Geochemical studies of tektites from East Asia

Abstract

Thirty tektites from East Asia (including Wenchang and Penglei of Hainan Island, Maoming of Guandong, China; Khon-Kaen of Thailand; Bao Loc of Vietnam; Rizal of Luzon, Philippines) have been analyzed for major and trace element contents and Rb-Sr isotopic compositions. All the samples studied are splash form tektites. The trace element ratios Ba/Rb (avg. 3.74), Th/Sm (avg. 2.31), Sm/Sc (avg. 0.43), Th/Sc (avg. 0.99) and the rare earth elements (REE) contents of tektites studied are similar to the average upper continental crust. The chemical data of tektites in this study indicate that they were derived from similar target rocks which may be related to post-Archean upper crustal materials. The tektites from East Asia have high positive ε Sr (0) values-ranging from 164.2 to 198.6, indicating that they were not dominantly derived from recent young sediments, such as soil or loess. The Ar-Ar ages (736.8 ± 55.5~814.6 ± 24.4 ka) of tektites of the present study are consistent with the age of other Australasian tektites, which indicates that all Australasian tektites were derived from a single impact event. Previous studies (Koeberl, 1992;Blum et al., 1992;Schnetzler, 1992) and the present chemical data suggest that these tektites are the result of melting at a single site, which is most probably located in the southern part of the Thailand-Laos border. Mixing calculations based on the model suggested by Ho and Chen (1996) for various amounts and combinations of target rocks indicate that the best fit for East Asia tektites is a mixture of 61% greywacke, 32% sandstone and 7% shale.

Geochemistry of Cenozoic microtektites and clinopyroxene-bearing spherules

“…Based on paleomagnetic studies, the Australasian tektite event appears to have taken place ϳ12-16 ka before the B/M reversal (Burns, 1989;Schneider et al, 1992;Lee and Wei, 2000), or ϳ0.8 Ma ago. This age is in agreement with the radiometric ages determined for the Australasian tektites (e.g., Izett and Obradovich, 1992;Kunz et al, 2000;Yamei et al, 2000;Lee et al, 2004). The Australasian strewn field covers nearly 10% of the Earth's surface.…”

Transantarctic Mountain microtektites: Geochemical affinity with Australasian microtektites

“…The Nd model ages of the Transantarctic Mountain microtektites point to a dominantly Meso-Proterozoic (1.6-1.0 Ga) crustal source material. The Sr-Nd isotope composition for the Transantarctic Mountain microtektites has been compared to the literature data for the other tektite strewn fields (Compston and Chapman, 1969;Shaw and Wassenburg, 1982;Blum et al, 1992;Lee et al, 2004;Deutsch and Koeberl, 2006). In the e CHUR (Nd)-e UR (Sr) diagram (Fig.…”

Geochemistry and origin of tektites from Guilin of Guangxi, Guangdong and Hainan

“…Figure 4 shows that there is a good correlation in the abundance of Rb, Mn, and Y between the tektite samples and the upper continental crust, but some trace elements are not closely correlated (i.e., Cr, Sr, Nb, and Ti). Many authors have used the CI-normalized ratios of the trace elements, such as Ba/Rb, Th/Sm, Th/Sc, Zr/Hf, and La/Lu to distinguish the provenance of tektites [10,11,13,23,28]. In Table 4, we list the CI-normalized ratios of Ba/Rb, Zr/Hf, and La/Lu for the southern China tektites, upper continental crust, low crust, oceanic crust, and primitive mantle.…”

“…Many researchers suggested that potential impact site for Australasian strewn field was probably located in the region near the southern part of the Thailand-Laos border, indochina [12,18,23,45], and this area lies within a broad region of Mesozoic marine sedimentary rocks. The exact target rocks from which Australasian tektites were produced have not yet been identified.…”

“…Tektites were previously found in Lingsui, Wenchang, Penglei, Dingan, Ledong, Qionghai, Zhanjiang, Maoming, Huazhou, Dibai, Suixi, Wuchuan, Bobai, Guiyang, Jingxi areas and so on [11,[22][23][24]. Previous reports on trace element compositions of bulk samples have been obtained by instrumental neutron activation analysis, inductively coupled plasma mass spectrometry, and atomic absorption spectrophotometer.…”