close

Вход

Забыли?

вход по аккаунту

?

j.jseaes.2018.08.015

код для вставкиСкачать
Accepted Manuscript
Palaeontology and U–Pb detrital zircon geochronology of Upper Triassic strata
on the northern margin of the Bangong Co–Nujiang Suture Zone, Tibet: constraints on the age of opening of the Meso-Tethys
Ming Wang, Shuai-Ying Peng, Cai Li, Tian-Yu Zhang
PII:
DOI:
Reference:
S1367-9120(18)30356-0
https://doi.org/10.1016/j.jseaes.2018.08.015
JAES 3619
To appear in:
Journal of Asian Earth Sciences
Received Date:
Revised Date:
Accepted Date:
7 June 2017
30 July 2018
18 August 2018
Please cite this article as: Wang, M., Peng, S-Y., Li, C., Zhang, T-Y., Palaeontology and U–Pb detrital zircon
geochronology of Upper Triassic strata on the northern margin of the Bangong Co–Nujiang Suture Zone, Tibet:
constraints on the age of opening of the Meso-Tethys, Journal of Asian Earth Sciences (2018), doi: https://doi.org/
10.1016/j.jseaes.2018.08.015
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Palaeontology and U–Pb detrital zircon geochronology of Upper
Triassic strata on the northern margin of the Bangong
Co–Nujiang Suture Zone, Tibet: constraints on the age of opening
of the Meso-Tethys
Ming Wang, Shuai-Ying Peng*, Cai Li, Tian-Yu Zhang
College of Earth Sciences, Jilin University, Changchun, 130061, P.R. China
*Corresponding author at: College of Earth Sciences, Jilin University, Changchun 130061,
China
E-mail address: psying@jlu.edu.cn
Fax: +86-431-88584422
1
ABSTRACT
We present the results of field mapping, paleontology, and detrital zircon geochronology
of newly found clastic rocks with intercalations of limestone in the Gaerqin area of Tibet
(Gaerqin Formation). The Gaerqin Formation consists of sandstone, siltstone, and shale with
intercalations of bioclastic limestone. Abundant Late Triassic (Norian) fossils are found in the
limestone beds. The fossils include Distichophyllia norica, Retiophyllia litangensis, and
Mesozoic Chaetetida. In addition, 273 detrital zircons were selected for U–Pb dating,
yielding the following age groups: 210–300, 500–600, 800–1100, 1600–1800, and
2400–2600 Ma. More than 80% of the detrital zircons are older than ~550 Ma, and the most
reliable youngest detrital zircon age for the Gaerqin Formation is ~219 Ma. The results
indicate that the Gaerqin Formation formed in a shallow marine to bathyal continental slope
environment, and represents the first reported Upper Triassic (Norian) strata in the Gaerqin
area of Tibet. The findings also suggest that the Bangong Co–Nujiang Tethys Ocean was a
bathyal basin by the Late Triassic.
Keywords: Tibet; Bangong Co–Nujiang suture zone; Gaerqin; Late Triassic; Coral fossils
1. Introduction
The Bangong–Nujiang Suture Zone (BNS) lies between the Lhasa Block and the
Southern Qiangtang Block to the north (Fig. 1a), and provides a natural laboratory for
studying the features of the Meso-Tethys oceans; i.e., the Paleo-Tethys (Devonian–Triassic),
the Meso-Tethys (latest early Permian–Late Cretaceous; also known in Tibet as the
2
Bangong–Nujiang Tethyan Ocean), and the Ceno-Tethys (Late Triassic–Late Cretaceous)
(Metcalfe, 2006, 2013). The oldest reliable age for the Bangong–Nujiang Tethyan Ocean is
Early Jurassic (Qiu et al., 2004; Xia et al., 2008; Qu et al., 2010), but the timing of the
opening of the Bangong–Nujiang Tethyan Ocean remains debated. Although most scholars
have proposed that this ocean opened in the Late Triassic (Chang and Cheng, 1973; Pan,
1983; Allègre et al., 1984; Pan et al., 1997; Yin and Harrison, 2000; Kapp et al., 2003;
Qiangba et al., 2009), others have proposed that it opened in the Early Jurassic (Qiu et al.,
2004; Xia et al., 2008; Qu et al., 2010) or Middle–Late Jurassic (Wang et al., 1987; Zhang,
2007).
The Gaerqin area is located on the northern margin of the BNS, northern Tibet, and is a
key area for understanding the tectonic evolution of the Tethyan oceans. Since the discovery
of the Duobuzha copper–gold mine, the Gaerqin area has received international attention (Li
et al., 2008, 2011, 2012, 2013, 2014; Xin et al., 2009; Li et al., 2011a; Wu et al., 2012; Dai et
al., 2012; Zhu et al., 2011, 2015; Tang et al., 2014; Li et al., 2017). However, the geological
setting of this area remains enigmatic. Mesozoic deposits are widely distributed in this area
and comprise the Quse and Sewa formations. Further data are required to constrain the age
and depositional environment of the Mesozoic stratigraphy in the Gaerqin area, and two
contrasting views have been proposed: (1) deposition occurred during the Early–Middle
Jurassic in a marine continental slope environment (Chen et al., 2012); and (2) the
stratigraphy is Late Triassic in age and represents an accretionary complex (Li et al., 2011b;
Duan et al., 2013). Further study of the stratigraphy, geochronology, and tectonics of the
Mesozoic stratigraphy in the Gaerqin area is required to reconstruct the geological setting and
3
tectonic evolution of the Bangong–Nujiang Tethyan Ocean.
In this paper, we report fossils discovered in Mesozoic sediments in the Gaerqin area
(herein referred to as the Gaerqin Formation), the results of field mapping, and detrital zircon
ages. The fossils indicate that the Gaerqin Formation is Late Triassic in age and therefore
records the Late Triassic evolution of the Bangong Co–Nujiang Tethys Ocean. We argue that
the Gaerqin Formation was formed during the Norian. Furthermore, we suggest that the
Bangong Co–Nujiang Tethys Ocean was a bathyal basin by the Late Triassic.
2. Geological setting
The Qinghai–Tibetan plateau is located in the eastern section of the Alpine–Himalayan
tectonic domain and has a complex geological history that includes the formation and
evolution of the Paleo-, Meso-, and Ceno-Tethys oceans (Pan et al., 1997; Yin and Harrison,
2000; Torsvik and Cocks, 2013; Zhu et al., 2013; Wang et al., 2014; Wang et al., 2015). The
Qiangtang terrane is bounded by the BNS to the south and the Jinsha suture to the north, the
Karakoram terrane is the westward extension of the Qiangtang Terrane (Fig. 1a; Allègre et al.,
1984; Dewey et al., 1988; Pierce and Mei, 1988; Searle et al., 1991; Burchfiel et al., 1995;
Hsu et al., 1995; Fu et al., 2010; Xu, 2015; Fan et al., 2017). The Qiangtang Block is
subdivided into the southern and northern Qiangtang blocks by the Longmu Co–Shuanghu
Suture Zone (Li et al., 2008; Metcalfe, 2013; Zhai et al., 2013; Zhang et al., 2014). The BNS
traverses the central Tibetan Plateau in an east–west direction (Fig. 1a), extending ~2400 km
from Kashmir in the west, through the Bangong Co, Rutog, Gerze, Dongqiao, Dingqing, and
Jiayuqiao areas, and into Burma, Thailand, and Malaysia in the east. In China, the BNS is
4
subdivided into three segments termed, from west to east, the Bangong–Gerze,
Gerze–Dingqing, and Dingqing–Nujiang segments (Pan et al., 1997; Qiu et al., 2004). The
Gaerqin area is the focus of this study, and is located on the northern margin of the Bangong
Co–Nujiang Suture Zone in the Duolong ore area (~100 km northwest of Gerze County) in
the western segment of the BNS (Fig. 1b).
The study area is geologically complex, with well-developed faulting, widespread
igneous rocks, and abundant copper and gold resources. The regional strata consist mainly of
the Early–Middle Jurassic Quse and Sewa formations and the Early Cretaceous Meiriqiecuo
Formation. The oldest strata in the study area are the early Permian Qudi Formation,
characterized by glaciomarine deposits of the northern margin of Gondwana (Li and Zheng,
1993; Jin, 2002; Carlos et al., 2014; Fan et al., 2015; Wang et al., 2014, 2016). The
Early–Middle Jurassic Quse and Sewa formations are the ore host rock of the Duolong ore
concentrating area. As there is currently no conclusive evidence, previous research has
identified the Quse and Sewa formations based on stratigraphic correlation and sedimentary
features (Chen et al., 2012), and this sedimentary succession is the main focus of this paper.
3. Stratigraphic section and geological features of the Gaerqin Formation
The Gaerqin Formation crops out over an area >50 km2, and the extent of the distribution
is unclear. The Gaerqin Formation is characterized by clastic rocks and comprises thin gray
layers of fine sandstone and siltstone, yellow sandstone, thick coarse sandstone, and
conglomerate. Recently, we found intercalations of bioclastic limestone in the strata for the
first time. Geological field observations show that, from north to south, the sedimentary
5
succession changes from bioclastic limestone, thick coarse sandstone, and conglomerate to
fine sandstone, mudstone, and shale.
The stratigraphic section of the Gaerqin Formation (Fig. 2) shows that there
are at least four depositional cycles in this area. The lower part of each of the depositional
cycles consists predominantly of bioclastic limestone, limestone, and conglomerate, and the
upper part consists of thick coarse sandstone and fine sandstone. Abundant fossils were
identified in some limestone beds (Fig. 2). The fossils include Distichophyllia norica (Fig.
3a–f), Retiophyllia litangensis (Fig. 3g–i), Mesozoic Chaetetida, Mesozoic Spongiomorpha,
Mesozoic Hydrozoa, and Mesozoic Sponges, which belong to the Late Triassic Norian Stage.
These fossils were identified by Liao Weihua from the Nanjing Institute of Geology and
Paleontology, Chinese Academy of Sciences, China.
4. LA–ICP–MS U–Pb dating of zircons from the Gaerqin Formation
4.1 Analytical methods
Zircon grains were separated from rock samples by standard gravimetric and magnetic
methods at the Geological Laboratory at Langfang, Hebei, China. Sample targets of 25 mm
diameter were prepared at the Institute of Geology, Chinese Academy of Geological Sciences,
Beijing, China. Cathodoluminescence (CL) images were taken at the Institute of Physics,
Peking University, Beijing, to inspect individual zircons and select sites for isotope analysis.
The analytical methods are described in Chen et al. (2005). Zircon U–Th–Pb analyses were
performed at the Geological Laboratory Centre, China University of Geosciences, Beijing,
China. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), a New
6
Wave UP 193 nm laser ablation system, and an Agilent 7500a plasma mass spectrometer
were used in this study. The analyses involved the ablation of zircon with an excimer laser
operating at a wavelength of 193 nm and a frequency of 10 Hz. Helium was used as the
carrier gas at a gas flow of 0.8 L/min. The Agilent 7500a ICP–MS instrument operated at
1350 W using a spot diameter of 36 μm. Argon was used as the make-up gas and was mixed
with the carrier gas via a T-connector before entering the ICP at a gas flow rate of 1.13 L/min.
International reference material NIST 612 was used as the external standard and
29
Si as the
internal standard. Isotopic ratio correction for the zircon U–Pb dating was performed using
GLITTER 4.4 and the 91500 zircon international standard (Wiedenbeck et al., 1995). The
final zircon U–Pb age and concordia diagrams were plotted using ISOPLOT 3.0 (Ludwig et
al., 2003). The errors of the individual analyses are quoted at 1σ, whereas the errors for the
weighted mean ages are quoted at 2σ (95% confidence level).
4.2 Analytical results
Three typical samples of sandstone from the area shown in Fig. 1b were selected for
zircon dating. A total of 273 analyses of detrital zircons were undertaken. The U–Pb isotope
dating results are presented in the online Supplementary documents. Representative CL
images of the detrital zircons in the sandstone samples are presented in Fig. 4a. All analyses
are shown on concordia plots (Fig. 4b–d). Ages of <1000 Ma are based on the
ratio, whereas older ages are based on the
206
206
Pb/238U
Pb/207Pb ratio. Most of the zircons are
oval-shaped with length-to-width ratios of 2:1 to 3:2, and have grain sizes of 100–250 μm.
Most of the zircons show oscillatory zoning and Th/U ratios of 0.01–2.35 (average of 0.60),
7
consistent with a magmatic origin (Belousova et al., 2002; Corfu et al., 2003; Hoskin and
Schaltegger, 2003). A small number of zircons have long columnar shapes. Some grains
display metamorphic structures and have low Th/U ratios, indicating these zircons were
derived from metamorphic rocks. The age spectra can be classified into five groups: 210–300,
500–600, 800–1100, 1600–1800, and 2400–2600 Ma. The youngest detrital zircon age is
~219 Ma.
Ninety-nine zircon grains from sample D14T27 were selected for zircon dating. Most of
the data plot on or near the concordia line and yield ages of 0.2–2.6 Ga (Fig. 4b). The oldest
zircon has an age of 2591 Ma. Eleven grains yield ages of 200–300 Ma, 9 grains yield ages of
550–650 Ma, 11 grains yield ages of 900–1100 Ma, 22 grains yield ages of 1600–1800 Ma,
and 7 grains yield ages of 2400–2500 Ma. The youngest detrital zircon age is ca. 249 Ma.
Ninety-nine zircon grains from sample D14T31 were selected for zircon dating. Most of
the data plot on or near the concordia line and yield ages of 0.2–2.7 Ga (Fig. 4c). The oldest
zircon has an age of 2699 Ma, and 10 grains yield ages of 250–300 Ma, 9 grains yield ages of
550–650 Ma, 9 grains yield ages of 800–1100 Ma, 30 grains yield ages of 1600–1900 Ma,
and 4 grains yield ages of 2400–2500 Ma. The youngest detrital zircon age is ca. 249 Ma.
Seventy-five zircon grains from sample DT16 were selected for zircon U–Pb dating.
Most of the data plot on, or near, the concordia line, and yield ages of 220–2500 Ma (Fig. 4d).
The oldest zircon has an age of 2847 Ma. Eight grains yield ages of 250–300 Ma, 1 grain
yields ages of 550–650 Ma, 2 grains yield ages of 800–1100 Ma, 25 grains yield ages of
1600–1900 Ma, and 5 grains yield ages of 2400–2500 Ma. The youngest detrital zircon age is
ca. 226 Ma.
8
5. Discussion
5.1 Late Triassic sedimentary record of the Meso-Tethys
The Gaerqin Formation is located on the northern margin of the Bangong Co–Nujiang
Suture Zone. In previous studies, these strata were identified as belonging to the Quse
Formation (Chen et al., 2012), but there is no conclusive evidence of such a correlation. The
Quse Formation in the Sewa area was originally described as comprising dark-gray mudstone,
shale, and limestone. The fossils in the Quse Formation include Early Jurassic ammonoids
and brachiopods (Wen, 1979; Yin et al., 2003; Wang, 2008a, b); these fossils have not been
found in the Gaerqin Formation.
Zircon dating as part of this study shows that the youngest detrital zircon age of the
Gaerqin Formation is ca. 219 Ma, consistent with the fossil ages. The coral fossils from the
Gaerqin Formation include Distichophyllia norica and Retiophyllia litangensis, first
identified by Liao Weihua of the Nanjing Institute of Geology and Paleontology, Chinese
Academy of Sciences, China. There are many reports of such coral fossils in northern Tibet,
which are representative of the Late Triassic Norian Stage (Mǜnster et al., 1841; Cuif, 1974;
Liao et al., 1994; Li et al., 2007; Ji et al., 2010; Bo et al., 2014). Triassic coral fossils of the
Qinghai–Tibet Plateau are distributed mainly in the Himalayan, Lhasa, and Qiangtang
terranes, and Songpan–Ganzi Fold Belt (from south to north; Bo et al., 2017a, b). A
double-layer structure comprising a basaltic basement with an oceanic sedimentary cover
sequence (resembling an ocean island) has been described in the study area (Gufeng ocean
island; Fig 1b; Fan et al., 2017). Conodont fossils of Epigondolella abneptis subspecies A
9
were identified within the Gufeng ocean island limestone (Fig. 4), which is typical of the Late
Triassic Norain Stage (Michael, 1983; Fan et al., 2017). The Gufeng ocean island is located
~5 km from the Gaerqin area (Fig. 1b) and may be part of the Gaerqin Formation. These
results imply that the Gaerqin Formation formed during the Late Triassic Norian Stage and
represents a Late Triassic sedimentary record of the Tethys Ocean.
5.2 Paleogeographic reconstructions
Geological field observations show that the sedimentary succession of the Gaerqin
Formation changes from north to south, from a sequence dominated by bioclastic limestone,
thick coarse-grained sandstone, and conglomerate, to one dominated by fine-grained
sandstone, mudstone, and shale. In the north, the sediments contain parallel bedding, cross
bedding, and rhythmical bedding. In the south, the bedding structures include horizontal
bedding, graded bedding, parallel bedding, and cross bedding. Wavy bedding is well
developed, and hummocky ripple marks at the base of sandstone beds have been identified.
The Gaerqin Formation was formed from clastic sediments deposited by turbidity currents in
a bathyal sea (Fig. 5). Thus, from north to south, the sedimentary environment changes from
a shallow marine continental shelf to a bathyal setting.
5.3 Regional stratigraphic correlation
The Triassic was a key stage in the evolution of the Tethyan oceans, and the opening of
the Meso-Tethys may have occurred during this time (Zhu, 1984; Metcalfe, 2013). It has
10
been suggested that the Bangong Co–Nujiang suture zone was the main suture zone of the
Meso-Tethys. However, the timing of opening of the Bangong Co–Nujiang Tethys Ocean
remains enigmatic, and various timings have been proposed: (1) Carboniferous–Early
Triassic (Yin et al., 1998); (2) late Permian–Early Triassic (Ren et al., 2004; Huang et al.,
2012); (3) Late Triassic (Chang and Cheng, 1973; Pan, 1983; Allègre et al., 1984; Pan et al.,
1997; Yin and Harrison, 2000; Wang et al., 2002; Kapp et al., 2003; Qiangba et al., 2009);
and (4) Early Jurassic (Qiu et al., 2004; Wang et al., 2008; Xia et al., 2008; Qu et al., 2010).
The Gaerqin Formation is located on the northern margin of the Bangong Co–Nujiang
suture zone, which suggests that before the Late Triassic the Bangong Co–Nujiang Tethys
Ocean was already a bathyal basin. According to the regional stratigraphic correlation, there
are at least three sedimentary successions that have similar characteristics to the Gaerqin
Formation. They are the Lower Jurassic Quse Formation, the Upper Triassic Riganpeicuo
Formation, and the Upper Triassic Quehala Formation. The Quse Formation is distributed
mainly at the northern margin of the Bangong Co–Nujiang suture zone, similar to the Gaerqin
Formation. However, the fossils of the Quse Formation mainly comprise ammonoids and
brachiopods (Wen, 1979; Wang, 2008a, b), which are generally considered to be Early
Jurassic in age (Wen, 1979; Yin et al., 2003; Wang, 2008a, b).
The Upper Triassic Riganpeicuo Formation is composed mainly of limestone and
bioclastic limestone, deposited as part of a stable carbonate platform. The fossils of the
Riganpeicuo Formation include bivalves, corals, and snails (Wang et al., 2002; Li et al., 2007;
Zhu et al., 2010; Ma et al., 2011; Hou et al., 2014). Overall, the characteristics of the
Riganpeicuo Formation are different from those of the Gaerqin Formation. The Upper
11
Triassic Quehala Formation is distributed mainly on the southern margin of the Bangong
Co–Nujiang suture zone, and there are no reports of this formation in the study area. The
lithology of the Quehala Formation comprises pink sandstone, fine sandstone, sandstone, and
limestone deposited in a marine bathyal sedimentary environment (Wang et al., 2002; Liu et
al., 2003; Chen et al., 2005). The sedimentary environment of the Quehala Formation is
similar to that of the Gaerqin Formation, although the areal distributions differ.
Synthesizing the above analysis, we tentatively suggest that the Gaerqin Formation
formed in the Late Triassic Norian Stage, in a shallow marine to bathyal continental slope
environment. The regional stratigraphic correlation suggests that the Gaerqin Formation is
similar to the Quehala Formation in lithology and sedimentary environment, but has a
different areal distribution. Nevertheless, the Gaerqin Formation represents the first strata of
the Late Triassic Norian Stage to be recognized in the Duolong ore concentrating area. This
research indicates that the ore host rock of the Duolong ore concentrating area formed, at
least partially, during the Late Triassic, and also indicates that by the Late Triassic, the
Bangong Co–Nujiang Tethys Ocean was already a bathyal basin.
6. Conclusions
(1) The newly recognized strata of the Gaerqin Formation, located on the northern margin of
the Bangong Co–Nujiang Suture Zone, were deposited during the Norian Stage of the
Late Triassic and represent a Late Triassic sedimentary record of the Meso-Tethys Ocean.
(2) The main lithologies of the Gaerqin Formation are bioclastic limestone, thick
coarse-grained sandstone, conglomerate, fine-grained sandstone, and shale. Coral fossils
12
include Distichophyllia norica and Retiophyllia litangensis, which are representative of
the Late Triassic Norian Stage.
(3) The Gaerqin Formation was formed by turbidity currents in a shallow marine to bathyal
continental slope environment. From north to south, the sedimentary environment
changes from a shallow marine continental shelf to a bathyal setting.
(4) The detrital zircon ages of the Gaerqin Formation clastic rocks fall into five groups:
210–300, 500–600, 800–1100, 1600–1800, and 2400–2600 Ma. The most reliable
youngest detrital zircon age is ~219 Ma.
(5) The Bangong Co–Nujiang Tethys Ocean was a bathyal basin prior to the Late Triassic.
Acknowledgments
We thank the journal editor for useful comments and careful handling of the manuscript.
We are grateful to Ian Metcalfe and an anonymous reviewer for constructive comments that
improved the quality of this paper. We thank the staff of the Geological Laboratory Centre of
China, University of Geosciences (Beijing), for help with the LA–ICP–MS zircon U–Pb
dating, and the staff of the Institute of Physics, Peking University, for help with the CL image
analysis. We also thank Tang Juxing, Song Yang, Xie Chaoming, and Fan Jianjun for help in
the field, and Liao Weihua for help with the identification of fossils. This research was
funded by the National Science Foundation of China (Grant no. 41602230), the China
Postdoctoral Science Foundation (Grant no. 2016T90248), and the China Geological Survey
(Grant nos. DD20160026 and 121201010000150014).
13
References
Chang, C.F., Cheng, H.L., 1973. Some tectonic features of the Mt. Jolmo Lungma area, southern Tibet,
China. Scientia Sinica 16, 257.
14
Chen, Y.L., Xu, T.D., Zhang, K.Z., Gou., Y.D., and Wen, J.H., 2012. geologic maps of Wuma, Tibet:
China geological survey, scale 1∶ 250 000, 1 sheet.
Cuif, J.P., 1974. Recherches surles Madreporaires du Trias. II. Astraeoida. Revision desgenres
Montlivaltia et Thecosmilia. Etude de quelques types structuraux du Trias de Turquie. Bull. Mus.
Nat. Hist. Nat. Paris 3, 290–400.
Dai, J.J., Qu, X.M., 2012. Structural Pattern and Alteration Information Derived from Remote Sensing
Data and Their Significance for Ore Search in the Duolong Copper-Ore Concentration Area of Tibet.
Geology and Exploration 48, 815–822(in Chinese with English abstract).
Deng
15
Duan, Z.M., Li, G.M., Zhang, H., Duan, Y.Y., 2013. The formation and its geologic significance of Late
Triassic–Jurassic accretionary complexes and constraints on metallogenic and geological settings in
Duolong porphyry copper gold ore concentration area, northern Bangong Co–Nujiang suture zone,
Tibet. Geological Bulletin of China 32, 742–750 (in Chinese with English abstract).
:
16
Huang, Q.S., Shi, R.D., Ding, B.H., Liu, D.L., Zhang, X.R., Pan, S.Q., Zhi, C.X., 2012. Re-Os isotopic
evidence of MOR-type ophiolite from the Bangong Co for the opening of Bangong-Nujiang Tethys
Ocean. Acta Petrologica et Mineralogica 31, 465–478(in Chinese with English abstract).
in Chinese with English abstract
Li, C., Dong, Y.S., Zhai, Q.G., Wang, L.Q., Yan, Q.R., Wu, Y.W., He, T.T., 2008. Discovery of
Eopaleozoic ophiolite in the Qiangtang of Tibet Plateau: evidence from SHRIMP U–Pb dating and its
tectonic implications. Acta Petrol. Sin 24, 31–36 (in Chinese with English abstract).
Li, G.M., Li, J.X., Qin, K.Z., Duo, J., Zhang, T.P., Xiao, B., Zhao, J.X., 2011a. Geology and Hydrothermal
Altermation of the Duobuza Gold-Rich Porphyry Copper Dsitrict in the Bangongco Metallogenetic
Belt, Northwest Tibet. Resourse Geology 62, 99–188.
Li, G.M., Duan, Z.M., Liu, B., Zhang, H., Dong, S.L., Zhang, L. 2011b. The discovery of Jurassic
accretionary complexes in Duolong area, northern Bangong Co-Nujiang suture zone, Tibet,and its
geologic significance. Geological Bulletin of China 30, 1256–1260(in Chinese with English
17
abstract).
Li, J.X., Li, G.M., Qin, K.Z., Xiao, B., 2008. Geochemistry of porphyries and volcanic rocks and
ore-forming geochronology of Duobuza gold-rich porphyry copper deposit in Bangonghu belt, Tibet:
constraints onmetallogenic tectonic settings. Acta Petrologica Sinica 24, 531–543 (in Chinese with
English abstract).
Li, J.X., Qin, K.Z., Li, G.M., Xiao, B., Zhao, J.X., Chen, L., 2011. Magmatic-hydrothermal evolution of
the Cretaceous Duolong gold-rich porphyry copper deposit in the Bangongco metallogenic belt, Tibet:
evidence from U–Pb and 40Ar/39Ar geochronology. Journal of Asian Earth Sciences 41, 525–536.
Li, J.X., Li, G.M., Qin, K.Z., Xiao, B., Chen, L., Zhao, J.X., 2012. Mineralogy andmineral chemistry of
the Cretaceous Duolong gold-rich porphyry copper deposit in the Bangongco arc, northern Tibet.
Resource Geology 62, 19–41.
Li, J.X., Qin, K.Z., Li, G.M., Xiao, B., Zhao, J.X., Cao, M.J., Chen, L., 2013. Petrogenesis of ore-bearing
porphyries from the Duolong porphyry Cu–Au deposit, central Tibet: evidence from U–Pb
geochronology, petrochemistry and Sr–Nd–Hf–O isotope characteristics. Lithos 161, 216–227.
Li, X.K., Li, C., Sun, Z.M., Wang, M., 2017. Origin and tectonic setting of the giant Duolong Cu–Au
deposit, South Qiangtang Terrane, Tibet: Evidence from geochronology and geochemistry of Early
18
Cretaceous intrusive rocks. Ore Geology Reviews 80, 61–78.
Metcalfe, I., 2006. Paleozoic and Mesozoic tectonic evolution and palaeogeography of East Asian crustal
fragments: the Korean Peninsula in context. Gondwana Research 9, 24 46.
Michael, J.O., 1983. Epigondolella populations and their phylogeny and zonation in the Upper Triassic.
19
Fossil and Strata 11, 177–192.
Mǜnster., Zu, G.G., 1841. Beitrage zur Geogosis and Petrefactenkundedes sǜdostlichen Tirols . I. Planzen
thiere, 25–39.
Pan, G.T., 1983. An evolution of Tethys in global ocean–continent transGroup. Tethyan Geology 18,
23–40 (in Chinese with English abstract).
Qiangba, Z.X., Xie, Y.W., Wu, Y.W., Xie, C.M., Li, Q.L., Qiu, J.Q., 2009. Zircon SIMS U–Pb dating and
its significance of cumulate gabbro from Dengqen ophiolite, eastern Tibet, China. Geological
Bulletin of China 28, 1253–1258 (in Chinese with English abstract).
Qiu, R.Z., Zhou, S., Deng, J.F., Li, J.F., Xiao, Q.H., Cai, Z.Y., 2004. Dating of gabbro in the Shemalagou
ophiolite in the western segment of the Bangong Co–Nujiang ophiolite belt, Tibet–With a
discussion of the age of the Bangong Co–Nujiang ophiolite belt. Geological China 31, 262–268
(in Chinese with English abstract).
20
∶
She, H.Q., Li, J.W. Ma, D.F., Li, G.M., Zhang, D.Q., Feng, C.Y., Qu,W.J., Pan, G.T., 2009. Molybdenite
Re–Os and SHRIMP zircon U–Pb dating of Duobuza porphyry copper deposit in Tibet and its
geological implications. Mineral Deposits 28, 737–746 (in Chinese with English abstract).
Tang, J.X., Sun, X.G., Ding, S., Wang, Q., Wang, Y.Y., Yang, C., Chen, H.Q., Li, Y.B., Li, Y.B., Wei, L.J.,
Zhang, Z., Song, J.L., Yang, H.H., Duan, J.L., Gao, K., Fang, X., Tan, J.Y., 2014. Discovery of the
Epithermal Deposit of Cu (Au-Ag) in the Duolong Ore Concentrating Area, Tibet. Acta Geoscientica
Sinica 35, 6 10
.
Wang, M., Li, C., Wu, Y.W., Xie, C.M., 2014. Cause of the basic–ultrabasic rocks in southern Qiangtang,
northern Tibet. International Geology Review 56, 187–205.
Wang, M., Li, C., Xie, C.M., Xu, J.X., Li, X.K., 2015. U–Pb zircon age, geochemical and Lu–Hf isotopic
21
constraints of the Southern Gangma Co Basalts in the Central Qiangtang, northern Tibet.
Tectonophysics 657, 219–229.
Wang, M., Li, C., Xie, C.M., 2016. Dating of detrital zircons from the Dabure clastic rocks: the discovery
of Neoproterozoic strata in central Qiangtang, Tibet. International Geology Review 58, 216–227.
Wang, Y.S., Zheng, C.Z., 2008a. Gypsum beds of the Elrly Kurassic Quse formation in the Biloucuo area
of the Southern Qiangtang basin, Northern Tibet. Journal of stratigraphy 32, 321–326 (in Chinese
with English abstract).
Wang, Y.S., Zhang, S.Q., Zheng, C.Z., Li, Q.W., Feng, D.C., Li, X.B., Yu, X.W., 2008b. Biostratlgraphic
of the Middle Jurassic Sewa,Shaqiaomu and Bi Qu formations in the Quruiqianai area,south
Qiangtang basin,northern Tibet,China. Geological Bullean of China 27, 92–100 (in Chinese with
English abstract).
Wen, S.X., 1979. New information about the strata in north Tibet. Journal of stratigraphy 3, 150–156
.
Wiedenbeck, M., Alle, P., Corfu, F., 1995. Three natural zircon standards for U–Th–Pb, Lu–Hf, trace
element and REE analyses. Geostandards and Geoanalytical Research 19, 1–23.
Wu, D.X., Zhao, Y.Y., Liu, C.Q., Xu, H., Li, Y.C., Li, Y.B., Li, X.G., 2012. Geochemical Indicators of
Porphyry Copper Deposits in the Dobzha Ore Concentration Area, Tibet. Acta Geoscientica Sinica 33,
185–196 (in Chinese with English abstract).
Xia, B., Xu, L.F., Wei Z.Q., Zhang, Y.Q., Wang, R., Li, J.F and Wang, Y.B., 2008. SHRIMP zircon dating
22
of gabbro from the Donqiao Ophiolite in Tibet and its geological implications. Acta Geological
Sinica 82, 528–531 (in Chinese with English abstract).
Xin, H.B., Qu, X.M., Wang, R.J., Liu, H.F., Zhao, Y.Y., Huang,W., 2009. Geochemistry and Pb, Sr, Nd
isotopic features of ore–bearing porphyries in Bangong Lake porphyry copper belt, western Tibet.
Mineral Deposits 28, 785–792 (in Chinese with English abstract).
23
Zhu, X.P., Chen, H.A., Ma, D.F., Huang, H.X., Li, G.M., Li, Y.B., Li, Y.C., 2011. Re–Os dating for the
molybdenite from Bolong porphyry copper–gold deposit in Tibet, China and its geological
significance. Acta Petrol. Sin 27, 2159–2164 (in Chinese with English abstract).
Zhu, X.P., Chen, H.A., Liu, H.F., Ma, D.F., Li, G.M., Zhang, H., Liu, C.Q., Wei, L.J., 2015.
Geochronology and geochemistry of porphyries fromthe Naruo porphyry copper deposit, Tibet and
their metallogenic significance. Acta Geol. Sin 89, 109–128 (in Chinese with English abstract).
Figure Captions
Fig. 1. (a) Tectonic framework of the Tibetan Plateau showing the study area. (b) Geological
map of the Gaerqin area, southern Qiangtang, Tibet. Age data sources from Li et al. (2008,
2011, 2013, 2014), Li et al. (2015), She et al. (2009), Zhu et al. (2011), Lv (2012), Chen et al.
(2013), and Xu et al. (2017).
24
Fig. 2. Stratigraphic section and outcrop photographs of the Gaerqin Formation.
Fig. 3. (a–i) Field photographs and photomicrographs of coral fossils from the Gaerqin
Formation. (j–l) CL images of conodont fossils, after Fan et al. (2017).
Fig. 4. (a) Representative CL images of detrital zircons from sandstone sample D14T27. (b)
U–Pb concordia diagram for zircons from sample D14T27 (99 zircons). (c) U–Pb concordia
diagram for zircons from sample D14T31 (99 zircons). (d) U–Pb concordia diagram for
zircons from sample DT16 (75 zircons).
Fig. 5. Model of the Late Triassic depositional environment of the Gaerqin Formation.
25
Highlights:



The newly recognized strata in the Gaerqin area (Gaerqin Formation) formed in the Norian Stage of
the Late Triassic.
The Gaerqin Formation is the first reported Late Triassic Norian strata in the Duolong ore
concentrating area of Tibet.
The Bangong Co–Nujiang Tethys Ocean was already a bathyal basin before the Late Triassic.
26
Документ
Категория
Без категории
Просмотров
0
Размер файла
1 950 Кб
Теги
015, 2018, jseaes
1/--страниц
Пожаловаться на содержимое документа