U–Pb dating of zircon and cassiterite from the Early Cretaceous Jiaojiguan iron-tin polymetallic deposit, implications for magmatism and metallogeny of the Tengchong area, western Yunnan, China

<p>The newly discovered Jiaojiguan deposit, a medium-scale skarn iron-tin polymetallic deposit on the Sino-Burma boundary of Yunnan Province (SW China), is spatially associated with the biotite monzonitic granite. Here, we report new <i>in situ</i> zircon LA-MC-ICP-MS U–Pb ages, trace element and Hf isotope data from the granite, and U–Pb dating ages of cassiterite from the ore bodies. In this study, we obtain a weighted mean ²⁰⁶Pb/²³⁸U age of 124.1 ± 1.4 Ma for the zircon and a ²⁰⁷Pb/²⁰⁶Pb-²³⁸U/²⁰⁶Pb intercept age of 123.8 ± 2.2 Ma for the cassiterite. The granite crystallized during the Early Cretaceous, with zircons exhibiting <i>ε</i>Hf(<i>t</i>) values from −5.8 to −0.6 and two-stage Hf model ages (T_DM2) of 1.21–1.54 Ga. The close temporal and spatial links between pluton emplacement and ore-forming events suggest that magmatic-hydrothermal events were the key factors that triggered the genesis of the iron-tin polymetallic deposits in the area. Regional geochronological data show that tin mineralization took place three times during the Cretaceous–Palaeogene in the Tengchong block due to re-melting of the underlying supposed Proterozoic (1.5 ± 0.5 Ga) Sn-rich strata/materials. Compared with those in the Bangong–Nujiang metallogenic belt (BNMB), we propose that the Cretaceous iron-tin polymetallic mineralization events in Tengchong–Baoshan closely resemble those of the Bangong–Nujiang belt in northern Tibet, both of which have experienced similar tectono-magmatic-metallogenic histories since the Mesozoic.</p

Endocrine disruptor levels in specimens (mg/L).

<p>Endocrine disruptor levels in specimens (mg/L).</p

Frequency distribution of MEHP levels in cord blood and meconium.

<p> The frequency distribution of MEHP levels in cord blood and meconium, illustrating that MEHP levels in meconium were much higher than those in cord blood.</p

Fetal-maternal ratios of EDs.

<p>The ratio of MEHP, OP, 4-NP BDE17-154, BDE183-209 and ∑PBDEs levels in the fetal and maternal circulation, showing that their levels were approximately 20% lower in cord blood samples than those in maternal blood samples.</p

Regression analysis between non-POPs levels in maternal and cord blood.

<p> Regression analysis was used to analyze the relationship between these EDs levels in maternal and cord blood. (A) The relationship between MEHP levels in maternal and cord blood. The regression coefficient was 0.807, meaning that about 80% MEHP could cross the placenta; (B) The relationship between OP levels in maternal and cord blood. The regression coefficient was 0.846, meaning that about 85% OP could go through the placenta; (C) The relationship between 4-NP levels in maternal and cord blood. The regression coefficient was 0.862, meaning that more than 86% 4-NP could cross the placenta.</p

Correlation between MEHP levels in cord blood and in meconium.

<p>MEHP was detected in 135 of 201 mother-newborn pairs, presenting a good correlation in cord blood and meconium.</p

Non-POPs levels in meconium specimens.

<p>The concentrations of MEHP, OP and 4-NP in meconium specimens.</p

PBDE levels in maternal blood and cord blood specimens (ng/g lipid).

<p>GM = geometric mean.</p>*<p>p<0.05.</p

Non-POPs levels in all specimens.

<p>The concentrations of MEHP, OP and 4-NP in maternal blood, cord blood and meconium specimens. And their levels in maternal blood were significantly higher than those in cord blood (p<0.0001).</p