The India-Asia collision results from two possible pre-collisional crustal configurations of northern Greater India
The India-Asia collision results from two possible pre-collisional crustal configurations of northern Greater India
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DOI：
10.1016/j.epsl.2023.118098
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发表时间：
2023-05
影响因子：
5.3
通讯作者：
Yipeng Li;D. Robinson
中科院分区：
文献类型：
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作者：
Yipeng Li;D. Robinson
对大印度碰撞前构造的解释是非常有争议的，并预测了印度-亚洲碰撞期间的不同过程。为了更好地确定大印度可能的碰撞前构造，我们结合先前发表的地质，古地磁和地球动力学证据进行了质量平衡分析。质量平衡分析确定的大小北方大印度（NGI）的宽度需要提供足够的地壳增生形成特提斯-大喜马拉雅造山楔在新生代的时间。将10-40 km的端元地壳厚度应用到质量平衡方程中，得到了一个范围很广的合理的碰撞前NGI宽度，分别为3016±1000 km和956±283 km，我们进一步评估了对比模型/证据。综合证据要求NGI陆壳薄，形成1）连续的特提斯-大喜马拉雅地壳增厚，2）喜马拉雅前陆盆地狭窄的前渊宽度，3）连续的冈底斯弧岩浆活动和洋俯冲式地幔楔，4）北喜马拉雅和冈底斯弧-前弧低强度折返作用，时间为160 -30 Ma。综合分析表明，大印度南部可能存在两种构造格局：（1）宽1350±440 km，厚23-30 km的NGI，表明大印度南部可能存在宽2080±450 km，亚洲和NGI均存在宽500-1000 km的洋盆体系; 2）宽≥1815±630 km，厚10-23 km的Zealandia型NGI，表明存在一个宽≥2550±640 km的碰撞前大印度，不含或仅含约500-1000 km的日喀则弧后洋盆。前者假设NGI内没有新生代洋壳俯冲的启动，与综合证据有条件地一致，并预测了自160 Ma以来的多阶段碰撞。后者与综合证据相一致，并预测了大约60 Ma的单阶段碰撞。这两种配置预测显着的碰撞后NGI地壳缩短，可能已被容纳的始新世-渐新世大喜马拉雅构造不连续性。
Interpretations of pre-collisional configurations of Greater India are highly controversial and predict distinct processes during the India-Asia collision. To better determine the possible pre-collisional configuration(s) of Greater India, we conduct a mass-balance analysis combined with previously published geologic, paleomagnetic, and geodynamic evidence. The mass-balance analysis determines the magnitude of northern Greater India (NGI) width needed to provide sufficient crustal accretion to form the Tethyan-Greater Himalaya orogenic wedge in Cenozoic time. Applying endmember crustal thicknesses of 10–40 km to a mass-balance equation yields a broad range of plausible pre-collisional NGI widths of ∼3016±1000 km and ∼956±283 km, respectively, which we further assess considering contrasting models/evidence. The integrated evidence requires a thin NGI continental crust to form 1) continuous Tethyan-Greater Himalayan crustal thickening, 2) a narrow foredeep width of Himalayan foreland basin, 3) continuous Gangdese arc magmatism with oceanic-subduction-style mantle wedge, and 4) low-magnitude exhumation in the North Himalaya and Gangdese arc-forearc from ∼60-30 Ma. Adding the structurally restored ∼740 km wide southern Greater India, the synthesized analyses yield two possible configurations: 1) an ∼1350±440 km wide and ∼23-30 km thick NGI indicating an ∼2080±450 km wide Greater India with ∼500-1000 km wide oceanic basin systems in both Asia and NGI; and 2) a ≥1815±630 km wide and ∼10-23 km thick Zealandia-type NGI indicating a ≥2550±640 km wide pre-collisional Greater India without or with limited ∼500-1000 km Xigaze back-arc oceanic basin. The former is conditionally consistent with the integrated evidence by assuming no Cenozoic oceanic subduction initiation within NGI and predicts multi-stage collision since ∼60 Ma. The latter is consistent with the integrated evidence and predicts an approximate-single-stage collision at ∼60 Ma. Both configurations predict significant post-collisional NGI crustal shortening that may have been accommodated by the Eocene-Oligocene Greater Himalayan structural discontinuities.