Monday, May 21, 2007

Day 4: Looking into the world's largest open-pit mine

Monday, 30 April 2007. First, we went drove to the overlook point of the 4NE mine. This is the largest mine and has been in continual operation since commercial mining began in 1984. The scale of this one pit alone is impressive. It's sort of like standing on the edge of a man-made Grand Canyon. Okay, it's not quite that big, but still, considering it is basically a hole dug in the ground, it is large.


View from overlook point of N4E mine, Carajas, Brazil (click image for larger version)

Next we received hard hats and safety vests. Safety is of paramount concern in the mine. The mine trucks and digging machines make normal cars look like toys by comparison. Ever seen pictures of Bigfoot at a monster truck rally? Well, these mine trucks could roll over Bigfoot like Bigfoot rolls over normal cars. So staying out of their way and avoiding areas where they are blasting is goal #1.

After gawking at the N4E pit for a while, we moved onto the smaller N4W central pit. Since it is not actively being mined at the moment, it's a lot safer for us to scamper about. Spent rest of morning exploring highly dipping strata along western edge of pit.

After lunch at mine cafeteria (courtesy CVRD), we drove to several sites on a canga-covered plateau. "Canga" is a Brazilian turn for a type of deeply-weathered surface layer. As high volumes of rainwater percolate down into the ground, mobile elements are gradually stripped from upper layers, leaving a leeched cover of deeply weathered material. Anyway, on this particular plateau, Giliberto is overseeing systematic drilling program. The company is having drill cores extracted every 100 meters in a gridded pattern. Although time-consuming and undoubtedly expensive, such an intensive drilling program allows mining geologists and engineers to construct a highly detailed view of the subsurface rock strata and allows them to focus their efforts on the most worthwhile areas. Late in the afternoon we retired back to the field office to plan for the next day.

CVRD 6 meter drill rig on canga-covered plateau

Sunday, May 20, 2007

Day 3: Carajas background sessions

Sunday, 29 April 2007. Due to visa issues with one member of our group, we are limited to only 4 days at the mine site. So we decided to spent today at the mine offices in town and learn some background information about the mine from the company geologist, Gilberto De Lima Periera Silva. The full name of the mining company is "Companhia Vale do Rio Doce," or CVRD for short. CVRD was a state-run company until 1997, and it is now the 2nd largest diversified mining company in the world. Carajas is one of the biggest, if not the biggest, open pit mining complexes in the world. Production of iron ore was 81.8 million tons in 2006, and the goal for 2007 is 100 million tons. Raw ore is shipped by rail ~900 km to the port of Sao Lius, where is loaded onto massive cargo ships and sent to primarily Germany, China, and Japan for further processing.

Joel, the geologist whose PhD focus on Carajas, next gave us an overview of his research on the geology of Carajas. Carajas is a banded iron formation, or BIF for short. Banded iron formation are chemical sedimentary deposits, meaning that they were formed from minerals that precipitated out of a column of water. In this case, these deposits were laid down in a low energy, deep water (>100 m), oceanic setting. Banded iron formations are so named because they consist of alternating layers of silica and iron. The silica was most likely deposited as an ooze that was lain down from the continuous, slow deposition of amorphous silica gel particles. The iron layers, in contrast, were likely deposited rapidly. Ferrous iron (Fe 2+) dissolved in seawater under reducing conditions will precipitate rapidly when an oxidant, such as oxygen, is introduced.

So if you're thinking about Mars analogs, here's where things get interesting. Banded iron formations at Carajas date back some 2.7 billion years ago. Back when these things were being deposited, there wasn't a lot of oxygen present either in the ocean water or in the atmosphere. Oxygen-producing organisms were not yet abundant on Earth, so these BIFs were deposited under reducing conditions. As oxygen-producing photosynthetic cyanobacteria became more abundant, the oxygen they produced cause ocean-wide deposition of iron layers. A small fraction of these iron layers are preserved as banded iron formations. Perhaps early Mars, if ever clement enough to have standing bodies of water, experienced conditions similar to those recorded in these BIFs.

We spent the rest of the afternoon and evening laying out a field strategy for the coming days. Tomorrow, we'll get to see the mine and lay our hands on some 2.7 billion year old rocks!

Wednesday, May 16, 2007

Day 2: Drive into the Amazon

Saturday, 28 April 2007. Woke up at 5:30 am to catch our cab to the airport. We were a bit behind schedule since the cab driver, who usually drives to the other Sao Paulo airport (Guarulhos), took a wrong turn, but we made it to the Congohas Airport after only a slight delay.

The airport was an absolute madhouse. I wish I had taken a picture, but I was afraid that if I stopped moving I would have been trampled to death. Since the following Tuesday, May 1st is Labor Day (or International Workers Day), this is technically a holiday weekend. Add to that a multitude of weather-related delays and cancellations from yesterday, and it was enough to make the scene at the airport today look like something out of The Lord of the Flies. Luckily, we're traveling with two native Brazilian colleagues (Prof. Carlos Roberto de Souza Filho and Dr. Beatriz Ribeiro da Luz) who managed to get us checked in despite the madness. We flew from Sao Paulo to Brazilia and then to Maraba, a small river-front town in the Amazon Basin. Although we flew over the Carajas region, the could cover prevented us from seeing much. In Maraba, we picked up local geologist Joel Beunano, who did his PhD research in the Carajas mine. After that we boarded out rental car for the 3-4 hour drive to Carajas.

The drive to Carajas was not what I expected. We were driving southwest, deeper into the Amazon Basin. I was expecting a drive akin to a drive through the coastal redwood forest in Northern California, with huge trees lining a twisting roadway. Instead, we drove along a largely treeless, grassy plain that consisted mostly of farms and ranches. Clumps of trees on hills were visible here and there, as was the occasional lone Brazil nut tree, a protected species. The scale of the deforestation in this region is staggering, but upon further reflection is probably on par with that in the US. What fraction of pristine US forest remains? Less than 5%? 1%? I'm not sure of the exact number, but it's not a big number.

Blurry view out the window of the van. Note lone Brazil nut tree in center of otherwise treeless plain.


After our drive, we reached the town of Parauapebas and the gate to the Carajas mine. The mine (actually multiple mining sites) sit in a protected forest preserve. So it's weird that the best-preserved forest in this region is that under the protection of the mining company. Almost everything outside of the mine property has been cut down, while the mine itself is largely an untouched wilderness. Unfortunately it was dark when we arrived, I couldn't really tell how dense the jungle was past the mine gates. But we arrived at our hotel without further incident.

Thursday, May 10, 2007

Day 1: Getting there

Friday, 27 April 2007. After an overnight flight to Sao Paulo, Brazil, I can barely keep my eyes open. Luckily, me and my advisor at JPL, Dr. Nathan Bridges, were met at the airport by our colleagues Dr. Jim Crowley and his wife Dr. Beatriz Ribeiro da Luz. The plan was to spend the night at Jim & Beatriz's house in Sao Paulo before flying on the next day. So Jim & Beatriz picked us up in their car and wisked us off to their place across the city. Beatriz, a native Brazilian, drove. And is a damn good thing she did. Traffic in Brazil makes LA traffic look like a cakewalk; it makes Massholes from Boston seem like Mother Theresa. In addition to the regular traffic, madmen on motorcycles are constantly darting between lanes of cars and trucks. If owning a motorcycle in the US decreases your lifespan by an average of seven years, in Brazil it must decrease by at least 50 years. Yikes.

After a brief nap, we headed out for an early dinner. Early, that is, by Brazilian standards, where the typical evening meal starts no earlier than 9 pm. Most restaurants don't even open before 8 pm. After a hearty meal, we headed home early to get a jump on tomorrow. Onward to the Amazon!

Mars analogs in the Amazon jungle

Upon reading that title, you're probably wondering how in the heck the Amazon jungle is anything like Mars. The answer is, not much. But strip away the top 50-100 meters of material near Carajas, Brazil, and you'll find a banded iron formation, or BIF for short. BIFs are iron- rich chemical sediments deposited in a deep water (oceanic) setting some 2.7 billion years ago. About 98% of the world's supply of iron comes from deposits like these. I just returned from a trip to Brazil to study these amazing deposits with a group of fellow scientists. Our group is headed by Dr. Simon Hook of the Jet Propulsion Lab. You can check out the project's web site here: http://analogs.jpl.nasa.gov/.

I spent nine exciting days in Brazil, and I'll give you a day-by-day account here in my blog.