加拿大發現地球上最古老岩石
The oldest rocks on Earth have been discovered in Canada, offering scientists a glimpse at the origins of the planet, announced scientists in a study to be published Friday.
The rocks, found in a belt of ancient bedrock in Quebec, are estimated to be 4.28 billion years old.
The find pushes back the age of the most ancient discovered remnants of the Earth's crust by 300 million years.
"Our discovery opens the door to further unlock the secrets of the Earth's beginnings," said Jonathan O'Neil, lead author of the study and a geologist at McGill University in Montreal, who collected and analyzed the rocks.
"Geologists now have a new playground to explore how and when life began, what the atmosphere may have looked like, and when the first continent formed," said O'Neil.
The rocks also suggest that continents formed very early in the Earth's history, said Richard Carlson at the Carnegie Institution in Washington, co-author of the study, to be published in the September 26 edition of the journal Science.
Estimates of the rocks' age were made using isotopic dating, a technique which can only be used to date rocks roughly 4.1 billion years old or older.
This is the first time the technique has been used to date terrestrial rocks, because nothing else this old has ever been discovered on Earth.
The specimens were found in an area known as the Nuvvuagittuq greenstone belt, along the eastern shore of Hudson Bay in northern Quebec, a region recognized in 2001 as being a potential site for finding ancient rocks.
科學家將於本週五發表的一項研究報告中公佈，他們在加拿大發現了目前地球上最古老的岩石，這一發現爲科學家研究地球起源提供了新的線索。
這些岩石是在加拿大魁北克省的一個古岩牀帶發現的，據估計距今已有42.8億年曆史。
這一發現將地殼最古老殘留物的年代又向前推了3億年。
研究報告主要撰寫者、蒙特利爾邁克基爾大學的地質學家喬納森•奧尼爾對這些岩石進行了收集和分析，他說：“我們的發現爲進一步探索地球的起源打開了一扇門。”
“地質學家現在有了一個新的平臺，去探究生命何時以及如何起源、當時的大氣狀況以及第一塊大陸何時形成等問題。”
研究報告撰寫者、華盛頓卡內基研究所的理查德•卡爾森說，這些岩石還說明，陸地在很早的時期就形成了。該研究在9月26日的《科學》期刊上發表。
這些岩石的年齡是經過“同位素測年法”測定出來的。同位素測年法只能夠用於測定至少有41億年曆史的岩石的年代。
這一方法首次被用於測定陸地岩石的年代，因爲之前在地球上還沒有發現過這麼古老的東西。
這些岩石發現於魁北克省北部哈德森灣東海岸沿線的Nuvvuagittuq 綠石帶。2001年，地質學家鑑定有望在這一地區發現古岩石。
