Zircon U–Pb Ages of the Mianning–Dechang Syenites, Sichuan

Ore Geology Reviews 64 (2015) 554–568

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Zircon U–Pb ages of the Mianning–Dechang syenites, Sichuan Province, southwestern China: Constraints on the giant REE mineralization belt and its regional geological setting

Yan Liu a,ZengqianHoua,⁎, Shihong Tian b,QichaoZhangc, Zhimin Zhu d,JianhuiLiue a Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China b Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, PR China c Chinese Academy of Geological Sciences, Beijing 100037, PR China d Institute of Multipurpose Utilization of Mineral Resources, Chinese Academy of Geological Sciences, Chengdu 610041. PR China e Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, PR China article info abstract

Article history: The Himalayan Mianning–Dechang (MD) rare earth element (REE) belt in western Sichuan Province, southwest- Received 16 August 2013 ern China, is approximately 270 km long and 15 km wide, and contains total reserves of more than 3 Mt of light Received in revised form 27 March 2014 REEs (LREEs), comprising one giant (Maoniuping), one large (Dalucao), two small–medium-sized (Muluozhai Accepted 28 March 2014 and Lizhuang), and numerous smaller REE deposits. The belt occurs within the eastern Indo-Asian collision Available online 13 April 2014 zone (EIACZ), where its location is controlled by large-scale strike-slip faults and tensional ﬁssure zones. Himalayan carbonatite–syenite complexes consist predominantly of alkaline syenite stocks and carbonatite Keywords: SHRIMP U–Pb dating sills or dikes that host REE mineralization. Previous studies have reported inconsistent ages for alkaline Syenite magmatism syenite formation and REE mineralization. Here, we present new results of sensitive high- Mianning–Dechang REE belt resolution ion micro-probe U–Pb dating of zircons from syenites from the Dalucao, Maoniuping, Lizhuang and Sichuan Province Diaoloushan areas, the ﬁrst systematic and precise age determinations for these rocks in the MD belt. The Southwestern China new data give concordant ages of 12.13 ± 0.19 and 11.32 ± 0.23 Ma for the Dalucao deposit, 22.81 ± 0.31 and 21.3 ± 0.4 Ma for Maoniuping, 26.77 ± 0.32 Ma for Muluozhai, and 27.41 ± 0.35 Ma for Lizhuang. These ages, which should be regarded as maximum ages for the REE mineralization in the study area, can be split into two groups, i.e. 11–12 Ma in the southern part of the MD belt and 12–27 Ma in the northern part, suggesting a progression of magmatism from north to south. These data suggest that the majority of carbonatite–syenite magmatism within the EIACZ occurred during the main stage of Himalayan metallogenesis. The ages presented in this study suggest that strike-slip shear along the MD belt was initiated at ca. 27 Ma and ended ca. 12 Ma. This timing is consistent with movements along the adjacent Ailaoshan–Red River strike-slip fault in southeastern Tibet (to the south of the MD belt) and one of the three Cenozoic strike-slip faults in eastern Tibet. Ascent of an asthenospheric mantle diapir beneath the EIACZ in the Cenozoic may have provided a thermal mechanism for the generation of magmas that formed the carbonatite–syenite complexes in the study area. Alternatitvely, the magmas may have been generated by decompression melting associated with the transition from a transpressional to a transtensional regime at 38–40 Ma. The precise age results for syenite magmatism in the study area indicate that this transition occurred prior to carbonatite–syenite magmatism and the formation of the MD REE belt, which is consistent with the regional tectonic model. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Langshan–Baiyan Obo Rift in northern China (Wang and Li, 1992). Other REE deposits occur in continental collision zones, such as the The majority of rare earth element (REE) deposits associated with Himalayan Mianning–Dechang (MD) REE belt in the western part of carbonatite–syenite complexes occur in continental rift zones, such as Sichuan Province, southwestern China. Such deposits are associated the East African Rift (Mitchell and Garson, 1981) and the Proterozoic with Cenozoic carbonatite–syenite complexes of the eastern Indian– Asian collision zone (EIACZ), a region of high topographic relief that is bounded by Cenozoic strike-slip faults (Fig. 1; Hou and Cook, 2009; Hou ⁎ Corresponding author at: Institute of Geology, Chinese Academy of Geological et al., 2003, 2006a,b; Yin and Harrison, 2000). The MD REE belt, which Sciences, Baiwanzhuang Road 26 #, Xicheng District, 100037 Beijing, PR China. ﬁ Tel.: +86 1068990617. is one of the most economically signi cant mineral belts in China, is E-mail address: [email protected] (Z. Hou). 270 km long and 15 km wide, and hosts one giant (Maoniuping), one

large (Dalucao), and two medium-sized REE deposits (Muluozhai and Lizhuang), in addition to numerous other mineralized carbonatite– syenite complexes (Fig. 2). The REE belt is located within the Panxi Rift, a Permian paleorift zone, which was formed as a result of the Emeishan mantle plume (Cong, 1988; Zhang et al., 1988). Previous dating of both References Tian et al. (2008a,b) Tian et al. (2006) Yuan et al. (1995) Tian et al. (2008b) host rocks and gangue minerals, however, indicates that these REE deposits formed during Himalayan metallogenesis (40–10 Ma; Pu, 2001; Tian et al., 2008a,b; Yuan et al., 1995), suggesting formation during collisional orogenesis rather than continental rifting. This indicates that ed)

ﬁ the timing of mineralization in this area is important for constraining the type of mineralization within this giant REE belt, the processes that formed the carbonatite–syenite complex within the belt, and the geodynamic setting of the study area. Previous studies have used a num- Os – ber of differing analytical techniques, isotope systems and minerals to Inductively coupled plasma mass spectrometry (ICP-MS) (error not speci date these REE deposits, yielding a wide range of ages that are often inconsistent or contradictory, even for dates obtained within the same deposit. Such problems are exempliﬁed by the interpreted formation age of the Lizhuang deposit (30.55 ± 0.5 Ma, Ar–Ar on biotite; 28.5 Ma, model age, Re–Os on molybdenite), which is older than the carbonatite–syenite complex that hosts the deposit (27.1 Ma, total fusion age, Ar–Ar on microcline; Tian et al., 2008b)(Table 1), whereas the local geology suggests that the carbonatite–syenite complex formed before the development of REE mineralization (Hou et al., 2006a; Hou et al., 2009). Furthermore, 27.1 Ma is a total fusion age rather than a plateau age, which cannot represent an accurate age for syenite in

Ar Re the Lizhuang deposit (Tian, 2005). A similar situation exists for the – Flame spectrophotometer + integrated database management system (FP + IDMS) 40.3 ± 0.70 Ma (Bi) 31.7 ± 0.70 Ma (Af) Muluozhai deposit, whose age (35.5 ± 0.5 Ma, Ar–Ar on phlogopite) is older than the age of the carbonatite–syenite complex (31.2 ± 0.56 Ma, Ar–Ar on microcline) that hosts the deposit (Tian et al., 2006). Single deposit can have multiple mineralization ages that differ by up to 10 Ma, a signiﬁcant discrepancy considering that the entire MD REE belt formed during the Himalayan orogenesis. This is exempliﬁed

Ar K by the Maoniuping deposit within the MD REE belt, where bastnäsite– – 35.5 ± 0.5 Ma (Ph) 12.95 ± 0.22 Ma (Mu) Mass spectrometer (MS) 13.33 ± 0.41 Ma (Mu) 30.55 ± 0.5 Ma (Bi)aegirine–augite–ﬂuorite 28.5 Ma (model age) –barite and bastnäsite–barite–calcite veins yielded ages of 40.3 and 31.7 Ma, respectively; a much younger U–Pb age of 12.2 Ma, measured on zircons by isotope-dilution thermal ioniza- Dechang REE metallogenic belt, southwestern Sichuan.

– tion mass spectrometry (ID-TIMS), was regarded to make the onset the of the REE mineralization at the late stage of formation of the – – ed) carbonatite syenite complex. It is unclear at present if an older U Pb ﬁ age of 22.4 Ma, also measured on zircons by ID-TIMS, could represent the timing of formation of the carbonatite–syenite complex at Maoniuping (Yuan et al., 1995)(Table 1). These ages imply that the REE

Pb K mineralization is much older than the formation of the carbonatite– – 12.2 Ma (Sy) 22.4 Ma (Sy) (total fusion age) (error not speci Isotopic dilution thermal ionization mass spectrometry (ID-TIMS) syenite complex. However, the difference between the formation ages

rocline; Mo = molybdenite; Mu = muscovite; Ph = phlogopite; Sy = syenite. of the coarse-grained mineralized veins and their host igneous rocks is still unclear, because the emplacement of syenite and carbonatite in the Maoniuping REE deposit has not been accurately dated yet. In previous studies, most syenite formation ages were measured on muscovite or microcline using Ar–Ar methods. Considering the lower closure temperature of these minerals compared with those of zircon and syenites and the fact that carbonatite and REE deposits are spatially close or adjacent to Pb U – 12.13 ± 0.19 Ma (Sy) (this study) 11.32 ± 0.23 Ma (Sy) (this study) (this study) 21.30 ± 0.4 Ma (Sy) (this study) 27.41 ± 0.35 Ma (Sy) (this study) microprobe (SHRIMP) 12.99 ± 0.94 Ma (Ca) 26.77 ± 0.32 Ma (Sy) (this study) one another, syenites could have been readily affected by ore-forming or other later-stage ﬂuids, meaning that the Ar–Ar dates may not repre- syenite complexes and their mineralization in the Mianning – sent the actual age of syenite crystallization. This is particularly relevant ed)

ﬁ to understanding the MD deposits, because several million years of discrepancy are signiﬁcant, considering that these deposits formed between 27 and 10 Ma. However, these ambiguous ages have been used to infer the formation ages of syenites, carbonatites, ore-forming and gangue Ar U – minerals in the MD REE belt, which has led to problematic interpreta- (total fusion age) (Mc from Sy) (error not speci (Mc from Sy) tions. For example, older, rather than accurate, ages were used to inter- pret Sr, Nd and Pb isotope data and the difference in ages would lead to discrepancies in isotope results and geological interpretations. Even in re- cent studies, both 40.3 Ma and 27.8 Ma were considered as the formation age of syenite at the Maoniuping deposit (Hou et al., 2006a; Hou et al., 2009; Xie et al., 2009; Xu et al., 2008; Xu et al., 2012). Importantly, no re- Maoniuping 22.81 ± 0.31 Ma (Sy) Analytical techniques Mass spectrometer (MS) Sensitive high-resolution ion DalucaoLizhuang 14.53 ± 0.31 Ma (Sy) 27.1 Ma Deposits Geochronology of syenites or carbonatites Mineralization age Isotope system K Muluozhai 31.2 ± 0.56 Ma Table 1 Summary of the geochronology of carbonatite Abbreviations: Af = arfvedsonite; Bi = biotite; Ca = carbonatite; Mc = mic liable ages have been obtained for these rocks to date. Age determinations 556 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568

Fig. 1. Simpliﬁed tectonic map of the Himalayan–Tibetan orogen. Modiﬁed after Yin and Harrison (2000) and Hou et al. (2003).

using sensitive high-resolution ion microprobe (SHRIMP) dating of zircon 2. Geological and tectonic setting of the study area are necessary if the ages of formation of the MD carbonatites and their associated deposits are to be accurately and precisely determined. At The following description of the geological and tectonic setting of present, the timing of formation of syenites along the MD belt is unclear, the Himalayan MD REE belt is taken largely from Hou et al. (2009). which limits our understanding of its evolution, tectonic controls on REE The belt is located on the western margin of the Yangtze Craton metallogeny, and of the geodynamic setting of the study area. (Fig. 1) within the Cenozoic EIACZ. Previous research implies that the In eastern Tibet, late-collisional metallogenesis (~40–26 Ma) timing of REE mineralization associated with Cenozoic carbonatite– was developed within a transform structure that was dominated by syenite complexes delineates the 10–40 Ma Himalayan metallogenic Cenozoic strike-slip faulting, shearing and thrusting, and produced epoch (Table 1)(Hou et al., 2006b). The basement of the Yangtze one of the most economically significant metallogenic provinces in Craton consists of Archean high-grade metamorphic rocks, Proterozoic China (Fig. 1). The formation of REE mineralization associated metasedimentary rocks, and overlying Phanerozoic clastic and carbon- with carbonatite–syenite complexes is just one of four significant ate sedimentary sequences (Cong, 1988; Luo et al., 1998). The Protero- metallogenic events (Table 2) that have occurred in the study areas zoic Kangding granitoid batholiths (Xu et al., 1995), located ~150 km and also include: porphyry-type Cu–Mo–Au systems controlled by north of the MD REE belt, are associated with contemporaneous arc vol- Cenozoic strike-slip faults; orogenic-type Au systems related to left-slip canic rocks in the western mobile belt of the Yangtze Craton, suggesting ductile shearing; and Pb–Zn–Ag–Cu systems controlled by Cenozoic that the Pro-Tethyan oceanic plate was subducted beneath the Craton thrusting and subsequent strike-slip faults (Table 2)(Deng et al., 2013; during the Proterozoic (Luo et al., 1998; Xu et al., 1995). A sequence of Hou and Cook, 2009). This association means that the location of the mid-Permian flood basalts with minor picrites and picritic basalts, carbonatite–syenite complexes along the giant strike-slip fault in eastern which developed on an early Permian passive continental margin, Tibet needs to be carefully examined to understand the temporal covers the western Yangtze Craton and forms a large igneous province relations between late stages of collisional orogenesis and REE minerali- (LIP) extending over an area of ~500,000 km2 (Lu, 1996; Xu et al., zation. Here, we report new SHRIMP U–Pb ages for the syenite com- 2001). This LIP is thought to have formed as a result of Emeishan mantle plexes associated with the aforementioned important REE deposits, plume activity (Chung and Jahn, 1995; Hou et al., 2006b; Lu, 1996; Xu and compare these data with the timing of movement along the adjacent et al., 2001), which also led to the formation of bauxites and gold strike-slip faults to constrain the geodynamic setting of the MD REE belt. deposits (Deng et al., 2010a,b)inareasboundedbyN–S-striking faults These data also allow us to improve the current geodynamic models for along the western margin of the Craton (Zhang et al., 1988). The the genesis of syenites along the belt during the post-collisional stage of 65–50 Ma Indian–Asian collision during the Himalayan orogenesis Indian–Asian plate convergence in eastern Tibet. (Mo et al., 2003; Yin and Harrison, 2000; Zhong et al., 2001) resulted Table 2 Four significant mineralization systems are recognized in the Tibetan orogen (from Hou and Cook, 2009; Deng et al., 2013).

Deposits Longitude/ Metallic Tonnage Grade Tectonic setting and Host rock Metallogenic Genetic type Classiﬁcation and Exploitation Data source(s) latitude commod. environment epochs ore-forming status system

I Orogenic Au Oligocene Late-collision (26–40 Ma) Laownagzhai 101°27′ Au Au: 106 T Au: 3.7–7.7 g/t Red River shear belt; the Basaltic lava, Paleozoic quartz Late-collisional Orogenic-type Au Orogenic-type Au Under Hu et al. (10) 23°54′ transform structural zone greywacke and maﬁctuff period ore-forming sys- exploitation (1995) tem Donggualin 101°26′ Au Au: 50 T Au: 5.2 g/t Red River shear belt; the Paleozoic siliceous slate, Late-collisional Orogenic-type Au Orogenic-type Au Under Hu et al. (11) 23°53′ transform structural zone meta-quartz sandstone, and period ore-forming sys- exploitation (1995) lamprophyre tem Jinchang (12) 101°45′ Au Au: 27 T Au: 1–55.5 g/t Red River shear belt; the Paleozoic tuffaceous sandstone, Late-collisional Orogenic-type Au Orogenic-type Au Under Liu et al. 23°30′ transform structural zone siltstone, and basaltic rocks, period ore-forming sys- exploitation (1993) and Hu augite peridotite tem et al. (1995) Daping (13) 102°59′ Au Au: N20 T Au: 1–32.5 g/t Red River shear belt; the Diorite, granite porphyry, Late-collisional Orogenic-type Au Orogenic-type Au Under Hu et al. 22°51′ transform structural zone lamprophyre, siliceous shale, period ore-forming sys- exploitation (1995) sandstone, limestone tem II Porphyry Cu–Mo Oligocene Late-collision (26–40 Ma) Yulong (3) 97°44′ Cu–Mo Cu:6.5 Mt Cu: 0.99% Large-scale strike-slip fault Monzonitic granite; quartz Late-collisional Porphyry Cu–Mo Porphyry-type No exploitation Tang and Luo 554 (2015) 64 Reviews Geology Ore / al. et Liu Y. 31°24′ Mo: 0.028% belt; the transform structural monzonite; Triassic sandstone period Cu–Mo ore- (1995) and zone and mudstone forming system Hou et al. (2003) Duoxiasongduo 97°55′ Cu–Mo Cu: 0.5 Mt Cu: 0.38% Large-scale strike-slip fault Alkali-feldspar granite; Late-collisional Porphyry Cu–Mo Porphyry-type No exploitation Tang and Luo (4) 31°10′ Mo: 0.04% belt, the transform structural monzonitic granite period Cu–Mo ore- (1995) and zone forming system Hou et al. (2003) Malasongduo 98°00′ Cu–Mo Cu: 1.0 Mt Cu: 0.44% Large-scale strike-slip fault Monzonitic granite; syenitic Late-collisional Porphyry Cu–Mo Porphyry-type No exploitation Tang and Luo (5) 31°00′ Mo: 0.14% belt, the transform structural granite period Cu–Mo ore- (1995) and zone forming system Hou et al. (2003) Fulongchang 99°14′ Cu–Ag– Ag: Ag: 328–547 g/t NE-striking second-order Cretaceous transitional zone Late-collisional Sediment-hosted Sediment-hosted Under Chen (2006) (6) 26°49′ Pb–Zn ∼2000 t Pb: 4.2–7.4% fault related to thrust fault; between porous sandstone and period vein-type Zn–Pb– Zn–Pb (–Cu–Ag) exploration and He et al. Cu: 0.12 Cu: 0.63–11.7% thefrontzoneinthewestern low-permeability carbonaceous Cu–Ag deposit ore-forming sys- (2009) –

12 Mt thrust nappe system; the argillite tem – transform structural zone 568 III Complex REE Oligocene– Late-collision–Post-collision (15–40 Ma) Miocene Maoniuping 101°58′ LREE 1.2 Mt REO 2.89% REO Haha strike-slip fault; the Nordmarkite with minor Late-collisional Complex-related Alkali complex- Under Yuan et al. (1) 28°23′ transform structural zone carbonatite period REE related REE ore- exploitation (1995) forming system Dalucao (2) 101°57′ LREE 0.76 Mt 5.0% REO Dalucao strike-slip fault; the Nordmarkite with minor Late-collisional Complex-related Alkali complex- Under Yuan et al. 27°12′ REO transform structural zone carbonatite period REE related REE ore- exploitation (1995) and forming system Yang et al., (1998) IV Vein-type Zn–Pb–Cu–Ag Oligocene– Late-collision–Post-collision (14–43 Ma) Miocence Sanshan– 99°18′ Zn–Pb Cu– Zn + Pb: Pb: 1.27–33.5% Fracture zones within hanging- Upper Triassic dolomitic Late-collisional Sediment-hosted Sediment-hosted Under Chen (2006) Yangzidong (7) 26°45′– Ag N0.5 Mt Zn: 1.60–3.39% wall of Huachangshan thrust limestone, breccia limestone, period vein-type Zn–Pb– Zn–Pb (–Cu–Ag) exploitation and He et al. 43′ Ag: Cu: 0.38–1.8% fault; the front zone in the sandstone and conglomerate Cu–Ag deposit ore-forming sys- (2009) N3000 t Ag: 16–189 g/t eastern thrust–nappe system; tem Cu:∼0.3 Mt the transform structural zone Jinding (8) 99°25′ Pb–Zn Pb: Pb: 1.16–2.42% Structural and litholithic trap Tertiary glutinite, argillaceous Late-collisional Sandstone- Sediment-hosted Under Xue et al. 26°24′ 2.64 Mt Zn: 8.32–10 52% and dome in the eastern dolomite, argillaceous siltstone, period hosted Zn–Pb de- Zn–Pb (–Cu–Ag) exploitation (2007) and He Zn: Ag: 12.5–126 g/t thrust–nappe system; the quartz sandstone, siltstone posit ore-forming sys- et al. (2009) 12.84 Mt transform structural zone tem Ag: 1722 t 557 558 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568

Fig. 2. (A). Cenozoic tectonic map of eastern Tibet (Wang et al., 2001b), showing the location of the Himalayan potassic rock belt (Chung et al., 1998; Zhang and Xie, 1997), shoshonitic lamprophyres (Guo et al., 2005) and carbonatite–syenite complexes (Yuan et al., 1995), which form a Cenozoic discontinuous igneous province in the EIAZ. (B). Sketch tectonic map showing distribution of the Himalayan carbonatite–alkalic complexes controlled by reactivated faults in western Sichuan. Modified from Yuan et al. (1995). in the reactivation of the western margin of the Yangtze Craton and the and peaking at 35 Ma (Chung et al., 1998; Guo et al., 2005; Hou et al., formation of the N–S-striking Jinpingshan Orogen (collisional belt) 2003; Wang et al., 2001a,b; Zhang and Xie, 1997). Monzogranite stocks within the EIACZ (Fig. 1; Luo et al., 1998), together with a series of in the potassic belt are associated with Cu mineralization, including the Cenozoic strike-slip faults (Fig. 2) within the EIACZ to accommodate Himalayan Yulong porphyry Cu belt in eastern Tibet (Hou et al., 2003), the strain produced by this collision. These strike-slip faults include, whereas carbonatite–syenite complexes are associated with REE miner- from west to east, the Jiali and Gaoligong faults around the eastern alization (Tian, 2005) such as the MD REE belt in western Sichuan Himalayan syntaxis, the Batang–Lijiang Fault in the northern part, the (Fig. 1). The O\H\C isotope data from gangue calcite, fluorite, and Ailaoshan–Red River Fault (ASRR) in the southern part, and the quartz indicate that the fluids were of magmatic origin, but that they Xianshuihe and Xiaojiang faults within the Yangtze Craton (Fig. 1). were mixed with an external fluid mainly of meteoric origin (Hou Cenozoic deformation associated with this faulting resulted in et al., 2009). Such fluids were recognized not only in the REE deposits Eocene–Oligocene (55–32 Ma) transpression, early–middle Miocene along the EIACZ, but also in deposits hosting Au and Cu mineralization (26–17 Ma) transtension, and late Neogene–Quaternary E–W extension (Deng et al., 2009, 2011) within the EIACZ (Wang et al., 2001a,b). Himalayan magmatism in the EIACZ led to the formation of a semi-continuous potassic igneous prov- 3. Spatial and temporal distribution of syenite magmatism ince in southwestern China (Guo et al., 2005). From west to east, this province encompasses (1) a 1000-km-long belt of potassic rocks associ- Carbonatite–syenite complexes in western Sichuan form the eastern ated with early–middle Cenozoic pull-apart basins developed along a part of the Cenozoic igneous province discussed above (Fig. 1). These narrow belt parallel to the Nanqian Thrust, the Batang–Lijiang Fault, alkaline rocks intruded the Proterozoic crystalline basement and overly- and the Red River shear zone (RRSZ; Zhang and Xie, 1997; Wang ing Paleozoic–Mesozoic volcano-sedimentary sequence, forming a nar- et al., 2001a,b; Hou et al., 2003); (2) a 50,000-km2 calc-alkaline row, N–S trending belt hosting REE mineralization. The belt is bordered shoshonitic-lamprophyre district to the east of the RRSZ (Guo et al., by N–S-oriented strike-slip faults (Figs. 1 and 2), and the extent of 2005; Luo and Yu, 2001); and (3) a 270-km-long belt of carbonatite– irregularly-shaped individual complexes within the belt is controlled syenite complexes within the western part of Sichuan Province, by second-order strike-slip or transtensional faults (Fig. 2). These bounded by the N–S-striking Yalongjiang and Anninghe faults, which complexes are dominated by syenite bodies with minor carbonatite were reactivated during the Indian–Asian collision (Fig. 2). All this sills and dikes. The entire belt can be divided into southern and northern magmatism occurred over a short period of time, from 40 to 24 Ma parts based on the distribution and ages of REE deposits and the ages of Table 3 SHRIMP zircon analyses of the syenites in Mianing–Dechang REE belt.

206 206 206 238 207 206 207 235 208 232 207 ⁎ 206 ⁎ 207 ⁎ 235 206 ⁎ 238 Spot Pbc(%) U (ppm) Th (ppm) Th/U Pb*(ppm) Pb/ U Pb/ Pb Pb/ U Pb/ Th Pb / Pb ±% Pb / U±% Pb / U±%Degreeof concordance Age/Ma Age/Ma Age/Ma Age/Ma

DLC11-1-1 (syenite, Dalucao deposit, northern parts of the Mianning–Dechang REE belt) 1 8.91 916 1243 1.4 1.63 12.16 ±0.25 −2270 ±2900 5.77 ±4.20 10.5 ±1.2 0.022 73 0.0057 73 0.001888 2.1 2 20.87 430 371 0.89 0.761 10.51 ±0.62 −16.38 ±12.1 4.6 ±4.7 −0.072 73 −0.016 73 0.001631 5.9 3 5.82 1101 885 0.83 1.87 12 ±0.23 −830 ±1200 8.69 ±3.64 12.5 ±1.7 0.034 42 0.0086 42 0.001864 1.9 4 9.73 536 456 0.88 0.991 12.5 ±0.35 880 ±680 18.41 ±6.02 16.7 ±2.6 0.068 33 0.0183 33 0.001941 2.8 0.01 5 5.85 549 406 0.76 0.969 12.46 ±0.31 481 ±680 15.22 ±4.68 15.1 ±2.4 0.057 31 0.0151 31 0.001935 2.5 0.03 6 6.89 655 593 0.93 1.12 11.95 ±0.34 −1050 ±2100 8.09 ±5.64 12.1 ±2.3 0.031 70 0.008 70 0.001856 2.9 7 1.57 948 883 0.96 1.6 12.43 ±0.18 676 ±280 16.62 ±2.14 14.69 ±0.92 0.0621 13 0.0165 13 0.001931 1.4 0.02 8 11.4 513 408 0.82 0.85 11.02 ±0.38 8.4 ±2.9 0.001711 3.5 9 10 577 453 0.81 0.984 11.51 ±0.33 7.8 ±2.6 0.001787 2.9 10 3.55 1774 1246 0.73 2.99 12.17 ±0.12 −314 ±380 10.71 ±1.60 12.63 ±0.90 0.0406 15 0.0106 15 0.00189 10 11 5.09 658 677 1.06 1.17 12.6 ±0.31 −790 ±1300 9.30 ±4.26 13.1 ±1.6 0.034 46 0.0092 46 0.001956 2.5 554 (2015) 64 Reviews Geology Ore / al. et Liu Y. 12 8.2 589 656 1.15 1.03 12.04 ±0.26 −1210 ±1700 7.69 ±4.29 11.2 ±1.4 0.03 56 0.0076 56 0.00187 2.2 13 14.68 140 25 0.19 0.269 12.3 ±1.7 72 ±59 0.00191 14 14 38.50 118.81 85.89 0.75 0.26 10.1 ±1.9 0.00157 19 15 10.12 546 465 0.88 0.951 11.74 ±0.41 10.4 ±3.0 0.001823 3.5 16 8.63 808 878 1.12 1.37 11.58 ±0.30 9.6 ±1.6 0.001798 2.6

Error in standard calibration was 0.24% DLC11-2 (syenite, Dalucao deposit, northern parts of the Mianning–Dechang REE belt) 5 4.39 1186 869 0.76 1.86 11.23 ±0.19 −619 ±660 8.80 ±2.10 10.7 ±1.2 0.0362 24 0.0087 24 0.001744 1.7 7 12.5 1047 515 0.51 1.68 10.53 ±0.45 −8.57 ± − 8.09 −0.037 94 −0.0084 94 0.001635 4.2 9 3.82 1757 1650 0.97 2.66 10.9 ±0.20 −1470 ±1400 6.38 ±2.73 9 ±1.1 0.027 43 0.0063 43 0.001692 1.9 10 30.99 192 71 0.38 0.374 10.1 ±1.4 0.00157 14 11 9.74 923 652 0.73 1.61 11.77 ±0.43 9.5 ±3.6 0.001827 3.6 12 46.29 66 31 0.49 0.198 12.1 ±4.7 117 ±64 0.00188 39 13 7.14 1179 1694 1.48 1.6 9.43 ±0.39 8.1 ±1.3 0.001464 4.1 – 14 16.48 1204 1608 1.38 1.53 7.97 ±0.41 5.5 ±1.9 0.001238 5.1 568 15 29.45 167 72 0.44 0.337 10.7 ±1.7 0.00166 16 16 3.7 1489 1070 0.74 2.39 11.59 ±0.21 −886 ±960 8.29 ±2.72 11.8 ±1.4 0.033 33 0.0082 33 0.0018 1.8 17 47.6 116 24 0.21 0.296 10 ±3.5 0.00155 35 32 7.38 286 135 0.49 0.574 13.94 ±0.51 1626 ±480 29.91 ±7.66 47.8 ±6.3 0.1 26 0.0299 26 0.002165 3.7 0.01 18 9.91 1222 1241 1.05 1.87 10.35 ±0.32 6.8 ±1.9 0.001606 3.1 19 9.71 1053 718 0.7 1.84 11.82 ±0.40 −380 ±1700 10.10 ±6.53 13.1 ±3.6 0.04 65 0.01 65 0.001835 3.4 20 22.31 312 63 0.21 0.595 11.09 ±0.48 −19 ±16 0.001723 4.3 21 19.64 80 19 0.25 0.189 14.3 ±2.5 2500 ±1300 49.54 ±36.75 188 ±65 0.16 74 0.05 76 0.00222 17 0.01 22 4.5 1625 2960 1.88 2.55 11.24 ±0.24 −1310 ±1500 6.98 ±3.20 10.61 ±0.69 0.029 46 0.0069 46 0.001745 2.1 23 7.04 946 648 0.71 1.61 11.89 ±0.43 −900 ±2300 8.39 ±6.77 10.9 ±3.6 0.033 80 0.0083 81 0.001847 3.7 25 13.83 917 1006 1.13 1.56 10.98 ±0.46 8.3 ±2.6 0.001704 4.2 26 18.54 368 312 0.88 0.741 12.3 ±1.1 13.5 ±8.1 0.00191 9.3 27 5.57 1025 764 0.77 1.79 12.33 ±0.29 −770 ±1100 10.5 ±1.9 0.034 40 0.009 41 0.001915 2.3 28 21.76 228 220 1 0.511 13.2 ±1.4 27 ±10 0.00205 10 29 3.61 1636 1257 0.79 2.59 11.45 ±0.23 −529 ±850 10.9 ±1.4 0.037 32 0.0092 32 0.001777 2 33 10.22 826 1675 2.1 1.38 11.23 ±0.42 9.6 ±1.3 0.001744 3.8

(continued on next page) 559 560

Table 3 (continued) 206 206 206 238 207 206 207 235 208 232 207 ⁎ 206 ⁎ 207 ⁎ 235 206 ⁎ 238 Spot Pbc(%) U (ppm) Th (ppm) Th/U Pb*(ppm) Pb/ U Pb/ Pb Pb/ U Pb/ Th Pb / Pb ±% Pb / U±% Pb / U±%Degreeof concordance Age/Ma Age/Ma Age/Ma Age/Ma

Error in standard calibration was 0.33% MNP11-1-18 (syenite, Maoniuping deposit, southern parts of the Mianning–Dechang REE belt) 1 0.51 5663 5711 1.04 18.9 24.82 ±0.11 2 ±88 24.59 ±0.90 23.49 ±0.39 0.0461 3.7 0.02451 3.7 0.003858 0.44 12.41 7 1.77 3047 3608 1.22 9.64 23.27 ±0.15 −496 ±250 19.01 ±1.75 21.7 ±0.63 0.0378 9.3 0.0189 9.3 0.003617 0.65 9 0.09 2450 1461 0.62 7.85 23.97 ±0.15 131 ±130 25.07 ±1.39 23.4 ±0.85 0.0487 5.6 0.025 5.6 0.003726 0.61 0.18 11 8.81 13,578 5867 0.45 47.5 23.88 ±0.42 441 ±630 28.53 ±7.88 26.5 ±6.6 0.056 28 0.0285 28 0.003711 1.8 0.05 13 0.29 3501 1944 0.57 10.7 22.78 ±0.14 200 ±120 24.58 ±1.21 24.13 ±0.86 0.0501 5 0.0245 5 0.003539 0.62 0.11 15 1.66 3051 2715 0.92 9.29 22.44 ±0.17 −275 ±260 19.91 ±1.97 22.43 ±0.92 0.0412 10 0.0198 10 0.003487 0.75

MNP11-1-19 (syenite, Maoniuping deposit, southern parts of the Mianning–Dechang REE belt) 2 0.86 4780 5587 1.21 13.4 20.84 ±0.49 −119 ±160 19.71 ±1.33 19.34 ±0.65 0.0439 6.4 0.0196 6.8 0.003238 2.4 3 1.27 5031 2811 0.58 14.5 21.31 ±0.50 −95 ±200 20.31 ±1.69 20.6 ±1.2 0.0443 8.1 0.0202 8.4 0.003311 2.3 4 0.91 3309 3400 1.06 9.99 22.41 ±0.52 −106 ±110 21.30 ±1.05 21.75 ±0.68 0.0441 4.5 0.0212 5 0.003482 2.3

5 0 3298 3165 0.99 9.46 21.5 ±0.50 241 ±83 23.59 ±1.00 20.41 ±0.65 0.051 3.6 0.0235 4.3 0.003341 2.3 0.09 554 (2015) 64 Reviews Geology Ore / al. et Liu Y. 6 0.57 4563 5797 1.31 13.2 21.48 ±0.52 −32 ±220 21.00 ±2.00 20.15 ±0.73 0.0454 9.3 0.0209 9.6 0.003337 2.4 7 0.75 2830 1662 0.61 7.84 20.61 ±0.49 −249 ±190 18.51 ±1.41 19.39 ±0.98 0.0416 7.3 0.0184 7.7 0.003202 2.4 10 1 2976 2350 0.82 8.86 22.08 ±0.51 101 ±110 22.79 ±1.19 20.77 ±0.75 0.048 4.8 0.0227 5.3 0.003431 2.3 0.22 12 0.5 4438 4628 1.08 13.1 21.94 ±0.53 71 ±93 22.39 ±1.02 21.15 ±0.63 0.0474 3.9 0.0223 4.6 0.003409 2.4 0.31 13 1.26 2959 4000 1.4 8.36 20.91 ±0.49 22 ±150 20.90 ±1.37 19.71 ±0.93 0.0465 6.1 0.0208 6.6 0.003249 2.3 0.95 14 0.58 3803 4041 1.1 11.1 21.76 ±0.52 398 ±87 25.57 ±1.14 20.94 ±0.88 0.0546 3.9 0.0255 4.5 0.003382 2.4 0.05 15 3.7 2660 2064 0.8 7.55 20.48 ±0.53 −281 ±580 18.11 ±4.13 19 ±1.9 0.0411 23 0.018 23 0.003182 2.6 16 0.56 2863 3600 1.3 7.87 20.48 ±0.48 −245 ±170 18.41 ±1.28 18.02 ±0.65 0.0417 6.6 0.0183 7 0.003182 2.4

Error in standard calibration was 0.30% LZ121 (syenite, Lizhuang deposit, southern parts of the Mianning–Dechang REE belt) 1 0.09 2892 3202 1.14 10.7 27.71 ±0.36 −227 ±94 25.01 ±0.99 17.9 ±1.4 0.042 3.7 0.02494 4 0.004307 1.3 2 0.27 1594 1423 0.92 5.84 27.33 ±0.47 31 ±270 27.35 ±2.97 23.3 ±1.9 0.0466 11 0.0273 11 0.004249 1.7 0.88 4 0.07 1152 1804 1.62 4.29 27.84 ±0.39 −594 ±310 21.90 ±2.60 17.4 ±1.5 0.0365 12 0.0218 12 0.004328 1.4 5 1.20 76 48 0.66 1.5 140.4 ±3.9 −900 ±1500 95.85 ±46.65 91 ±29 0.033 51 0.099 51 0.02201 2.8

− – 8 2.28 892 1111 1.29 3.29 26.99 ±0.40 1109 ±340 17.72 ±1.93 19.02 ±0.91 0.0305 11 0.0176 11 0.004195 1.5 568 9 1.04 1685 2468 1.51 6.15 27.05 ±0.38 −354 ±310 23.29 ±2.76 22.1 ±1.6 0.04 12 0.0232 12 0.004205 1.4

Error in standard calibration was 0.41% DLS116 (syenite, Diaoloushan deposit, southern parts of the Mianning–Dechang REE belt) 1 6.75 510 1455 2.95 1.89 25.92 ±0.85 −2380 ±4100 12.11 ±12.0 24.5 ±1.6 0.021 99 0.012 99 0.00403 3.3 2 1.69 2182 1696 0.8 7.72 26.07 ±0.52 −345 ±240 22.49 ±2.07 24.9 ±1.2 0.0401 9.1 0.0224 9.3 0.004052 2 4 1.75 1228 644 0.54 4.55 27.27 ±0.64 70 ±240 27.74 ±2.74 28.3 ±2.1 0.0474 10 0.0277 10 0.00424 2.4 0.39 5 2.09 548 1327 2.5 2 26.83 ±0.59 221 ±230 29.13 ±2.87 26.21 ±0.88 0.0506 9.8 0.0291 10 0.00417 2.2 0.12 6 1.74 1308 700 0.55 4.79 26.96 ±0.55 −80 ±230 25.77 ±2.47 29.1 ±1.9 0.0445 9.5 0.0257 9.7 0.004191 2.1 8 2.28 1979 1380 0.72 7.15 26.43 ±0.54 −384 ±350 22.49 ±3.11 27 ±1.8 0.0395 14 0.0224 14 0.004108 2.1 10 1.62 1142 656 0.59 4.13 26.62 ±0.59 −82 ±440 25.47 ±4.53 28.8 ±3.2 0.0445 18 0.0254 18 0.004138 2.2 11 2.35 1556 788 0.52 5.72 26.86 ±0.60 −543 ±620 21.50 ±4.89 25.9 ±3.7 0.0372 23 0.0214 23 0.004176 2.2 12 3.25 1256 675 0.55 4.59 26.45 ±0.58 111 ±370 27.45 ±4.33 29 ±3.1 0.0482 16 0.0274 16 0.004112 2.2 0.24 13 0.91 2103 1738 0.85 7.89 27.84 ±0.49 123 ±80 28.93 ±1.08 28.65 ±0.77 0.0485 3.4 0.0289 3.8 0.004327 1.8 0.23 14 7.23 1391 845 0.63 5.45 27.19 ±0.68 210 ±650 29.32 ±8.09 27.4 ±5.3 0.05 28 0.0293 28 0.00423 2.5 0.13 16 2.12 1674 1088 0.67 6.19 27.1 ±0.52 29 ±290 27.15 ±3.21 27.1 ±1.9 0.0466 12 0.0271 12 0.004213 1.9 0.93

Error in standard calibration was 0.85%. ⁎ Errors are 1-sigma; Pbc and Pb indicate the common and radiogenic portions, respectively. Common Pb corrected using measured 204 Pb. Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568 561

Fig. 3. Cathodoluminescence images of zircon grains from DLC11-1-1 (Daluocao). The marked SHRIMP spot numbers, and 207Pb-corrected 206Pb/238U ages correspond to those in Table 3.

Fig. 4. Cathodoluminescence images of zircon grains from sample DLC11-2 (Daluocao deposit). The marked SHRIMP spot numbers, and 207Pb-corrected 206Pb/238Uagescorrespondto those in Table 3. 562 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568

Fig. 5. SHRIMP U–Pb zircon age diagram for syenites from Daluocao (A and B), Maoniuping (C and D), Diaoloushan (E) and Lizhuang (F). individual complexes. The southern part of the belt contains a zircons from syenite; 40.3 ± 0.70 Ma measured by K–Ar method on carbonatite–syenite complex that is controlled by the Dalucao strike- biotite separated from bastnäsite–aegirine–augite–ﬂuorite–barite and slip fault (Fig. 2B), and this complex intruded a Proterozoic quartz 31.7 ± 0.70 Ma measured by the same method on arfvedsonite from diorite pluton with a SHRIMP U–Pb zircon age of 764 Ma (Tian et al., bastnäsite–barite–calcite veins. A syenite sample from the Muluozhai 2008a). The complex consists of syenite stocks, carbonatite sills and deposit yielded a microcline 40Ar/39Ar age of 31.2 ± 0.56 Ma (Tian two REE-enriched breccia pipes (Yang et al., 1998). Carbonatite and et al., 2006)(Table 1). Microcline from syenite from the Lizhuang com- nordmarkite units in this area yield zircon SHRIMP U–Pb zircon ages plex yielded a younger 40Ar/39Ar age of 27.1 Ma, which is a total fusion of 12.99 ± 0.94 and 14.53 ± 0.31 Ma, respectively (Tian et al., 2008a). value, rather than a plateau age (Tian, 2005; Tian et al., 2008b). The northern part of the belt contains the Maoniuping, Lizhuang, and Muluozhai complexes, all oriented approximately N–S(Fig. 2). These 4. Sampling and analytical methods complexes are dominated by syenite bodies with minor carbonatite sills and dikes. Four ages have been reported for the Maoniuping deposit Zircons were separated from fresh syenite samples from the by Yuan et al. (1995): 12.2 Ma and 22.4 Ma, acquired by ID-TIMS on Dalucao, Maoniuping, Lizhuang and Diaoloushan deposits. Diaoloushan Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568 563

Fig. 6. Cathodoluminescence images of zircon grains from the Maoniuping deposit. The marked SHRIMP spot numbers, and 207Pb-corrected 206Pb/238U ages correspond to those in Table 3. is one of the three orebodies in the Muluozhai deposit, with the Instrumental conditions and measurement procedures were similar to other two being Fangjiabao and Zhengjialiangzi. Zircon separation, those reported previously (Black et al., 2003; Compston et al., 1992; cathodoluminescence (CL) imaging and U–Th–Pb isotope measure- Stern and Amelin, 2003), including measurements produced in the ments were all carried out at the Beijing SHRIMP Center, Chinese same facility (Deng et al., 2010a; Sun et al., 2010; Zhang et al., 2008; Academy of Geological Sciences (CAGS). Zircon grains were extracted Zheng et al., 2012). The primary O2− ion beam at the required intensity from rock samples using the conventional procedures including rock ranged between 5 and 7 nA, and done using a spot size between 25 and crushing, sieving, elutriation, drying, dressing by magnetic, electromag- 30 μm during the analysis. Each spot was rastered for 3–4 min prior to netic and heavy liquid separation, and hand picking under a binocular analysis to remove surﬁcial common Pb and contaminants. Five scans 196 204 microscope. Zircon grains were then mounted onto a double-sided through nine mass stations, including Zr2O, Pb, background, adhesive tape and enclosed in an epoxy resin disk with a diameter 206Pb, 207Pb, 208Pb, 238U, 248ThO and 254UO, were acquired for the stan- of 2.5 cm, along with TEMORA 1 reference zircon (206Pb/238Uage= dards. Reference zircon M257 was analyzed for elemental abundance 416.8±1.3Ma)andM257(U=840ppm)(Black et al., 2003; calibration. TEMORA 1 was analyzed for calibration of 206Pb/238Uafter Nasdala et al., 2008). The morphology of zircon crystals was examined every 3–4 analyses on unknowns. Common-Pb correction was referred in both transmitted and reﬂected light, and images were taken using to the measured 204Pb abundances. The data reduction was performed an optical microscope and a CL imaging system. CL image reveal differ- using the SQUID 1.0 (Ludwig, 2001) and ISOPLOT/Ex software ences in the abundances of some trace elements (U, Y, Dy and Tb) (Ludwig, 2003). Errors in individual analyses are based on the counting and/or defects in the crystal lattice of zircon (e.g., Wu and Zheng, statistics and are quoted at the 1σ level, whereas those for the pooled 2004). The CL images were acquired using a HITACHI S3000-N scanning analyses are quoted at the 2σ level. Because of small amounts of 207Pb electron microscope equipped with a Robinson backscattered-electron formed in young (i.e. b800 Ma) zircons, which results in low count detector and Gatan Chroma CL imaging system prior to U–Th–Pb iso- rates and high analytical uncertainties, the determination of the ages tope measurements. All U–Th–Pb analyses were done using a SHRIMP for young zircons has to be based primary on their 206Pb/238U ratios. II instrument. Inter-element fractionation during zircon ion emission SHRIMP U–Pb data of these zircon analyses are summarized in Table 3. was used to monitor analytical conditions relative to the TEMORA 1 Zircons separated from syenite sample DLC11-1-1 from the Dalucao reference zircon (Black et al., 2003), with this reference sample being deposit are 100–200 μmwide,200–400 μm long, euhedral and prismatic, measured once every three unknowns to monitor the stability of and show oscillatory zoning (Fig. 3), indicating a magmatic origin. Fifteen the instrument and to guarantee the production of reliable results. of these crystals were analyzed in this study, and the resulting SHRIMP 564 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568

U–Pb data are summarized in Table 3. These analyses yielded a concor- Zircons from syenite sample DLS116 from the Diaoloushan orebody dant age of 12.13 ± 0.19 Ma (n = 15, MSWD = 1.7; Fig. 5A). are 20–70 μm wide, 100–150 μm long, euhedral, prismatic, and show Sample DLC11-2 was collected at the same location in the Dalucao oscillatory zoning, indicating a magmatic origin (Fig. 7). Twelve crystals deposit as DLC11-1-1. Zircons in DLC11-2 are 70–200 μmwide, from this sample were analyzed and the results are summarized in 100–200 μm long, euhedral and prismatic, and also show oscillatory Table 3; these analyses yielded a concordant age of 26.77 ± 0.32 Ma zoning (Fig. 4). In comparison with the DLC11-1-1 zircons, those in (n = 12, MSWD = 1.18; Fig. 5E). DLC11-2 have a brighter irregular core suggestive of zircon alteration Zircons from syenite sample LZ121 from the Lizhuang deposit are by infiltrating fluids. Twenty-four analyses of 16 zircons from this 80–200 μm wide, 160–200 μm long, euhedral, prismatic, and show oscil- sample were obtained (Table 3). Among these analyses, three of the latory zoning, indicating a magmatic origin (Fig. 8). Six SHRIMP U–Pb twenty-four were discarded because they are not discordant and they analyses of six zircons from this sample are summarized in Table 3. are DLC11-2-13, DLC11-2-14 and DLC11-2-32 analyses. The remaining One of the crystals gave an age of 140 Ma (see Section 5.1), and the re- data (Table 3) yielded a concordant age of 11.32 ± 0.23 Ma (n = 21, maining five analyses yielded a concordant age of 27.41 ± 0.35 Ma MSWD = 2.1; Fig. 5B). (MSWD = 0.95; Fig. 5F). Zircons from syenite samples MNP11-1-18 and MNP11-1-19 from the Maoniuping deposit are 50–150 μmwideand100–300 μmlong, generally colorless, euhedral (with a small number of prismatic crys- 5. Discussion tals), and show oscillatory zoning (Fig. 6). These features are similar to those seen in typical zircon from granites elsewhere and are indicative 5.1. Ages of syenite complexes in the MD REE belt and implications for the of a magmatic origin (Hoskin and Black, 2000). The results of SHRIMP timing of REE mineralization U–Pb analyses of seven crystals from sample MNP11-1-18 are listed in Table 3; these data yielded a concordant age of 22.81 ± 0.31 Ma The new high-precision U–Pb data presented above provide age (n = 7, MSWD = 1.6; Fig. 5C). useful temporal constraints for the syenite magmatism in the MD belt. Twelve zircons from sample MNP11-1-19 (Table 3) also yielded a The new results can be separated into two groups: 11–12 Ma in concordant age of 21.3 ± 0.40 Ma (n = 12, MSWD = 1.7; Figs. 5Dand6). the southern part of the belt, which includes the Dalucao deposit, and

Fig. 7. Cathodoluminescence images of zircon grains from the Diaoloushan orebody (Muluozhai). The marked SHRIMP spot numbers, and 207Pb-corrected 206Pb/238Uagescorrespondto those in Table 3. Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568 565

21–27 Ma in the northern part, which comprises the Maoniuping and has a younger concordant age than DLC11-1-1 (12.13 ± 0.19 Ma), Lizhuang deposits and the Diaoloushan orebody. These ages indicate whereas MNP11-1-19 (21.3 ± 0.4 Ma) has a younger concordant age younging of magmatism from north to south along the MD belt. Zircon than MNP11-1-18 (22.81 ± 0.31). Both DLC11-1-1 and DLC11-2 were from the Dalucao deposit yielded ages of 11.32 ± 0.23 and 12.13 ± sampled from ore body No.1 in the Dalucao deposit, and MNP11-1-18 0.19 Ma, which are similar to the SHRIMP U–Pb ages of zircon from and MNP11-1-19 samples also come from the same area as each carbonatites and nordmarkites in this area (12.99 ± 0.94 and 14.53 ± other. On the basis of the CL images and SHRIMP U–Pb results, the youn- 0.31 Ma, respectively; Tian et al., 2008a). Given that the analyses ger ages of DLC11-2 and MNP11-1-19 may be explained by alteration of obtained in this study were performed using the same method and some zircons by fluid infiltration. For example, among the examined zir- instrument, and yielded similar ages, we conclude that the Dalucao cons in sample DLC11-1-1, gains of DLC11-1-1-14 and DLC11-1-1-15 alkaline intrusions formed at ~12 Ma. give somewhat younger ages of 10.1 and 11.74 Ma, respectively, com- The syenite samples from the Maoniuping deposit yielded ages of pared with the unaltered grains. However, in comparison with sample 22.81 ± 0.31 and 21.3 ± 0.4 Ma, both of which are consistent with DLC11-1-1, more zircons from DLC11-2 appear to have been altered the previously determined U–Pb age of 22.4 Ma for this syenite (Yuan and thus give younger ages (Fig. 4), explaining why the concordant et al., 1995), but inconsistent with the 12.2 Ma age reported by the age of DLC11-2 is younger. Thus, we consider the age of 12.13 ± same authors (Table 1). The age of 12.2 Ma is coeval with the intrusion 0.19 Ma to be the more reliable estimate for the Dalucao syenite. of syenites at the Dalucao deposit. However, the ages reported by Yuan The specific geological setting of syenites, carbonatites and REE min- et al. (1995) were obtained by ID-TIMS, and cannot represent the eralization may have led to slight differences in zircon ages among sye- precise ages of the Maoniuping syenite. There is no certainty about nite samples from the same locality. Syenites in the MD REE belt are how the data of Yuan et al. (1995) should be interpreted. The age of associated with mineralized veins and exhibit evidence of alteration 12.2 Ma was assumed to correspond to late-stage evolution of the sye- by ore-forming fluids. It is possible that all these rocks were altered to nite and the onset of mineralization, whereas the age of 22.4 Ma, consis- some degree. For example, in the Dalucao deposit, syenites are com- tent with the ages obtained in the present study, was regarded as having monly crosscut by quartz–barite–celestite–calcite veins in orebody no clear geological significance and requiring further study (Yuan, et al., No. 1 (Fig. 9A) or altered by a late-stage ore-forming fluid derived 1995). By comparison, the syenite from the Diaoloushan orebody from magmatic and meteoric sources (Fig. 9B). In the Maoniuping yielded a weighted SHRIMP U–Pb zircon age of 26.77 ± 0.32 Ma, deposit, syenites either occur in association with quartz–barite– which is ~4 Ma younger than a microcline Ar–Ar age of 31.2 Ma for celestite–calcite veins and carbonatites (Fig. 9C), or show evidence of this syenite, possibly as a result of the difference in dating methods alteration by ore-forming fluids (Fig. 9D). At Lizhuang, altered syenite used. The syenite from the Lizhuang deposit analyzed in the present occurs at the top of an orebody (Fig. 8E) and fresh syenite in the lower work yielded an age of 27.41 ± 0.35 Ma, which is consistent with the part of the deposit (Fig. 8F). In this study, we attempted to date zircons previously determined microcline Ar–Ar age of 27.1 Ma (Tian et al., only from unaltered syenites, but despite these efforts, some zircons ex- 2008b). Despite the similarity, 27.41 ± 0.35 Ma is a more reliable amined in the present study were perceptibly affected by late-stage value because of the higher closure temperature of zircon and precision fluids and show younger ages than the unaltered ones, as exemplified of our data. by samples DLC11-2 and MNP11-1-19 discussed above. Where two samples of syenite from the same deposit were studied, Five analyses of zircons from sample LZ121 yielded a concordant the data show slight age variations. Samples DLC11-2 (11.32 ± 0.23 Ma) age of 27.41 ± 0.35 Ma, and a single grain gave an age of 140 Ma. This

Fig. 8. Cathodoluminescence images of zircon grains from the Lizhuang deposit. The marked SHRIMP spot numbers, and 207Pb-corrected 206Pb/238U ages correspond to those in Table 3. 566 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568 older grain is probably a xenocryst incorporated into as syenitic magma 5.2. Constraints on the regional geological setting during its ascent. Although there is no geological evidence to support the existence of episodes of syenitic magmatism beginning on the Cre- The present study provides the ﬁrst systematic set of age data for taceous, the possibility cannot be ruled out. syenites within the MD belt, including precise ages for the Maoniuping The Tibetan Orogen has a complex history, including syn-collisional deposit, for which reliable data were previously lacking. The new data (65–41 Ma), late-collisional (40–26 Ma) and post-collisional (25–0Ma) presented here not only constrain the timing of formation of the MD stage (Hou and Cook, 2009). The new syenite ages for the MD belt belt, but also place constraints on the evolution of the geological setting presented here (27–12 Ma) further support the conclusion that strike- of the EIACZ. Eastern Tibet contains a number of regional strike-slip slip shearing within the EIACZ occurred between 27 and 12 Ma, faults (see Section 2), which have accommodated strain related to the i.e. during the late-collisional and post-collisional stages of orogenesis. Indian–Asian collision. The results of previous studies (Cao et al., The formation of carbonatites as a result of liquid immiscibility could 2011), combined with the geochronological data presented here, sug- generate large volumes of REE- and F-rich ﬂuids that would tend to es- gest that the lateral strike-slip shearing along the ASRR shear zone in cape from the carbonatite–syenite magma system (Hou et al., 2006a,b), southeastern Tibet (Fig. 1) was initiated at ~31 Ma and culminated be- indicating that the syenite emplacement ages (12–27 Ma) represent the tween ~27 and 21 Ma. This indicates that the 12–27 Ma ages of syenites maximum ages of carbonatites and REE mineralization in the MD belt. in the northern part of the MD belt (Maoniuping, Lizhuang and These new ages are consistent with the previously published ages for Muluozhai) is coeval with strike-slip shearing along the ASRR. However, mineralization at the Dalucao deposit (13.33 ± 0.41 Ma and 12.95 ± the chronology of syenite in the Dalucao deposit in the southern part of 0.22 Ma measured on muscovite by Ar–Ar method), and the Lizhuang the MD belt indicates that shearing along strike-slip faults in that area deposit (28.5 Ma, a Re–Os model age for molybdenite) (Tian et al., may have continued until at least 12 Ma, and possibly longer. 2008b). This consistency of ages lends further support to the accuracy Strike-slip faulting in the eastern Tibet is only one of several struc- of the SHRIMP U–Pb data presented here (Table 1). tural responses to the Indian–Asian collision that occurred 55–60 Ma

Fig. 9. Geological occurrence of syenites in MD belt. (A) Syenite in orebody No. 1 in the Dalucao deposit with barite–fluorite–quartz coarse-grained veins crosscutting syenite; (B) altered syenite in orebody No. 2 in the Dalucao deposit; (C) barite–fluorite–quartz vein in syenite in the Maoniuping deposit; (D) bastnäsite–aegirine–augite–fluorite–barite coarse-grained mineral veins in the Maoniuping deposit; (E) altered syenite in the Lizhuang REE deposit; and (F) fresh syenite in the lower part of the Lizhuang REE deposit. Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568 567 ago. Geomorphologically, high topography in eastern Tibet is another Oligocene probably caused decompressional melting of the EMI–EMII response within the same time together with strike-slip faulting. The mantle beneath the EIACZ. The same type of tectonic transition has high topography in eastern Tibet is thought to have developed when been invoked to explain development of ore-bearing magmas and asso- deep crust beneath the central Tibetan Plateau flowed toward the pla- ciated Cu mineralization in Tongling, Anhui Province, China (Deng et al., teau margin, causing crustal thickening and surface uplift (Clark and 2011). Royden, 2000; Royden et al., 1997). Thermochronology was adopted and rocks exposed in a section that stretches vertically over 3 km 6. Conclusions adjacent to the Sichuan Basin were selected to measure the cooling his- tories (Wang et al., 2012). Then, thermal model was set up as fellows. New SHRIMP U–Pb zircon data yielded crystallization ages of During the early Cenozoic, plateau margin was subject to slow and 12.13 ± 0.19 and 11.32 ± 0.23 Ma for the Dalucao syenite, 22.81 ± steady exhumation. However, two phases of rapid exhumation began 0.31 and 21.3 ± 0.4 Ma for the Maoniuping syenite, and 27.41 ± at 30–25 million years and the other started at 10–15 million years 0.35 Ma for the Lizhuang syenite. Previously obtained mineralization ago (Wang et al., 2012). These phases correspond, respectively, to the ages, combined with the new ages presented here, indicate that both late- and post-collisional stages of orogenesis (Hou and Cook, 2009). syenites and the associated REE mineralization were formed nearly In the MD belt, the earlier-formed faults bordering the Permian paleorift contemporaneously at 20–30 Ma in the northern part of the MD belt zone were reactivated as strike-slip faults, which may have facilitated and at 11–12 Ma in its southern part. These ages indicate late- to post- the emplacement of syenites at Dalucao at 11–12 Ma and Maoniuping, collisional development of the carbonatite–syenite complexes. Lizhuang and Muluozhai at 21–27 Ma. The ages of syenites along the MD belt are consistent with the The ages obtained in the present work improve our understanding of timing of strike-slip shearing along the ASRR, suggesting concurrent the geodynamic setting of eastern Tibet. Although the MD belt is located strike-slip faulting in the MD belt and strike-slip faulting elsewhere in a Permian paleorift zone, it actually developed in a collisional orogen- in eastern Tibet. The new age data further confirm that carbonatite– ic environment. The Permian paleorift zone, associated with the syenite magmatism within the EIACZ occurred after transition from a Emeishan LIP in southwestern China is generally regarded as a product transpressional to a transtensional regime at 38–42 Ma. Decompressional of mantle plume activity (Xu et al., 2001). However, by the end of the melting associated with the transtensional regime may have generated Mesozoic, the paleorift had apparently closed and became part of the the carbonatite–syenite magmas that ascended to shallow crustal levels Jinpingshan orogenic belt within the Cenozoic EIACZ (Burchfiel et al., via dilatational conduits developed during reactivation of the Permian 1995; Luo et al., 1998). paleorift zone in the late Oligocene–Miocene. During the transformation At least three significant geological formations in the EIACZ are rec- of the structural setting, previously formed faults bounding the Permian ognized as responses to Indian–Asian continent collision: (1) a series of paleorift zone in western Sichuan were reactivated, and operated as Cenozoic strike-slip fault systems (Wang et al., 2001b), reactivated fault strike-slip faults during the Oligocene–Miocene. This large-scale strike- systems (Guo et al., 2005) and large-scale shear zones (e.g., RRSZ, slip faulting formed a series of transtensional structures, such as pull- Tapponnier et al., 1990), along the eastern margin of the Tibetan apart basins, and tensional fissure zones, and may have facilitated the Plateau; (2) the early mid-Tertiary Lanping–Simao fold belt (Wang ascent and shallow-level emplacement of carbonatite–syenite magmas et al., 2001b) and Eocene pull-apart basins (Hou et al., 2003), bounded by providing the dilatational conduits. by the Cenozoic strike-slip faults; and (3) the Eocene–Oligocene potassic igneous province coeval with the Lanping–Simao fold belt and peaking at 35 Ma (Hou et al., 2006a). These three events provide impor- Acknowledgments tant constraints on the tectonic environment where the carbonatite– syenite complexes and associated REE mineralization are formed. We are grateful to Duan Lianfeng, Liang Wei and Li Qiuyun (CAGS), Wang et al. (2001b) proposed a tectonic model for the potassic rock who helped us obtain the SHRIMP II data. Constructive comments by belt in the RRSZ, in which eastward subduction of the Changdu–Simao two anonymous referees were very helpful and are highly appreciated. continental block along the RRSZ caused fluid infiltration into the over- The careful editorial handling, suggestions and comments of the Journal lying mantle wedge, triggering mantle melting to produce potassic Editor F.M. Pirajno and Managing Guest Editor Anton R. Chakhmouradian melts in a transpressional regime. It is clear that this local subduction are very helpful and are also gratefully appreciated. This study model does not provide a mechanism for the generation of the contem- was funded by the Major State Basic Research Program of China poraneous carbonatite–syenite and shoshonitic magmas in the EIACZ. (2009CB421008, 2011CB403100) and the Natural Science Founda- The broadly similar ages of the carbonatite–syenite complexes, potassic tion of China (Grant 41102039), IGCP/SIDA 600 project. rocks and shoshonitic lamprophyres imply that they share a common magma-generation mechanism, probably related to the ascent of a References Cenozoic asthenospheric mantle diaper, as inferred from geophysical studies (Zhong et al., 2001). With regard to the northeastward wedging Black, L.P., Kamo, S.L., Allen, C.M., Aleinikoff, J.N., Davis, D.W., Korsch, R.J., Foudoulis, C., 2003. Temorai: a new zircon standard for Phanerozoic U–Pb geochemistry. Chem. of the Indian continent (Fig. 1) and subsequent large-scale crustal short- Geol. 200, 155–170. ening and clockwise rotation (Wang and Burchfiel, 1997)ineastern Burchfiel, B.C., Zhi liang, Chen, Yu ping, Liu, Royden, L.H., 1995. Tectonics of the Longmen Tibet, it is postulated that this asthenospheric diapir was most likely Shan and adjacent regions, central China. Int. Geol. Rev. 37, 661–735. “ Cao, S.Y., Liu, J.L., Bernd, L., Franz, N., Johann, G., Zhao, J., Zhao, C.Q., 2011. Oligo-Miocene located beneath the EIACZ during the Eocene, and had an upright tile shearing along the Ailao Shan–Red River shear zone: constraints from structural sheet” shape extending along the western margin of the Yangtze craton analysis and zircon U/Pb geochronology of magmatic rocks in the Diancang Shan (Zhong et al., 2001). Its ascent could have triggered partial melting of a massif, SE Tibet, China. Gondwana Res. 19, 975–993. mantle source with enriched-mantle characteristics (EMI and EMII) un- Chen, K.X., 2006. The forming mechanism of copper-silver polymetallic ore concentrationarea in the north of Lanping foreland basin in Yunnan Province. derneath the EIACZ, in turn resulting in the formation of the Himalayan UnpublishedPh.D. dissertation, China University of Geosciences 160 pp; (in Chinese). carbonatites and alkaline rocks. Chung, S.L., Jahn, B.M., 1995. Plume–lithosphere interaction in generation of the Emeishan fl – – Decompressional melting is a plausible mechanism for the genera- ood basalts at the Permian Triassic boundary. Geology 23, 889 892. – Chung, S.L., Lo, C.H., Lee, T.Y., Zhang, Y.Q., Xie, Y.W., Li, X.H., Wang, K.L., Wang, P.L., 1998. tion of carbonatite syenitic magmas in the EIACZ and was probably Dischronous uplift of the Tibetan plateau starting from 40 Ma ago. Nature 349, related to a transition from a transpressional to a transtensional regime 769–773. during the Oligocene (40–38 Ma) (Hou et al., 2006a). This transition oc- Clark, M.K., Royden, L.H., 2000. Topographic ooze: building the eastern margin of Tibet by fl – – lower crustal ow. Geology 28, 703 706. curred before the main episode of magmatism (11 27 Ma) in the EIACZ, Compston, W., Williams, I.S., Kirschvink, J.L., Zhang, Z.C., Ma, G.G., 1992. Zircon U–Pb ages indicating that late- or post-collisional stress relaxation during the for the early Cambrian time-scale. J. Geol. Soc. Lond. 149, 171–184. 568 Y. Liu et al. / Ore Geology Reviews 64 (2015) 554–568

Cong, B.L., 1988. Formation and Evolution of the Panxi Paleo-rift. Science Press, Beijing Tang, R.L., Luo, H.S., 1995. The geology of Yulong porphyry copper (molybdenum) ore pp. 1–427 (in Chinese with English abstract). belt, Xizang (Tibet). Geological Publishing House, Beijing 320 pp; (in Chinese with Deng, J., Yang, L.Q., Gao, B.F., Sun, Z.S., Guo, C.Y., Wang, Q.F., Wang, Q.F., 2009. Fluid English abstract). evolution and metallogenic dynamics during tectonic regime transition: example Tapponnier, P., Lacassin, R., Leloup, P.H., Schärer, U., Zhong, D.L., Liu, X.H., Ji, S.C., Zhang, L. from the Jiapigou gold belt in northeast China. Resour. Geol. 59 (2), 140–152. S., Zhong, J.Y., 1990. The Ailao Shan/Red River metamorphic belt: tertiary left-lateral Deng, J., Wang, Q.F., Yang, S.J., Liu, X.F., Zhang, Q.Z., Yang, L.Q., Yang, Y.H., 2010a. Genetic shear between Indochina and South China. Nature 343 (1990), 431–437. relationship between the Emeishan plume and the bauxite deposits in Western Tian, S.H., 2005. The Himalayan Mianxi REE belt on the eastern margin of the Tibetan pla- Guangxi, China: constraints from U–Pb and Lu–Hf isotopes of the detrital zircons in teau: geology, geochemistry and geodynamics of the mineralization. Unpub. Ph. D bauxite ores. J. Asian Earth Sci. 37, 412–424. dissertation, Institute of Mineral Resources, CAGS, Beijing. 130 pp. (in Chinese with Deng, J., Wang, Q.F., Yang, L.Q., Wang, Y.R., Gong, Q.J., Liu, H., 2010b. Delineation and English abstract) exploration of geochemical anomalies using fractal models in the Heqing area, Tian, S.H., Hou, Z.Q., Yuan, Z.X., Chen, W., Xie, Y.L., Fei, H.C., Yin, S.P., Yi, L.S., Zhou, S., 2006. Yunnan Province, China. J. Geochem. Explor. 105 (3), 95–105. 40Ar/39Ar geochronology of rocks and ores from the Muluozhai REE deposit in Deng, J., Wang, Q.F., Xiao, C.H., Yang, L.Q., Liu, H., Gong, Q.J., Zhang, J., 2011. Tectonic– Mianning County, Sichuan Province. Acta Petrol. Sin. 22, 2431–2436. magmatic–metallogenic system, Tongling ore cluster region, Anhui Province, China. Tian, S.H., Hou, Z.Q., Yang, Z.S., Yang, Z.M., Yuan, Z.X., Wang, Y.B., Xie, Y.L., Liu, Y.C., Li, Z., Int. Geol. Rev. 53 (5–6), 449–476. 2008a. Zircon U–Pb ages, Hf isotopic compositions and geological significance: a Deng, J., Wang, Q.F., Li, G.J., Li, C.S., Wang, C.M., 2013. Tethys tectonic evolution and its case study of carbonatite and nordmarkite from the Dalucao REE deposit, Sichuan bearing on the distribution of important mineral deposits in the Sanjiang region, Province. Acta Petrol. Sin. 24, 544–554 (in Chinese with English abstract). SW China. Gondwana Res. http://dx.doi.org/10.1016/j.gr.2013.08.002. Tian, S.H., Hou, Z.Q., Yang, Z.S., Chen, W., Yang, Z.M., Yuan, Z.X., Xie, Y.L., Fei, H.C., Yin, S.P., Guo, Z.T., Hertogen, J., Liu, J.Q., Pasteels, P., Boven, A., Punzalan, L., He, H.Y., Luo, X.J., Zhang, Liu, Y.C., Li, Z., Li, X.Y., 2008b. Geochronology of REE deposits from the Mianning– W.H., 2005. Potassic magmatism in western Sichuan and Yunnan provinces, SE Tibet, Dechang REE belt: constraints on the duration of hydrothermal activities and a tec- China: petrological and geochemical constraints on petrogenesis. J. Petrol. 46, 33–78. tonic model for the carbonatite–alkalic complexes in Sichuan, SW China. Miner. He, L.Q., Song, Y.C., Chen, K.X., Hou, Z.Q., Yu, F.M., Yang, Z.S., Wei, J.Q., Li, Z., Liu, Y.C., 2009. Depos. 27, 177–187 (in Chinese with English abstract). Thrust-controlled, sediment-hosted, Himalayan Zn–Pb–Cu–Ag deposits in the Wang, E., Burchfiel, B.C., 1997. Interpretation of Cenozoic tectonics in the right-lateral ac- Lanping foreland fold belt, eastern margin of Tibetan Plateau. Ore Geol. Rev. 36, commodation zone between the Ailaoshan shear zone and the eastern Himalayan 106–132. syntaxis. Int. Geol. Rev. 39, 191–219. Hoskin, P.W.O., Black, L.P., 2000. Metamorphic zircon formation by solid-state recrystalli- Wang, J., Li, S.Q., 1992. Langshan–Baiyun Obo Rift of North China. Press of Peking Univer- zation of protolith igneous zircon. J. Metamorph. Geol. 18, 423–439. sity, Beijing pp. 1–20. Hou, Z.Q., Cook, N., 2009. Metallogenesis of the Tibetan collisional orogen: a review and Wang, D.H., Yang, J.M., Yan, S.H., Xu, J., Chen, Y.C., Pu, G.P., Luo, Y.N., 2001a. A special introduction to the special issue. Ore Geol. Rev. 36, 1–28. orogenic-type rare earth element deposit in Maoniuping, Sichuan, China: geology Hou, Z.Q., Ma, H.W., Zaw, K., Zhang, Y.Q., Wang, M.J., Wang, Z., Pan, G.T., 2003. The and geochemistry. Resour. Geol. 51, 177–188. Himalayan Yulong porphyry copper belt: product by large-scale strike-slip faulting Wang, J.H., Yin, A., Harrison, T.M., Grove, M., Zhang, Y.Q., Xie, G.H., 2001b. A tectonic in eastern Tibet. Econ. Geol. 98, 125–145. model for Cenozoic igneous activities in the eastern Indo-Asian collision zone. Earth Hou, Z.Q., Tian, S.H., Yuan, Z.X., Xie, Y.L., Yin, S.P., Yi, L.S., Fei, H.C., Yang, Z.M., 2006a. The Planet. Sci. Lett. 88, 123–133. Himalayan collision zone carbonatites in western Sichuan, SW China: petrogenesis, Wang, E., Kirby, E., Furlong, K.P., Soest, M.V., Xu, G., Shi, X., Kamp, P.J.J., Hodges, K.V., 2012. mantle source and tectonic implication. Earth Planet. Sci. Lett. 244, 234–250. Two-phase growth of high topography in eastern Tibet during the Cenozoic. Nat. Hou, Z.Q., Pan, G.T., Wang, A.J., Mo, X.X., Tian, S.H., Sun, X.M., Ding, L., Wang, E.Q., Gao, Y.F., Geosci. 5, 640–645. Xie, Y.L., Zeng, P.S., Qin, K.Z., Xu, J.F., Qu, X.M., Yang, Z.M., Yang, Z.S., Fei, H.C., Meng, X. Wu, Y.B., Zheng, Y.F., 2004. Genesis of zircon and its constraints on interpretation of U–Pb J., Li, Z.Q., 2006b. Metallogenesis in Tibetan collisional orogenic belt: II. Mineralization age. Chin. Sci. Bull. 49 (15), 1554–1569. in late-collisional transformation setting. Miner. Depos. 25, 521–543 (in Chinese with Xie, Y.L., Hou, Z.Q., Yin, S.P., Dominy, S.C., Xu, J.H., Tian, S.H., Xu, W.Y., 2009. Continuous English abstract). carbonatitic melt–fluid evolution of a REE mineralization system: evidence from in- Hou, Z.Q., Tian, S.H., Xie, Y.L., Yuan, Z.X., Yin, S.P., Yi, L.S., Fei, H.C., Zou, T.R., Bai, G., 2009. clusions in the Maoniuping REE deposit, western Sichuan, China. Ore Geol. Rev. 36, The Himalayan Mianning–Dechang REE belt associated with carbonatite–alkalic com- 90–105. plex in the eastern Indo-Asian collision zone, SW China. Ore Geol. Rev. 36, 65–89. Xu, D., Chen, Y., Zhang, Y., Li, W., Zhao, B., Luo, T., 1995. The study of the age and origin of Hu, Y.Z., Wang, H.P., Tang, S.Y., 1995. Geology of the Ailaoshan gold deposits. Geological the Kangding granitic complex, western Yangtze craton, China. Geol. Rev. 41, Publishing House, Beijing 278 pp; (in Chinese). 101–111 (in Chinese with English abstract). Liu, Z.Q., Li, X.Z., Ye, Q.T., Luo, J.N., Shen, G.F., Mo, X.X., Chen, F.Z., Chen, B.W., Yang, Y.Q., Lü, Xu, Y.G., Chung, S.L., Jahn, B.M., Wu, G.Y., 2001. Petrologic and geochemical constraints on B.X., Chen, J.S., Pan, G.T., Jia, B.J., Hu, Y.Z., Zheng, L.L., 1993. Division of the petrogenesis of Permain–Triassic Emeishan flood basalts in southwestern China. tectonomagmatic belts and distribution of the ore deposits in Sanjiang region. Geo- Lithos 58, 145–168. logical Publishing House, Beijing 243 pp; (in Chinese). Xu, C., Campbell, I.H., Kynicky, J., Allen, M.C., Chen, Y.J., Huang, Z.L., Qi, L., 2008. Compari- Lu, J.R., 1996. Dynamical characteristics of the Emei mantle plume. Acta Geosci. Sin. 17, son of the Daluxiang and Maoniuping carbonatitic REE deposits with Bayan Obo REE 424–438 (in Chinese with English abstract). deposits, China. Lithos 106, 12–24. Ludwig, K.R., 2001. Squid 1. 02: A User's Manual. No. 2. Berkeley Geochronology Center Xu, C., Taylor, R.N., Li, W.B., Kynicky, J., Chakhmouradian, A.R., Song, W.L., 2012. Compar- Special Publication pp. 1–21. ison of fluorite geochemistry from REE deposits in the Panxi region and Bayan Obo, Ludwig, K.R., 2003. User's Manual for Isoplot 3.00: A Geochronological Toolkit for China. J. Asian Earth Sci. 57, 76–89. Microsoft Excel. Berkeley Geochronology Center Special Publication, Berkeley. Xue, C.J., Zeng, R., Liu, S.W., Chi, G.X., Qing, H.R., Chen, Y.C., Yang, J.M., Wang, D.H., 2007. Luo, Y.N., Yu, R.L., 2001. Major features and dynamic model of the Himalayan tectonic– Geologic, fluid inclusion and isotopic characteristics of the Jinding Pb–Zn deposit, magmatism in the introcontinental orogenic belt in Longmenshan–Jinpingshan, western Yunnan, south China: a review. Ore Geol. Rev. 31, 337–359. Sichuan Province. In: Chen, Y.C., Wang, D.H. (Eds.), Study on Himalayan Endogenic Yang, G.M., Chang, C., Zuo, D.H., Liu, X.L., 1998. Geology and Mineralization of the Dalucao Mineralization. Seismological Press, Beijing, pp. 88–96 (in Chinese with English REE Deposit in Dechang County. Sichuan Province. Unpublished file of China Univer- abstract). sity of Geosciences, Wuhan pp. 1–89; (in Chinese). Luo, Y.N., Yu, R.L., Hou, L.W., Lai, S.M., Fu, D.M., Chen, M.X., Fu, X.F., Rao, R.B., Zhou, S.S., 1998. Yin, A., Harrison, T.M., 2000. Geologic evolution of the Himalayan Tibetan orogen. Annu. Longmenshan–Jinpingshan Intracontinental Orogenic Belt. Sichuan Science and Rev. Earth Planet. Sci. 28, 211–280. Technology Publishing House, Chengdu (171 pp., in Chinese with English abstract). Yuan, Z.X., Shi, Z.M., Bai, G., Wu, C.Y., Chi, R.A., Li, X.Y., 1995. The Maoniuping Rare Earth Mitchell, A.H.G., Garson, M.S., 1981. Mineral Deposits and Global Tectonic Settings. Ore Deposit, Mianning County, Sichuan Province. Seismological Press, Beijing (150 Academic Press, London (405 pp.). pp., in Chinese). Mo, X.X., Zhao, Z.D., Deng, J.F., Dong, G.C., Zhou, S., 2003. Response of volcanism to the India– Zhang, Y.Q., Xie, Y.W., 1997. Geochronology of alkali-rich intrusions and Nd, Sr isotopic Asia collision. Front. Earth Sci. China 10, 135–148 (in Chinese with English abstract). characteristics in Ailaoshan–Jinsha River. Sci. China Ser. E 27, 289–293. Nasdala, L., Hofmeister, W., Norberg, N., Mattinson, J.M., Corfu, F., Dor, W., Kamo, S.L., Zhang, Y.X., Luo, Y.N., Yang, C.X., 1988. The Panxi Rift. Geological Publishing House, Beijing Kennedy, A.K., Kronz, A., Reiners, P.W., Frei, D., Kosler, J., Wan, Y.S., Goze, J., Hoer, T., pp. 224–270 (in Chinese). Kröner, A., Valley, J.W., 2008. Zircon M257 — a homogeneous natural reference material Zhang, G.B., Song, S.G., Zhang, L.F., Niu, Y.L., 2008. The subducted oceanic crust within for the ion microprobe U–Pb analysis of zircon. Geostand. Geoanal. Res. 32, 247–265. continental-type UHP metamorphic belt in the North Qaidam, NW China: evidence Pu, G.P., 2001. The evolution history of rare earth elements mineralization and major fea- from petrology, geochemistry and geochronology. Lithos 104, 99–118. tures of Himalayan REE deposits in the Panzhihua–Xichang area, Sichuan. In: Chen, Y. Zheng, Y.C., Hou, Z.Q., Li, Q.Y., Sun, Q.Z., Liang, W., Fu, Q., Li, W., Huang, K.X., 2012. Origin of C., Wang, D.H. (Eds.), Study on Himalayan Endogenic Mineralization. Seismological late Oligocene adakitic intrusives in the southeastern Lhasa terrane: evidence from in Press, Beijing, pp. 104–116 (in Chinese with English abstract). situ zircon U–Pb dating, Hf–O isotopes, and whole-rock geochemistry. Lithos 148, Royden, L.H., Burchfiel, B.C., Kong, R.W., Wang, E., Chen, Z., Chen, F., Liu, Y., 1997. Surface 296–311. deformation and lower crustal flow in eastern Tibet. Science 276, 788–790. Zhong, D.L., Ding, L., Liu, F.T., Liu, J.H., Zhang, J.J., Ji, J.Q., Chen, H., 2001. The multidirection Stern, R.A., Amelin, Y., 2003. Assessment of errors in SIMS zircon U–Pb geochronology layer and frame structure of rock layers in orogenic belt and its control on Cenozoic using a natural zircon standard and NIST SRM 610 glass. Chem. Geol. 197, 111–142. magmatic activities: an example from Sanjiang and its neighboring area. Sci. China Sun, X., Deng, J., Zhao, Z.Y., Zhao, Z.H., Wang, Q.F., Yang, L.Q., Gong, Q.J., Wang, C.M., 2010. Ser. E 30, 1–8 (in Chinese). Geochronology, petrogenesis and tectonic implications of granites from the Fuxin area, Western Liaoning, NE China. Gondwana Res. 17, 642–652.