青藏高原南北向裂谷启动时序的热年代学：以拉萨地体西部为例

王雨; 尼玛次仁; 刘海永; 张旭东

doi:10.19509/j.cnki.dzkq.tb20250377

青藏高原南北向裂谷启动时序的热年代学：以拉萨地体西部为例

doi: 10.19509/j.cnki.dzkq.tb20250377

王雨^1,,
尼玛次仁^1, ,,
刘海永^{1, 2},
张旭东^{1, 3}

西藏自治区地质调查院，拉萨 850000
西藏自治区地质矿产勘查开发局第二地质大队，拉萨 850000
西藏自治区地质矿产勘查开发局第五地质大队，青海格尔木 816000

基金项目: 中国矿产地质志项目（DD20221695；DD20190379；DD20160346）

详细信息

作者简介:
王雨：E-mail：wangyu_430@163.com

通讯作者:
E-mail：1940627805@qq.com

中图分类号: P542.3；P597⁺.3
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- 文章访问数: 328
- PDF下载量: 25
- 被引次数: 0
出版历程
- 收稿日期: 2025-08-13
- 录用日期: 2025-12-14
- 修回日期: 2025-11-13
- 网络出版日期: 2025-12-31

Thermochronologic study on initiation timing of north–south rift systems in Qinghai-Xizang Plateau: A case study of western Lhasa terrane

WANG Yu^1
,,
NIMA Ciren^{1
, ,},
LIU Haiyong^{1, 2},
ZHANG Xudong^{1, 3}

Xizang Autonomous Region Institute of Geological Survey, Lhasa 850000, China
The Second Geological Brigade of Xizang Autonomous Region Geological and Mineral Exploration and Development Bureau, Lhasa 850000, China
The Fifth Geological Brigade of Xizang Autonomous Region Geological and Mineral Exploration and Development Bureau, Golmud Qinghai 816000, China

More Information

Author Bio:
E-mail：wangyu_430@163.com

Corresponding author: E-mail：1940627805@qq.com

摘要

摘要:
青藏高原中新世以来南北向裂谷的形成机制与扩展规律是当前青藏高原综合研究的核心科学问题，对揭示高原深部动力学过程具有重要意义。目前对于单条南北向裂谷是自南向北抑或自北向南单向扩展仍存在较大争议。本研究聚焦拉萨地体西部隆格尔裂谷与当惹雍错−许如错裂谷，旨在约束2条裂谷南段的构造活动时限，并结合北段已发表热年代学数据，辨析裂谷沿走向的扩展规律，进一步揭示其深部动力学机制。采用锆石与磷灰石裂变径迹分析手段，对2条裂谷南段采集的冈底斯花岗岩及中新世碎屑砂岩开展低温热年代学研究；利用 HeFTy 软件开展蒙特卡洛热历史反演模拟，重建岩体冷却−剥露演化过程，为限定正断层的活动时代提供年代学约束。花岗岩样品锆石裂变径迹得到（25.9 ± 2.7） Ma 早中新世冷却年龄；磷灰石裂变径迹年龄主要集中在 12～10 Ma。热历史模拟揭示岩石在10～8 Ma之间发生显著快速冷却事件，冷却速率约为 50 ℃/Ma，对应的垂向抬升速率约为 2 km/Ma。结合北段已有热年代学数据对比，裂谷南、北段活动时间大体同步；碎屑磷灰石样品识别出（13.7 ± 2.0），（8.0 ± 2.9） Ma 2组剥露年龄峰值，指示源区多期构造剥露活动，未表现出自南向北或自北向南的单向扩展趋势。青藏高原南北向裂谷启动主要受控于印度板块撕裂引发的软流圈上涌以及中−下地壳流动产生的垂向浮力应力，裂谷的空间分布与印度岩石圈板片撕裂窗口不存在一一对应的空间匹配关系。裂谷形成记录了上地壳与下伏印度岩石圈由耦合向解耦转变的构造过程，建议重新审视传统的裂谷单向扩展模式。
- 青藏高原 /
- 南北向裂谷 /
- 裂变径迹 /
- 板片撕裂
Abstract:
Objective
The Miocene north-south rift systems within the Qinghai-Xizang Plateau represent a key expression of intracontinental east-west extension following the India-Eurasia collision, and investigating their initiation mechanism and along-strike propagation patterns is critical for deciphering deep lithospheric geodynamic processes. Two competing end-member hypotheses have been proposed for these rifts. One advocates north-to-south rift propagation, whereas the other supports south-to-north unidirectional expansion, and this controversy remains unresolved. This study focuses on the Lunggar Rift and the Dangre Yongcuo-Xuru Co Rift in the western Lhasa terrane. It aims to constrain the timing of tectonic activity along the southern segments of these two major rifts, compare the new results with published thermochronological datasets from their northern segments, discriminate the along-strike propagation behaviour, and further unravel the deep geodynamic driving forces.
Methods
Zircon and apatite fission-track low-temperature thermochronology was applied to Gangdese granite and Miocene clastic sandstone samples collected from the southern segments of the two rifts. Monte Carlo thermal-history inversion was implemented via the HeFTy software package to reconstruct the cooling-exhumation evolutionary paths of rocks and provide chronological constraints on the activation timing of normal faults.
Results
Zircon fission-track dating on granite samples yielded an early-Miocene cooling age of (25.9±2.7) Ma. Apatite fission-track ages were predominantly clustered within 12～10 Ma. Thermal-history modeling identified a prominent rapid-cooling episode during 12～10 Ma, with an estimated cooling rate of ～50 ℃/Ma and a corresponding vertical uplift rate of ～2 km/Ma. When integrated with previously published thermochronological results from northern rift segments, data from this study demonstrated roughly synchronous rift-related exhumation along strike. Detrital apatite fission-track analyses resolved two distinct exhumation age peaks at (13.7±2.0), (8.0±2.9) Ma, documenting multiphase tectonic exhumation of source terranes. No northward-only or southward-only unidirectional rift propagation was observed. The initiation of north-south rifts in the Qinghai-Xizang Plateau is predominantly driven by asthenospheric upwelling induced by Indian lithospheric slab tearing, together with vertical buoyancy stresses generated by middle-lower crustal flow. There is no one-to-one spatial correspondence between the surface distribution of rifts and deep slab-tear windows. The development of these rifts marks a critical tectonic transition from mechanical coupling to decoupling between the upper crust and the underthrust Indian lithosphere. Therefore, classical unidirectional rift-propagation models should be reconsidered.
Conclusion
This study provides new thermochronological constraints for understanding continental extensional deformation within collisional orogens of the Xizang-Himalayan system.
- Qinghai-Xizang Plateau /
- north-south rift /
- fission-track /
- slab tearing

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图 1 西藏南部构造简图（据文献[12]）

IYS. 雅鲁藏布缝合带；GCT. 大反冲断裂；STDS. 藏南拆离系；MCT. 主中央逆冲断裂；MBT. 主边界逆冲断裂；下同

Figure 1. Tectonic map of southern Xizang

下载: 全尺寸图片幻灯片

图 2 拉萨地体西部SN向裂谷及主要新生代岩石地层单元示意图

BNS. 班公湖−怒江缝合带；NLR. 北隆格尔裂谷；SLR. 南隆格尔裂谷；LPK. 冷布岗日裂谷；TYC. 当惹雍错裂谷

Figure 2. Schematic diagram of north-south rift systems and major Cenozoic lithostratigraphic units in western Lhasa terrane

下载: 全尺寸图片幻灯片

图 3 研究区地质简图(a, b)及野外照片(c, d)

a. 许如错裂谷南段；b. 帕龙错裂谷南段；c. 许如错断裂切断了大竹卡组砾岩（镜头朝西）；d. 帕龙错南端形成的近直立断层崖（镜头朝西）

Figure 3. Simplified geological maps (a, b) and field photographs (c, d) of study area

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图 4 裂变径迹样品14T11 HeFTy热历史模拟结果（GOF为拟合优度）

Figure 4. HeFTy thermal-history modeling results for fission-track sample 14T11

下载: 全尺寸图片幻灯片

表 1 碎屑磷灰石裂变径迹数据

Table 1. Detrital apatite fission-track data

样品编号	海拔/m	岩性	N	年龄范围/Ma	P(χ²)/%	D/%	年龄峰值P₁		年龄峰值P₂		中心年龄/Ma
样品编号	海拔/m	岩性	N	年龄范围/Ma	P(χ²)/%	D/%	年龄/Ma	占比/%	年龄/Ma	占比/%	中心年龄/Ma
CQ10-1	4923	砂岩	100	31.1～4.4	7.0	20.6	8.0±2.9	25.6	13.7±2.0	74.4	12.1±1.0
注：N为样品测试颗粒数；P(χ²)为自由度υ=N−1时χ²的概率值，当P(χ²)>5%，裂变径迹年龄代表单一组分年龄，否则为多组分年龄； D为年龄离散指数；下同

下载: 导出CSV

表 2 花岗岩锆石裂变径迹数据

Table 2. Zircon fission-track data of granite sample

样品编号	海拔/m	岩性	ρ_s/(条·cm⁻²)	N_s	ρ_i/(条·cm⁻²)	N_i	ρ_d/(条·cm⁻²)	N_d	N	P(χ²)/%	池年龄±2σ/Ma	w(U)±2σ/10⁻⁶
14T11	4935	闪长岩	3.25×10⁶	1017	1.99×10⁶	624	2.54×10⁵	3162	20	88.7	25.9±2.7	393±33
注：ρ_s和N_s分别为自发裂变径迹密度和径迹条数；ρ_i和N_i分别为诱发裂变径迹密度和径迹条数；ρ_d和N_d分别为标准玻璃径迹密度和径迹条数；2σ 为2倍标准偏差；下同

下载: 导出CSV

表 3 花岗岩磷灰石裂变径迹数据

Table 3. Apatite fission-track data of granite samples

样品编号	海拔/m	岩性	ρ_s/(条·cm⁻²)	N_s	ρ_i/(条·cm⁻²)	N_i	ρ_d/(条·cm⁻²)	N_d	N	P(χ²)/%	池年龄±2σ/Ma	w(U)±2σ/10⁻⁶	n	MTL ± 1σ/μm	标准偏差/μm
CQ8-1	5035	花岗岩	2.56×10⁵	328	2.94×10⁶	3760	1.21×10⁶	4101	20	79.3	13.0±1.6	37±2	11	13.84±0.4	1.40
14T11	4935	闪长岩	1.97×10⁵	184	2.90×10⁶	2703	1.09×10⁶	3474	25	93.8	9.2±1.4	40±2	42	13.47±0.3	1.63
注：n为裂变径迹长度测试条数；MTL为平均径迹长度；1σ为1倍标准偏差；σ为平均径迹长度标准差

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