Yushu Area Research Articles

Rb‐Sr and Sm‐Nd Isochron Ages of the Dongmozhazhua and Mohailaheng Pb‐Zn Ore Deposits in the Yushu area, southern Qinghai and Their Geological Implications

Abstract:Located on the northeast margin of the Qiangtang terrane between the Jinshajiang suture zone and Bangonghu‐Nujiang suture zone, the Dongmozhazhua and Mohailaheng Pb‐Zn deposits in the Yushu area of Qinghai Province are representative Pb‐Zn deposits of the Pb‐Zn‐Cu polymetallic mineralization belt in the northern part of the Nujiang‐Lancangjiang‐Jinshajiang area, which are in the front belt of the Yushu thrust nappe system. The formed environments of these two deposits are different from those of sediment‐hosted base metal deposits elsewhere in the world. The authors hold that they were formed during the Indian‐Asian continental collision and developed within the fold‐thrust belt combined with thrust and strike‐slip‐related Cenozoic basins in the interior of the collisional zone. Studying on the metallogenic epochs of these two deposits is helpful to the understanding of ore‐forming regularity of the regional Pb‐Zn‐Cu mineralization belt and also to the search for new deposits in this region. The age of the Dongmozhazhua deposit has been determined by the Rb‐Sr isochron method for sphalerite residues, whereas the age of the Mohailaheng deposit has been determined by the Rb‐Sr isochron method for sphalerite residues and the Sm‐Nd isochron method for fluorite. The age of the Dongmozhazhua deposit is 35.0±0.0 Ma ((87Sr/86Sr)0=0.708807) for sphalerite residues. The age of the Mohailaheng deposit is 32.2±0.4 Ma ((87Sr/86Sr)0=0.708514) for sphalerite residues and 31.8±0.3 Ma ((143Nd/144Nd)0=0.512362) for fluorite with an average of 32.0 Ma. Together with the regional geological setting during mineralization, a possible tectonic model for metallogeny of the Dongmozhazhua and Mohailaheng Pb‐Zn deposits has been established. These two ages are close to the ages of the Pb‐Zn deposits in the Lanping and Tuotuohe basins, indicating that it is possible that the narrow 1000‐kilometer‐long belt controlled by a thrust nappe system on the eastern and northern margins of the Tibetan plateau could be a giant Pb‐Zn mineralized belt.

Genome-wide association study of high-altitude pulmonary edema in Han Chinese

High-altitude pulmonary edema (HAPE) is a non-cardiogenic pulmonary edema that is always found among unacclimatized persons after rapid ascent to high altitude, and HAPE is caused by the interaction of genetic and environmental factors. To screen and analyze the susceptibility genes and single nucleotide polymorphisms (SNPs) of HAPE in Han Chinese, the DNA samples of 40 patients with HAPE and 33 healthy controls, who performed the reconstruction tasks from the plain region in Yushu area of Qinghai province during May of 2010 to July of 2012, were scanned by Affymetrix SNP Array 6.0 Chips in this study. Genome-wide association study (GWAS, by PLINK software) was used to screen the susceptibility genes and genetic markers, and a total of 57 SNPs were found to be significantly different between case and control groups (adjust P < 0.05). GO and Pathway enrichment analysis of 74 genes around the 57 SNPs indicated that these genes were significantly correlated with prostanoid metabolic process, arachidonic acid metabolism and nitrogen metabolism (adjust P < 0.05), which were involved in the physiopathologic mechanism of HAPE. Our studies suggest that these genetic polymorphisms and genes were associated with HAPE.

Coseismic Deformation of the 2010 Mw 6.9 Yushu Earthquake Derived from GPS Data

On 13 April 2010 UTC 23:49:17 (Local time 7:49:17 on 14 April 2010), a large earthquake ( M w 6.9) struck Yushu county, Qinghai, China, killing 2,700 people, and causing widespread damage in the high mountainous regions of the central Tibetan Plateau. This event occurred on the pre‐existing left‐lateral strike‐slip Ganzi–Yushu fault, which is the western part of the Yushu‐Ganzi‐Xianshuihe fault zone. The Ganzi‐Yushu fault extends for ∼200 km along a northwest–southeast strike (Wang et al. , 2008). The event of 13 April 2010 is the largest one in this region since the last destructive earthquake about 272 years ago (Zhou et al. , 1996; 1997). Previous studies from geodetic surveys inferred an average slip of 14.4 mm/yr along the Ganzi‐Yushu‐Xianshuihe fault (Gan et al. , 2007). The principal horizontal strain rates over the Yushu area are characterized by a combination of north‐northeast–south‐southwest compression and west‐northwest–east‐southeast extension (Calais et al. , 2006), which are significant at the 95% confidence level. Field investigation revealed an ∼51‐km left‐lateral strike‐slip surface rupture (Chen et al. , 2010; J. Zhang et al. , 2010) with a coseismic displacement of 0.3–3.2 m (Lin et al. , 2011). Satellite image analyses show various lengths of surface breakage ranging between 39 and 80 km (Li et al. , 2011; Tobita et al. , 2011; Zha et al. , 2011). However, estimates from initial seismological inversion show the rupture belt is composed of at least 3 segments, with a total length of 50–70 km. Field observation demonstrates that coseismic surface rupture zone produced by the main shock is 31–33 km in length. Teleseismic waveform analysis suggested that the earthquake could be resolved into two subevents of up to 2.0‐m slip on a 119°‐striking fault dipping southwest (Y. Zhang …

The calculation of Quaternary deposits diffusion coefficient by fault scarps for estimation of earthquake hazards in central Iran

The Yushu segment of the Ganzi–Yushu fault system (central Tibet plateau) is mainly composed by the Yushu fault and the Batang fault. The 2010 Ms 7.1 Yushu earthquake occurred on the Yushu fault, causing huge loss of lives and widespread damages to the densely populated Yushu area. So far, much effort has been devoted to the surface rupture and paleoseismology of the Yushu fault, while the late Quaternary activity of the Batang fault has not received much attention. The Batang fault has a clear geomorphic expression with fault scarps, sag ponds, push-ups, systematic offset of fluvial terraces, and alluvial fans along its trace. Integrated methods of geomorphological mapping, outcrop analysis, trench excavation and logging, optically stimulated luminescence (OSL), and radiocarbon (14C) dating are employed to study the latest Pleistocene and Holocene paleoseismology of the Batang fault. Several paleoearthquakes are identified from geomorphic and stratigraphic evidence between 22 ka and after 2.7 ka. The oldest event (E1) occurred after 22 ka BP, E2 prior to 14 ka BP, E3 within 14 and 9.5 ka BP, E4 within 8.0–7.8 ka BP, E5 prior to 6.7 ka BP, the penultimate event (E6) occurred within 4.3–4.0 ka BP, and the most recent event (E7) occurred after 2.7 ka BP. The average recurrence interval of paleoearthquakes for the Batang fault is about 2000 a in the last ~ 8 ka BP, and the relapse time of the latest paleoearthquake is < 2.7 ka. Co-seismic displacement of the most recent surface-rupturing event is about 3 m, as deduced from the offsets of the youngest terrace risers and of small gullies. Empirical equations between co-seismic displacement and earthquake magnitude reveal that the average magnitude of these events is about 7.3. This study contributes important information for the seismic hazard assessment of the densely populated Yushu area.

Orthopaedic injury analysis in the 2010 Yushu, China Earthquake

ObjectiveBy analysing the injuries of the orthopaedic wounded during the 2010 Yushu earthquake, we aim to provide useful medical information for the rational application and allocation of medical resources and better implementation of medical relief in earthquake-stricken areas. Patients and methodsFive hundred and eighty-two orthopaedic patients injured during the earthquake. The clinical data, injury conditions and epidemiological features (including age composition, gender ratio, distribution of injury, etc.) were collected and analysed. ResultsAltogether 582 orthopaedic patients were analysed. The average age for all patients was 38.8±13.08 years (0–86 years). Adults accounted for 81.62%. There was no gender difference. The most common injuries included limb fractures, pelvic/acetabular fractures and spinal fractures. Fractures accompany with nerve injury were relatively low, only 17 patients account for 2.92%. Fractures complicated by crush syndrome were even lower, only 7 patients account for 1.20%. ConclusionThe patients who experienced fractures in the Yushu earthquake were mostly adults. This was correlated with population composition in Yushu area. This time all the orthopaedic injuries were relative mild with less complication as nerve injury or crush syndrome mainly because of the characteristics of the house structure in Yushu area.

Co-seismic strike-slip surface rupture and displacement produced by the 2010 M W 6.9 Yushu earthquake, China, and implications for Tibetan tectonics

The magnitude (M W) 6.9 (M s 7.1) Yushu earthquake occurred on 14 April 2010 in the Yushu area, central Tibetan Plateau, causing widespread damage in high mountain regions. Field investigations reveal that the earthquake produced a 33-km-long surface rupture zone, with dominantly left-lateral strike-slip along the Yushu Fault of the pre-existing strike-slip Ganzi-Yushu Fault Zone. The co-seismic surface ruptures are characterized by discontinuous shear faults, right-stepping en echelon tensional cracks, and left-stepping mole track structures that indicate a left-lateral strike-slip shear sense for the seismic fault. Field measurements indicate co-seismic left-lateral strike-slip displacements of approximately 0.3–3.2 m (typically 1–2 m), accompanied by a minor vertical component of <0.6 m. The present results show that (i) the Yushu earthquake occurred upon the pre-existing active Ganzi-Yushu Fault Zone, which controlled the spatial distribution of co-seismic surface ruptures and displacements; (ii) the left-lateral strike-slip motion indicates that the Ganzi-Yushu Fault Zone partitions deformation into eastward extrusion of and northeastward shortening the central Tibetan Plateau to accommodate the continuing penetration of the Indian plate into the Eurasian plate.

Geochronological and geochemical constraints on Mesozoic suturing in east central Tibet

This paper reports isotopic, major and minor element geochemistry of igneous and metamorphic rocks from the Kokoxili and Yushu regions of central and eastern Tibet. The first region lies along the Kunlun suture, which separates the Bayan Har‐Songpan Ganze (Songpan) terrane from the Tarim and Qaidam blocks. Two Kokoxili granitoids yield U‐Pb zircon dates of 217 ± 10 and 207 ± 3 Ma (Late Triassic), which represent the time of emplacement, and Rb‐Sr isochron dates of 195 ± 3 and 190 ± 3 Ma (Early Jurassic), which are interpreted as cooling ages. The geochemical signatures of these granitoids suggest that they are related to subduction continuing into the Late Triassic. In the Yushu area, three samples help constrain the age of the Jinsha suture, which separates the Songpan terranes from the Qiangtang blocks. A leucocratic granite and an orthogneiss in the suture zone yield U‐Pb zircon dates of 206 ± 7 and 204 ± 1 Ma, respectively, and a paragneiss south of it, a U‐Pb monazite date of 244 ± 4 Ma. The existence of coeval magmatism in both the Jinsha and Kunlun sutures suggests that the two subduction zones were simultaneously active. Combining isotopic dating with structural evidence on subduction polarity and paleomagnetic reconstructions, we propose that the Kunlun and Qinling block boundaries, which were distinct in the Permian, subsequently formed a continuous, Late Triassic, northward subducting plate margin. Our data suggest that the Jinsha suture correlates with the Benzilan and Nan‐Uttaradit sutures, which together belong to a major Late Triassic subduction zone.