orogenic belt with an interfinger structure and that the deep structure in the eastern section of the Tianshan orogenic belt is different from that in the western section. (2) The vertical variation in debris and geochemical composition reveals the nature and Mesozoic-Cenozoic evolution history of the Kuqa Depression. (3) Field investigation and paleostress reconstruction show that the Kuqa Depression has undergone gravity-driven extension in sedimentary cover when the Tianshan uplifted vertically. In hydrocarbon generation study, new developments include (1) setting environmental index to judge high grade source rocks in marine carbonates, and (2) establishing the lower limit of the organic carbon content for effective carbonate source rocks. In petroleum accumulation study, (1) methods of determining paleopressure and paleotemperature of forming fluid inclusions have been established. (2) The petroleum source analysis has indicated that the crude oil in the Lunnan and Tahe oilfields are derived from the source rocks of the Middle and Upper Ordovician. (3) Three generations of oil inclusions from the Lunnan oilfield have been recognized and dated.
- Published
- 2004
14. Provenance and tectonic setting of Late Carboniferous clastic rocks in West Junggar, Xinjiang, China: A case from the Hala-alat Mountains
- Author
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Tao, Huifei, Wang, Qingchen, Yang, Xiaofa, and Jiang, Lin
- Subjects
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CARBONIFEROUS Period , *CLASTIC rocks , *PROVENANCE (Geology) , *PLATE tectonics , *SEDIMENTS , *SEDIMENTARY rocks , *ANALYTICAL geochemistry - Abstract
Abstract: The Late Carboniferous palaeo-tectonic setting of the West Junggar region is comprised of arcs alternating with basins. Geochemical analysis of the sedimentary rocks associated with these arc-related basins was conducted to better constrain the provenance and tectonic setting. Major and trace element geochemistry data of Late Carboniferous mudstones and sandstones in the Hala-alat Mountains suggest that these sedimentary rocks and their source areas are characterized by the following four features: (1) sediments experienced a simple recycling process; (2) a low degree weathering conditions in the source areas; (3) compositional immature of the sedimentary rocks; (4) dominated by intermediate to felsic provenance, with a few intermediate to mafic sediments. Integrated with the palaeo-flow data and previous authors’ works, a fore-arc basin model is proposed for the tectonic setting of the sedimentary rocks. The Sawur arc is the primary provenance and supplies the major intermediate to felsic detrital fragments. The Bozchekul-Chingiz arc and Kexia oceanic island arc are the other two secondary sources. [Copyright &y& Elsevier]
- Published
- 2013
- Full Text
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15. Petrology and geochemistry of chert on the marginal zone of Yangtze Platform, western Hunan, South China, during the Ediacaran-Cambrian transition.
- Author
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WANG, JIANGUO, CHEN, DAIZHAO, WANG, DAN, YAN, DETIAN, ZHOU, XIQIANG, and WANG, QINGCHEN
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CAMBRIAN stratigraphic geology ,PETROLOGY ,GEOCHEMISTRY ,CARBONATES ,CHALCEDONY ,AMORPHOUS substances - Abstract
The Ediacaran-Cambrian transition was one of the most critical intervals in Earth history. During this interval, widespread chert was precipitated, commonly as a stratal wedge in carbonates, along the southern margin of the Yangtze Platform, South China. The chert wedge passes into a full chert succession further basinward to the south-east. Four lithotypes of chert are identified across the marginal zone in western Hunan: mounded, vein, brecciated and bedded chert. The mounded chert is characterized by irregular to digitiform internal fabrics, generally with abundant original vesicles and/or channels that mostly are lined by botryoidal chalcedony cements with minor quartz and barite crystals. The host chert (or matrix) of these mounds is dominated by amorphous cryptocrystalline silica, commonly disseminated with pyrite. The vein chert, with minor quartz locally, generally cross-cuts the overlying dolostone and chert horizons and terminates under the mounded and/or bedded chert bodies. The brecciated chert commonly occurs as splayed 'intrusions' or funnel-shaped wedges and cross-cuts the topmost dolostones. The bedded chert, the most common type, generally is thin to medium-bedded and laminated locally; it is composed of amorphous silica with minor amounts of black lumps. Microthermometry of fluid inclusions from vein and void-lining minerals (mainly quartz and barite) revealed homogenization temperatures from 120 to 180°C for the trapped primary fluids. Compositionally, these chert deposits generally are pure, with SiO
2 > 92 wt%, and only minor Fe2 O3 and Al2 O3 contents, most of which show positive Europium anomalies in rare earth element patterns, especially for the mounded chert. All these data suggest that the marginal zone chert deposits resulted from a low-temperature, silica-rich hydrothermal system, in which the mounded chert was precipitated around the releasing vents, i.e. as silica chimneys. The vein and splayed brecciated chert, however, was formed along the syndepositional fault/fracture conduits that linked downward, while the bedded chert was precipitated in the quieter water column from the fallout of hydrothermal plumes onto the sea floor. These petrological and geochemical data provide compelling evidence and a new clue to the understanding of the extensive silica precipitation; rapid tectono-depositional and oceanic changes during the Ediacaran-Cambrian transition in South China. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
16. Petrography and geochemistry of lower carboniferous greywacke and mudstones in Northeast Junggar, China: Implications for provenance, source weathering, and tectonic setting.
- Author
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Tao, Huifei, Sun, Shu, Wang, Qingchen, Yang, Xiaofa, and Jiang, Lin
- Subjects
- *
PETROLOGY , *GEOCHEMISTRY , *CARBONIFEROUS Period , *GRAYWACKE , *MUDSTONE , *STRUCTURAL geology , *WEATHERING - Abstract
Highlights: [•] Petrography and geochemistry data are applied in this research. [•] The Dulate arc is the primary source area. [•] REE mixing of provenance modelling method is used to determine the source rocks. [•] The sedimentary rocks deposit in a back-arc basin. [•] The back-arc basin formed by the southward subduction of the Zaysan–Erqis Ocean. [Copyright &y& Elsevier]
- Published
- 2014
- Full Text
- View/download PDF
17. Predominance of stratified anoxic Yangtze Sea interrupted by short-term oxygenation during the Ordo-Silurian transition
- Author
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Yan, Detian, Chen, Daizhao, Wang, Qingchen, and Wang, Jianguo
- Subjects
- *
OXYGENATION (Chemistry) , *SILURIAN stratigraphic geology , *GLACIATION , *GLOBAL warming , *GEOCHEMISTRY - Abstract
Abstract: The Ordo-Silurian transition was a critical interval in geological history, during which profound biotic, climatic and oceanic changes occurred. In order to explore the oceanic palaeoredox changes, multiple geochemical proxies, including ratios of S/C, FeHR/FeT, FeP/FeHR and DOP values, are presented here from three sections (Wangjiawan, western Hubei, Sanjiaguan, northern Hunan, and Nanbazi, northern Guizhou) across the Ordo-Silurian boundary on the Yangtze Platform. These palaeoredox data indicate a predominance of stratified, anoxic (ferruginous) ocean on the Yangtze block during this transition, which was interrupted by a brief episode of oceanic oxygenation in the early Hirnantian. This oxygenation, temporally coinciding with the end-Ordovician glaciation and global glacio-eustatic sea level fall, likely resulted from enhanced circulation of polar cold, dense oxygen-rich water onto the low-latitude shelf. The prior and subsequent longer-term episodes of anoxic ocean, particularly the later one which started in the late Hirnantian, occurred in parallel with the rapid climatic warming and sea level rise, which could have slowed down oceanic circulation, thereby enhancing oceanic stratification, anoxia and organic preservation. Oceanic redox changes, together with rapid climatic and sea-level fluctuations, were likely responsible for the stepwise massive demise of the Ordo-Silurian biotic crisis. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
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