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As fundamental parameters of the Antarctic Ice Sheet, ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica. During CHINARE 24 (the 24th Chinese National Antarctic Research Expedition, 2007/08), the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the 'Chinese Wall' around Kunlun Station, East Antarctica. Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the 'Chinese Wall', with the thickest ice being 3444 m, and the thinnest ice 1255 m. The average bedrock elevation is 1722 m, while the minimum is just 604 m. Compared with the northern side of the ice divide, the ice thickness is a little greater and the subglacial topography lower on the southern side, which is also characterized by four deep valleys. We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area, subglacial lakes, or water bodies along the 'Chinese Wall'. Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the 'Chinese Wall' are consistent with our results, but their resolution and accuracy are very limited in areas where the bedrock fluctuates intensely. The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifies the features of the ice sheet in this 'inaccessible' region. These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM's geological and deep ice core drilling sites in the Dome A region. [ABSTRACT FROM AUTHOR]

Highlights • Gneissic granites from Baoban Complex crystallized from a hybrid source of Paleoproterozoic crust and juvenile crust at ca. 1430 Ma. • Metasedimentary rocks from Baoban Complex rapid deposited at ca. 1460–1430 Ma. • Southwest Hainan had affinity with the East Antarctica in the Nuna. Abstract The Mesoproterozoic Baoban Complex, southwest Hainan Island, has played a crucial role in deciphering Nuna (Columbia) supercontinent reconstructions. Metasedimentary rocks in the Baoban Complex are intruded by Mesoproterozoic gneissic granites and mafic rocks. Our new geochemical and geochronological data show that these gneissic granites are monzogranites and granodiorites and crystallized at ∼1430 Ma. Geochemically, they are subdivided into two groups with I- and A-type affinities. The groups show broadly similar ε Nd (t) values ranging from −2.4 to +0.9, zircon ε Hf (t) from −5.4 to +7.8 and δ18O values from +5.0 to +8.6‰, suggesting derivation from the same source involving juvenile mafic melt and "ancient" continental crust components. Metasedimentary rocks have high La/Sc (1.4–5.8) but low Sc/Th (0.6–1.6) and Co/Th (0.3–1.1) ratios, as well as negative ε Nd (t) of −4.5 to −4.1, indicative of an "ancient" felsic igneous source with a recycled sedimentary component. Detrital zircon grains from the metasedimentary rocks yield three primary age-peaks of ∼1780 Ma, ∼1610 Ma and ∼1440 Ma, with the depositional age synchronous with those of the gneissic granites and metabasites (∼1430 Ma). Our geochemical and geochronological data, along with regional geological constraints, suggest a rift setting. The age populations and hafnium compositions of detrital zircons from the metasedimentary rocks in the Baoban Complex, southwest Hainan are comparable to those igneous zircons from East Antarctica, pointing out a probable affinity between southwest Hainan and East Antarctica in the Nuna supercontinent. [ABSTRACT FROM AUTHOR]