Abstract
Abstract In this study, we investigate the age and geochemical variability of volcanic arc rocks found in the Chinese, Kyrgyz, and Tajik North Pamir in Central Asia. New geochemical and geochronological data together with compiled data from the literature give a holistic view of an early to mid-Carboniferous intraoceanic arc preserved in the northeastern Pamir. This North Pamir volcanic arc complex involves continental slivers in its western reaches and transforms into a Cordilleran-style collision zone with arc-magmatic rocks. These are hosted in part by Devonian to Carboniferous oceanic crust and the metamorphic Kurguvad basement block of Ediacaran age (maximum deposition age) in Tajikistan. We discuss whether a sliver of Carboniferous subduction-related basalts and intruded tonalites close to the Chinese town of Mazar was part of the same arc. LA-ICP-MS U-Pb dating of zircons, together with whole rock geochemistry derived from tonalitic to granodioritic intrusions, reveals a major Visean to Bashkirian intrusive phase between 340 and 320 Ma ago. This clearly postdates Paleozoic arc-magmatic activity in the West Kunlun by ~100 Ma. This observation, along with geochemical evidence for a more pronounced mantle component in the Carboniferous arc-magmatic rocks of the North Pamir, disagrees with the common model of a continuous Kunlun belt from the West Kunlun into the North Pamir. Moreover, Paleozoic oceanic units younger than and west of the Tarim cratonic crust challenge the idea of a continuous cratonic Tarim-Tajik continent beneath the Pamir.
Highlights
A common model for plate tectonic reconstructions of northern Tibet and the Pamir has been the assumption of a continuous magmatic belt extending from the West Kunlun into the northern Pamir [1, 2]
Field investigations show that the North Pamir arc experienced three phases of volcanism and related igneous intrusions
The lower part of the sequence is characterized by finegrained greenish clastics; subordinate cross-bedded, red alluvial sandstones; and up to two-meter-thick lacustrine carbonate layers
Summary
A common model for plate tectonic reconstructions of northern Tibet and the Pamir has been the assumption of a continuous magmatic belt extending from the West Kunlun into the northern Pamir [1, 2]. Comparisons between the Paleozoic-early Mesozoic evolution of the poorly studied North Pamir and the adjacent, well-documented West Kunlun belt in northern Tibet reveal significant differences; these likely explain the different Cenozoic deformation styles of the adjacent regions. A common hypothesis is that the Pamir indented into the Tajik-Tarim basin in a late phase of the India-Asia collision, pushing the Pamir several hundred kilometers toward the north with respect to Tibet (e.g., Burtman and Molnar [1] and Schwab et al [3]).
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