{"id":3079,"date":"2007-03-16T04:08:20","date_gmt":"2007-03-16T04:08:20","guid":{"rendered":"http:\/\/all-geo.org\/highlyallochthonous\/2007\/03\/want-to-know-about-monazite-then-phone-a-friend\/"},"modified":"2012-06-15T19:51:20","modified_gmt":"2012-06-16T00:51:20","slug":"want-to-know-about-monazite-then-phone-a-friend","status":"publish","type":"post","link":"https:\/\/all-geo.org\/highlyallochthonous\/2007\/03\/want-to-know-about-monazite-then-phone-a-friend\/","title":{"rendered":"Want to know about Monazite? Then phone a friend"},"content":{"rendered":"

At the beginning of the week, I came across this story<\/a>, about the new ‘Ultrachron’ machine (developed by Michael Williams and Michael Jercinovic at the University of Massachusetts), which seems to offer some exciting possibilities for extracting the detailed tectonic history of a rock<\/a>.
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The life of a rock is often filled with drama–there may be collisions, deforming pressures, intense heat or the scrape and weight of glaciers. Figuring out when something happened to a particular piece of rock has been difficult–methods exist for dating a rock’s absolute age–but scientists trying to determine the dates of a rock’s experiences have had to settle on ballpark figures often many millions of years apart.<\/p>\n

In the past decade however, researchers discovered that nature has a version of an airplane’s black box, in the form of a little-known mineral called monazite. Common in a wide variety of rocks, monazite contains uranium and thorium–elements that decay to lead over a predictable length of time–allowing scientists to read the ratios of these elements like a clock. Moreover, monazite grows in distinct layers, or “domains,” and a new domain is added each time the parent rock is altered, making the mineral a powerful tool for dating geologic processes, says Williams.<\/p>\n

“It grows a bit like an onion, a new layer is added each time the host rock undergoes some geologic event,” he says. When a new domain forms, its uranium clock begins ticking, so by carefully analyzing each domain in a fleck of monazite, the researchers can set dates to processes that affected the host rock–a collision or a period of melting, for example. “It’s acting like a petrologic tape recorder,” says Williams.<\/p>\n<\/blockquote>\n

It all sounds pretty exciting – and potentially important given the age of the rocks I’m getting started working on – but my first thought was, “is this for real?” (actually, my first thought was “what the heck is monazite?” – it’s a cerium (or other rare-earth metal) phosphate<\/a>, as it turns out). Unfortunately, my present understanding of dating techniques is not quite advanced to the point where I can see through the press release spin to the practicalities (and possible problems or uncertainties) with this method.<\/p>\n

However, thanks to my blogging, I know a man who does<\/a>. Lab Lemming has even explained the operating principles behind the ‘Ultrachron’ machine (an electron microprobe) and the differences between it and the ion microprobe<\/a> which is also used to analyse the composition of mineral grains in situ<\/i>. The verdict: if you have a system where U\/Th\/Pb loss is not a major problem, it should be OK for dating. And monazite is quite resistant to being reset – the domains represent growth of a new mineral during a metamorphic or tectonic event.<\/p>\n

And that, my friends, is why the geoblogosphere rocks.<\/p>\n","protected":false},"excerpt":{"rendered":"

At the beginning of the week, I came across this story, about the new ‘Ultrachron’ machine (developed by Michael Williams and Michael Jercinovic at the University of Massachusetts), which seems to offer some exciting possibilities for extracting the detailed tectonic … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,7,18],"tags":[],"class_list":["post-3079","post","type-post","status-publish","format-standard","hentry","category-geology","category-links","category-rocks-minerals"],"_links":{"self":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/3079","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/comments?post=3079"}],"version-history":[{"count":1,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/3079\/revisions"}],"predecessor-version":[{"id":7560,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/posts\/3079\/revisions\/7560"}],"wp:attachment":[{"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/media?parent=3079"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/categories?post=3079"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/all-geo.org\/highlyallochthonous\/wp-json\/wp\/v2\/tags?post=3079"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}