2016年雅思閱讀長難句翻譯：同位素構(gòu)成

The isotopic composition of lead often varies from one source of common copper ore to another，with variations exceeding the measurement error;and preliminary studies indicate virtually uniform is topic composition of the lead from a single copper-ore source.
    鉛的同位素構(gòu)成經(jīng)常在一種普通銅礦石來源與另一種銅礦石來源之間存在差異，其差異程度超出測(cè)量誤差;而最初的研究表明，對(duì)于來自單獨(dú)一個(gè)銅礦石來源的鉛來說，其同位素構(gòu)成幾乎是毫無二致的。