We extended the petrographic and geochemical data
set for the recently di
scovered Tran
santarctic Mountain microtektite
s in order to check our previou
s claim that they are related to the Au
strala
sian
strewn field. Ba
sed on color and compo
sition, the 465 microtektite
s so far identified include two group
s of tran
sparent gla
ss sphere
s le
ss than ca. 800 μm in diameter: the mo
st abundant pale-yellow, or normal, microtektite
s, and the rare pale-green, or high-Mg, microtektite
s. The major element compo
sition of normal microtektite
s determined through electron microprobe analy
si
s i
s characterized by high content
s of
silica (SiO<
sub>2
sub> = 71.5 ± 3.6 (1σ) wt % ) and alumina (Al<
sub>2
sub>O<
sub>3
sub> = 15.5 ± 2.2 (1σ) wt % ), low total alkali element content
s (0.50–1.85 wt % ), and MgO abundance
s <6 wt % . The high-Mg microtektite
s have a di
stinctly higher MgO content >10 wt % . Tran
santarctic Mountain microtektite
s contain rare
silica-rich (up to 93 wt % SiO<
sub>2
sub>) gla
ssy inclu
sion
s similar to tho
se found in two Au
strala
sian microtektite
s analyzed here for compari
son. The
se inclu
sion
s are interpreted a
s partially dige
sted, lechatelierite-like inclu
sion
s typically found in tektite
s and microtektite
s. The major and trace element (by la
ser ablation – inductively coupled pla
sma – ma
ss spectrometry) abundance pattern of the Tran
santarctic Mountain microtektite
s matche
s the average upper continental cru
st compo
sition for mo
st element
s. Major deviation
s include a
strong to moderate depletion in volatile element
s including Pb, Zn, Na, K, Rb, Sr and C
s, a
s a likely re
sult of
severe volatile lo
ss during the high temperature melting and vaporization of cru
stal target rock
s. The normal and high-Mg Tran
santarctic Mountain microtektite
s have compo
sition
s similar to the mo
st volatile-poor normal and high-Mg Au
strala
sian microtektite
s reported in the literature. Their very low H<
sub>2
sub>O and B content
s (by
secondary ion ma
ss spectrometry) of 85 ± 58 (1σ) μg/g and 0.53 ± 0.21 μg/g, re
spectively, evidence the extreme volatile lo
ss characteri
stically ob
served in tektite
s. The Sr and Nd i
sotopic compo
sition
s of multigrain
sample
s of Tran
santarctic Mountain microtektite
s are <
sup>87
sup>Sr/<
sup>86
sup>Sr ≈ 0.71629 and <
sup>143
sup>Nd/<
sup>144
sup>Nd ≈ 0.51209, and fall into the Au
strala
sian tektite compo
sitional field. The Nd model age calculated with re
spect to the chondritic uniform re
servoir (CHUR) i
s T<
sup>Nd
sup><
sub>CHUR
sub> ≈ 1.1 Ga, indicating a Me
so-Proterozoic cru
stal
source rock, a
s wa
s derived for Au
strala
sian tektite
s a
s well.
Coupled with the Quaternary age from the literature, the extended dataset presented in this work strengthens our previous conclusion that Transantarctic Mountain microtektites represent a major southward extension of the Australasian tektite/microtektite strewn field. Furthermore, the significant depletion in volatile elements (i.e., Pb, B, Na, K, Zn, Rb, Sr and Cs) of both normal and high-Mg Transantarctic Mountain microtektites relative to the Australasian ones provide us with further confirmation of a possible relationship between high temperature–time regimes in the microtektite-forming process and ejection distance.